Grammar for MP3 files Sometimes the server from which a audio file is streamed is aware of transmission or coding problems resulting in interruptions in the audio stream. In these cases, the size of the buffer can be recommended by the server using this frame. If the 'embedded info flag' is true (1) then this indicates that an ID3 tag with the maximum size described in 'Buffer size' may occur in the audiostream. In such case the tag should reside between two MPEG [MPEG] frames, if the audio is MPEG encoded. If the position of the next tag is known, offset to next tag' may be used. The offset is calculated from the end of tag in which this frame resides to the first byte of the header in the next. This field may be omitted. Embedded tags is currently not recommended since this could render unpredictable behaviour from present software/hardware. The 'Buffer size' should be kept to a minimum. There may only be one "BUF" frame in each tag. This is simply a counter of the number of times a file has been played. The value is increased by one every time the file begins to play. There may only be one "CNT" frame in each tag. When the counter reaches all one's, one byte is inserted in front of the counter thus making the counter eight bits bigger. The counter must be at least 32-bits long to begin with. This frame replaces the old 30-character comment field in ID3v1. It consists of a frame head followed by encoding, language and content descriptors and is ended with the actual comment as a text string. Newline characters are allowed in the comment text string. There may be more than one comment frame in each tag, but only one with the same language and content descriptor. This frame indicates if the actual audio stream is encrypted, and by whom. Since standardisation of such encrypion scheme is beyond this document, all "CRA" frames begin with a terminated string with a URL containing an email address, or a link to a location where an email address can be found, that belongs to the organisation responsible for this specific encrypted audio file. Questions regarding the encrypted audio should be sent to the email address specified. If a $00 is found directly after the 'Frame size' and the audiofile indeed is encrypted, the whole file may be considered useless. After the 'Owner identifier', a pointer to an unencrypted part of the audio can be specified. The 'Preview start' and 'Preview length' is described in frames. If no part is unencrypted, these fields should be left zeroed. After the 'preview length' field follows optionally a datablock required for decryption of the audio. There may be more than one "CRA" frames in a tag, but only one with the same 'Owner identifier'. This frame contains one or more encrypted frames. This enables protection of copyrighted information such as pictures and text, that people might want to pay extra for. Since standardisation of such an encryption scheme is beyond this document, all "CRM" frames begin with a terminated string with a URL [URL] containing an email address, or a link to a location where an email adress can be found, that belongs to the organisation responsible for this specific encrypted meta frame. Questions regarding the encrypted frame should be sent to the indicated email address. If a $00 is found directly after the 'Frame size', the whole frame should be ignored, and preferably be removed. The 'Owner identifier' is then followed by a short content description and explanation as to why it's encrypted. After the 'content/explanation' description, the actual encrypted block follows. When an ID3v2 decoder encounters a "CRM" frame, it should send the datablock to the 'plugin' with the corresponding 'owner identifier' and expect to receive either a datablock with one or several ID3v2 frames after each other or an error. There may be more than one "CRM" frames in a tag, but only one with the same 'owner identifier'. This frame allows synchronisation with key events in a song or sound. This is another subjective, alignment frame. It allows the user to predefine an equalisation curve within the audio file. There may only be one "EQU" frame in each tag. In this frame any type of file can be encapsulated. After the header, 'Frame size' and 'Encoding' follows 'MIME type' [MIME] and 'Filename' for the encapsulated object, both represented as terminated strings encoded with ISO 8859-1 [ISO-8859-1]. The filename is case sensitive. Then follows a content description as terminated string, encoded as 'Encoding'. The last thing in the frame is the actual object. The first two strings may be omitted, leaving only their terminations. MIME type is always an ISO-8859-1 text string. There may be more than one "GEO" frame in each tag, but only one with the same content descriptor. Since there might be a lot of people contributing to an audio file in various ways, such as musicians and technicians, the 'Text information frames' are often insufficient to list everyone involved in a project. The 'Involved people list' is a frame containing the names of those involved, and how they were involved. The body simply contains a terminated string with the involvement directly followed by a terminated string with the involvee followed by a new involvement and so on. There may only be one "IPL" frame in each tag. To keep space waste as low as possible this frame may be used to link information from another ID3v2 tag that might reside in another audio file or alone in a binary file. It is recommended that this method is only used when the files are stored on a CD-ROM or other circumstances when the risk of file seperation is low. The frame contains a frame identifier, which is the frame that should be linked into this tag, a URL [URL] field, where a reference to the file where the frame is given, and additional ID data, if needed. Data should be retrieved from the first tag found in the file to which this link points. There may be more than one "LNK" frame in a tag, but only one with the same contents. A linked frame is to be considered as part of the tag and has the same restrictions as if it was a physical part of the tag (i.e. only one "REV" frame allowed, whether it's linked or not). Frames that may be linked and need no additional data are "IPL", "MCI", "ETC", "LLT", "STC", "RVA", "EQU", "REV", "BUF", the text information frames and the URL link frames. The "TXX", "PIC", "GEO", "CRM" and "CRA" frames may be linked with the content descriptor as additional ID data. The "COM", "SLT" and "ULT" frames may be linked with three bytes of language descriptor directly followed by a content descriptor as additional ID data. This frame is intended for music that comes from a CD, so that the CD can be identified in databases such as the CDDB [CDDB]. The frame consists of a binary dump of the Table Of Contents, TOC, from the CD, which is a header of 4 bytes and then 8 bytes/track on the CD making a maximum of 804 bytes. This frame requires a present and valid "TRK" frame. There may only be one "MCI" frame in each tag. To increase performance and accuracy of jumps within a MPEG [MPEG] audio file, frames with timecodes in different locations in the file might be useful. The ID3 frame includes references that the software can use to calculate positions in the file. After the frame header is a descriptor of how much the 'frame counter' should increase for every reference. If this value is two then the first reference points out the second frame, the 2nd reference the 4th frame, the 3rd reference the 6th frame etc. In a similar way the 'bytes between reference' and 'milliseconds between reference' points out bytes and milliseconds respectively. Each reference consists of two parts; a certain number of bits, as defined in 'bits for bytes deviation', that describes the difference between what is said in 'bytes between reference' and the reality and a certain number of bits, as defined in 'bits for milliseconds deviation', that describes the difference between what is said in 'milliseconds between reference' and the reality. The number of bits in every reference, i.e. 'bits for bytes deviation'+'bits for milliseconds deviation', must be a multiple of four. There may only be one "MLL" frame in each tag. This frame contains a picture directly related to the audio file. Image format is preferably "PNG" [PNG] or "JPG" [JFIF]. Description is a short description of the picture, represented as a terminated textstring. The description has a maximum length of 64 characters, but may be empty. There may be several pictures attached to one file, each in their individual "PIC" frame, but only one with the same content descriptor. There may only be one picture with the picture type declared as picture type $01 and $02 respectively. There is a possibility to put only a link to the image file by using the 'image format' "-->" and having a complete URL [URL] instead of picture data. The use of linked files should however be used restrictively since there is the risk of separation of files. The purpose of this frame is to specify how good an audio file is. Many interesting applications could be found to this frame such as a playlist that features better audiofiles more often than others or it could be used to profile a persons taste and find other 'good' files by comparing people's profiles. The frame is very simple. It contains the email address to the user, one rating byte and a four byte play counter, intended to be increased with one for every time the file is played. The email is a terminated string. The rating is 1-255 where 1 is worst and 255 is best. 0 is unknown. If no personal counter is wanted it may be omitted. When the counter reaches all one's, one byte is inserted in front of the counter thus making the counter eight bits bigger in the same away as the play counter ("CNT"). There may be more than one "POP" frame in each tag, but only one with the same email address. Yet another subjective one. You may here adjust echoes of different kinds. Reverb left/right is the delay between every bounce in ms. Reverb bounces left/right is the number of bounces that should be made. $FF equals an infinite number of bounces. Feedback is the amount of volume that should be returned to the next echo bounce. $00 is 0%, $FF is 100%. If this value were $7F, there would be 50% volume reduction on the first bounce, yet 50% on the second and so on. Left to left means the sound from the left bounce to be played in the left speaker, while left to right means sound from the left bounce to be played in the right speaker. 'Premix left to right' is the amount of left sound to be mixed in the right before any reverb is applied, where $00 id 0% and $FF is 100%. 'Premix right to left' does the same thing, but right to left. Setting both premix to $FF would result in a mono output (if the reverb is applied symmetric). There may only be one "REV" frame in each tag. This is a more subjective function than the previous ones. It allows the user to say how much he wants to increase/decrease the volume on each channel while the file is played. The purpose is to be able to align all files to a reference volume, so that you don't have to change the volume constantly. This frame may also be used to balance adjust the audio. If the volume peak levels are known then this could be described with the 'Peak volume right' and 'Peak volume left' field. If Peakvolume is not known these fields could be left zeroed or completely omitted. There may only be one "RVA" frame in each tag. This is another way of incorporating the words, said or sung lyrics, in the audio file as text, this time, however, in sync with the audio. It might also be used to describing events e.g. occurring on a stage or on the screen in sync with the audio. The header includes a content descriptor, represented with as terminated textstring. If no descriptor is entered, 'Content descriptor' is $00 (00) only. For a more accurate description of the tempo of a musical piece this frame might be used. After the header follows one byte describing which time stamp format should be used. Then follows one or more tempo codes. Each tempo code consists of one tempo part and one time part. The tempo is in BPM described with one or two bytes. If the first byte has the value $FF, one more byte follows, which is added to the first giving a range from 2 - 510 BPM, since $00 and $01 is reserved. $00 is used to describe a beat-free time period, which is not the same as a music-free time period. $01 is used to indicate one single beat-stroke followed by a beat-free period. The tempo descriptor is followed by a time stamp. Every time the tempo in the music changes, a tempo descriptor may indicate this for the player. All tempo descriptors should be sorted in chronological order. The first beat-stroke in a time-period is at the same time as the beat description occurs. There may only be one "STC" frame in each tag. The text information frames are the most important frames, containing information like artist, album and more. There may only be one text information frame of its kind in an tag. If the textstring is followed by a termination ($00 (00)) all the following information should be ignored and not be displayed. The 'Album/Movie/Show title' frame is intended for the title of the recording(/source of sound) which the audio in the file is taken from. BPM is short for beats per minute, and is easily computed by dividing the number of beats in a musical piece with its length. To get a more accurate result, do the BPM calculation on the main-part only. To acquire best result measure the time between each beat and calculate individual BPM for each beat and use the median value as result. BPM is an integer and represented as a numerical string. The 'Composer(s)' frame is intended for the name of the composer(s). They are seperated with the "/" character. The content type, which previously (in ID3v1.1, see appendix A) was stored as a one byte numeric value only, is now a numeric string. You may use one or several of the types as ID3v1.1 did or, since the category list would be impossible to maintain with accurate and up to date categories, define your own. References to the ID3v1 genres can be made by, as first byte, enter "(" followed by a number from the genres list (section A.3.) and ended with a ")" character. This is optionally followed by a refinement, e.g. "(21)" or "(4)Eurodisco". Several references can be made in the same frame, e.g. "(51)(39)". If the refinement should begin with a "(" character it should be replaced with "((", e.g. "((I can figure out any genre)" or "(55)((I think...)". The following new content types is defined in ID3v2 and is implemented in the same way as the numerig content types, e.g. "(RX)". RX Remix CR Cover The 'Copyright message' frame, which must begin with a year and a space character (making five characters), is intended for the copyright holder of the original sound, not the audio file itself. The absence of this frame means only that the copyright information is unavailable or has been removed, and must not be interpreted to mean that the sound is public domain. Every time this field is displayed the field must be preceded with "Copyright " (C) " ", where (C) is one character showing a C in a circle. The 'Date' frame is a numeric string in the DDMM format containing the date for the recording. This field is always four characters long. The 'Playlist delay' defines the numbers of milliseconds of silence between every song in a playlist. The player should use the "ETC" frame, if present, to skip initial silence and silence at the end of the audio to match the 'Playlist delay' time. The time is represented as a numeric string. The 'Encoded by' frame contains the name of the person or organisation that encoded the audio file. This field may contain a copyright message, if the audio file also is copyrighted by the encoder. The 'File type' frame indicates which type of audio this tag defines. The following type and refinements are defined: MPG MPEG Audio /1 MPEG 2 layer I /2 MPEG 2 layer II /3 MPEG 2 layer III /2.5 MPEG 2.5 /AAC Advanced audio compression but other types may be used, not for these types though. This is used in a similar way to the predefined types in the "TMT" frame, but without parenthesis. If this frame is not present audio type is assumed to be "MPG". The 'Time' frame is a numeric string in the HHMM format containing the time for the recording. This field is always four characters long. The 'Initial key' frame contains the musical key in which the sound starts. It is represented as a string with a maximum length of three characters. The ground keys are represented with "A","B","C","D","E", "F" and "G" and halfkeys represented with "b" and "#". Minor is represented as "m". Example "Cbm". Off key is represented with an "o" only. The 'Language(s)' frame should contain the languages of the text or lyrics in the audio file. The language is represented with three characters according to ISO-639-2. If more than one language is used in the text their language codes should follow according to their usage. The 'Length' frame contains the length of the audiofile in milliseconds, represented as a numeric string. The 'Media type' frame describes from which media the sound originated. This may be a textstring or a reference to the predefined media types found in the list below. References are made within "(" and ")" and are optionally followed by a text refinement, e.g. "(MC) with four channels". If a text refinement should begin with a "(" character it should be replaced with "((" in the same way as in the "TCO" frame. Predefined refinements is appended after the media type, e.g. "(CD/S)" or "(VID/PAL/VHS)". The 'Original artist(s)/performer(s)' frame is intended for the performer(s) of the original recording, if for example the music in the file should be a cover of a previously released song. The performers are seperated with the "/" character. The 'Original filename' frame contains the preferred filename for the file, since some media doesn't allow the desired length of the filename. The filename is case sensitive and includes its suffix. The 'Original Lyricist(s)/text writer(s)' frame is intended for the text writer(s) of the original recording, if for example the music in the file should be a cover of a previously released song. The text writers are seperated with the "/" character. The 'Original release year' frame is intended for the year when the original recording, if for example the music in the file should be a cover of a previously released song, was released. The field is formatted as in the "TDY" frame. The 'Original album/Movie/Show title' frame is intended for the title of the original recording(/source of sound), if for example the music in the file should be a cover of a previously released song. The 'Lead artist(s)/Lead performer(s)/Soloist(s)/Performing group' is used for the main artist(s). They are seperated with the "/" character. The 'Band/Orchestra/Accompaniment' frame is used for additional information about the performers in the recording. The 'Conductor' frame is used for the name of the conductor. The 'Interpreted, remixed, or otherwise modified by' frame contains more information about the people behind a remix and similar interpretations of another existing piece. The 'Part of a set' frame is a numeric string that describes which part of a set the audio came from. This frame is used if the source described in the "TAL" frame is divided into several mediums, e.g. a double CD. The value may be extended with a "/" character and a numeric string containing the total number of parts in the set. E.g. "1/2". The 'Publisher' frame simply contains the name of the label or publisher. The 'ISRC' frame should contian the International Standard Recording Code [ISRC]. The 'Recording dates' frame is a intended to be used as complement to the "TYE", "TDA" and "TIM" frames. E.g. "4th-7th June, 12th June" in combination with the "TYE" frame. The 'Track number/Position in set' frame is a numeric string containing the order number of the audio-file on its original recording. This may be extended with a "/" character and a numeric string containing the total numer of tracks/elements on the original recording. E.g. "4/9". The 'Size' frame contains the size of the audiofile in bytes excluding the tag, represented as a numeric string. The 'Software/hardware and settings used for encoding' frame includes the used audio encoder and its settings when the file was encoded. Hardware refers to hardware encoders, not the computer on which a program was run. The 'Content group description' frame is used if the sound belongs to a larger category of sounds/music. For example, classical music is often sorted in different musical sections (e.g. "Piano Concerto", "Weather - Hurricane"). The 'Title/Songname/Content description' frame is the actual name of the piece (e.g. "Adagio", "Hurricane Donna"). The 'Subtitle/Description refinement' frame is used for information directly related to the contents title (e.g. "Op. 16" or "Performed live at wembley"). The 'Lyricist(s)/text writer(s)' frame is intended for the writer(s) of the text or lyrics in the recording. They are seperated with the "/" character. This frame is intended for one-string text information concerning the audiofile in a similar way to the other "T"xx frames. The frame body consists of a description of the string, represented as a terminated string, followed by the actual string. There may be more than one "TXX" frame in each tag, but only one with the same description. The 'Year' frame is a numeric string with a year of the recording. This frames is always four characters long (until the year 10000). This frame's purpose is to be able to identify the audio file in a database that may contain more information relevant to the content. Since standardisation of such a database is beyond this document, all frames begin with a null-terminated string with a URL [URL] containing an email address, or a link to a location where an email address can be found, that belongs to the organisation responsible for this specific database implementation. Questions regarding the database should be sent to the indicated email address. The URL should not be used for the actual database queries. If a $00 is found directly after the 'Frame size' the whole frame should be ignored, and preferably be removed. The 'Owner identifier' is then followed by the actual identifier, which may be up to 64 bytes. There may be more than one "UFI" frame in a tag, but only one with the same 'Owner identifier'. This frame contains the lyrics of the song or a text transcription of other vocal activities. The head includes an encoding descriptor and a content descriptor. The body consists of the actual text. The 'Content descriptor' is a terminated string. If no descriptor is entered, 'Content descriptor' is $00 (00) only. Newline characters are allowed in the text. Maximum length for the descriptor is 64 bytes. There may be more than one lyrics/text frame in each tag, but only one with the same language and content descriptor. With these frames dynamic data such as webpages with touring information, price information or plain ordinary news can be added to the tag. There may only be one URL [URL] link frame of its kind in an tag, except when stated otherwise in the frame description. If the textstring is followed by a termination ($00 (00)) all the following information should be ignored and not be displayed. The 'Official audio file webpage' frame is a URL pointing at a file specific webpage. The 'Official artist/performer webpage' frame is a URL pointing at the artists official webpage. There may be more than one "WAR" frame in a tag if the audio contains more than one performer. The 'Official audio source webpage' frame is a URL pointing at the official webpage for the source of the audio file, e.g. a movie. The 'Commercial information' frame is a URL pointing at a webpage with information such as where the album can be bought. There may be more than one "WCM" frame in a tag. The 'Copyright/Legal information' frame is a URL pointing at a webpage where the terms of use and ownership of the file is described. The 'Publishers official webpage' frame is a URL pointing at the official web page for the publisher. This frame is intended for URL [URL] links concerning the audiofile in a similar way to the other "W"xx frames. The frame body consists of a description of the string, represented as a terminated string, followed by the actual URL. The URL is always encoded with ISO-8859-1 [ISO-8859-1]. There may be more than one "WXX" frame in each tag, but only one with the same description. This flag tells the software what to do with this frame if it is unknown and the tag is altered in any way. This applies to all kinds of alterations, including adding more padding and reordering the frames. This flag tells the software what to do with this frame if it is unknown and the file, excluding the tag, is altered. This does not apply when the audio is completely replaced with other audio data. This flag, if set, tells the software that the contents of this frame is intended to be read only. Changing the contents might break something, e.g. a signature. If the contents are changed, without knowledge in why the frame was flagged read only and without taking the proper means to compensate, e.g. recalculating the signature, the bit should be cleared. This flag indicates whether or not the frame is compressed This flag indicates wether or not the frame is enrypted. If set one byte indicating with which method it was encrypted will be appended to the frame header. This flag indicates whether or not this frame belongs in a group with other frames. If set a group identifier byte is added to the frame header. Every frame with the same group identifier belongs to the same group. This frame indicates if the actual audio stream is encrypted, and by whom. Since standardization of such encryption scheme is beyond this document, all "AENC" frames begin with a terminated string with a URL containing an email address, or a link to a location where an email address can be found, that belongs to the organisation responsible for this specific encrypted audio file. Questions regarding the encrypted audio should be sent to the email address specified. If a $00 is found directly after the 'Frame size' and the audiofile indeed is encrypted, the whole file may be considered useless. After the 'Owner identifier', a pointer to an unencrypted part of the audio can be specified. The 'Preview start' and 'Preview length' is described in frames. If no part is unencrypted, these fields should be left zeroed. After the 'preview length' field follows optionally a datablock required for decryption of the audio. There may be more than one "AENC" frames in a tag, but only one with the same 'Owner identifier'. This frame contains a picture directly related to the audio file. Image format is the MIME type and subtype for the image. In the event that the MIME media type name is omitted, "image/" will be implied. The "image/png" or "image/jpeg" picture format should be used when interoperability is wanted. Description is a short description of the picture, represented as a terminated textstring. The description has a maximum length of 64 characters, but may be empty. There may be several pictures attached to one file, each in their individual "APIC" frame, but only one with the same content descriptor. There may only be one picture with the picture type declared as picture type $01 and $02 respectively. There is the possibility to put only a link to the image file by using the 'MIME type' "-->" and having a complete URL instead of picture data. The use of linked files should however be used sparingly since there is the risk of separation of files. Audio files with variable bit rates are intrinsically difficult to deal with in the case of seeking within the file. The ASPI frame makes seeking easier by providing a list a seek points within the audio file. The seek points are a fractional offset within the audio data, providing a starting point from which to find an appropriate point to start decoding. The presence of an ASPI frame requires the existence of a TLEN frame, indicating the duration of the file in milliseconds. There may only be one 'audio seek point index' frame in a tag. 'Indexed data start' is a byte offset from the beginning of the file. 'Indexed data length' is the byte length of the audio data being indexed. 'Number of index points' is the number of index points, as the name implies. The recommended number is 100. 'Bits per index point' is 8 or 16, depending on the chosen precision. 8 bits works well for short files (less than 5 minutes of audio), while 16 bits is advantageous for long files. 'Fraction at index' is the numerator of the fraction representing a relative position in the data. The denominator is 2 to the power of b. Here are the algorithms to be used in the calculation. The known data must be the offset of the start of the indexed data (S), the offset of the end of the indexed data (E), the number of index points (N), the offset at index i (Oi). We calculate the fraction at index i (Fi). Oi is the offset of the frame whose start is soonest after the point for which the time offset is (i/N * duration). The frame data should be calculated as follows: Fi = Oi/L * 2^b (rounded down to the nearest integer) Offset calculation should be calculated as follows from data in the frame: Oi = (Fi/2^b)*L (rounded up to the nearest integer) This frame is indended for any kind of full text information that does not fit in any other frame. It consists of a frame header followed by encoding, language and content descriptors and is ended with the actual comment as a text string. Newline characters are allowed in the comment text string. There may be more than one comment frame in each tag, but only one with the same language and content descriptor. This frame enables several competing offers in the same tag by bundling all needed information. That makes this frame rather complex but it's an easier solution than if one tries to achieve the same result with several frames. The frame begins, after the frame ID, size and encoding fields, with a price string field. A price is constructed by one three character currency code, encoded according to ISO-4217 alphabetic currency code, followed by a numerical value where "." is used as decimal seperator. In the price string several prices may be concatenated, seperated by a "/" character, but there may only be one currency of each type. The price string is followed by an 8 character date string in the format YYYYMMDD, describing for how long the price is valid. After that is a contact URL, with which the user can contact the seller, followed by a one byte 'received as' field. Next follows a terminated string with the name of the seller followed by a terminated string with a short description of the product. The last thing is the ability to include a company logotype. The first of them is the 'Picture MIME type' field containing information about which picture format is used. In the event that the MIME media type name is omitted, "image/" will be implied. Currently only "image/png" and "image/jpeg" are allowed. This format string is followed by the binary picture data. This two last fields may be omitted if no picture is to attach. To identify with which method a frame has been encrypted the encryption method must be registered in the tag with this frame. The 'Owner identifier' is a null-terminated string with a URL containing an email address, or a link to a location where an email address can be found, that belongs to the organisation responsible for this specific encryption method. Questions regarding the encryption method should be sent to the indicated email address. The 'Method symbol' contains a value that is associated with this method throughout the whole tag. Values below $80 are reserved. The 'Method symbol' may optionally be followed by encryption specific data. There may be several "ENCR" frames in a tag but only one containing the same symbol and only one containing the same owner identifier. The method must be used somewhere in the tag. This is another subjective, alignment frame. It allows the user to predefine an equalisation curve within the audio file. There may only be one "EQUA" frame in each tag. The 'adjustment bits' field defines the number of bits used for representation of the adjustment. This is normally $10 (16 bits) for MPEG 2 layer I, II and III and MPEG 2.5. This value may not be $00. This is followed by 2 bytes + ('adjustment bits' rounded up to the nearest byte) for every equalisation band in the following format, giving a frequency range of 0 - 32767Hz The increment/decrement bit is 1 for increment and 0 for decrement. The equalisation bands should be ordered increasingly with reference to frequency. All frequencies don't have to be declared. The equalisation curve in the reading software should be interpolated between the values in this frame. Three equal adjustments for three subsequent frequencies. A frequency should only be described once in the frame. This is another subjective, alignment frame. It allows the user to predefine an equalisation curve within the audio file. There may be more than one "EQU2" frame in each tag, but only one with the same identification string. The 'interpolation method' describes which method is preferred when an interpolation between the adjustment point that follows. The following methods are currently defined: $00 Band No interpolation is made. A jump from one adjustment level to another occurs in the middle between two adjustment points. $01 Linear Interpolation between adjustment points is linear. The 'identification' string is used to identify the situation and/or device where this adjustment should apply. The following is then repeated for every adjustment point Frequency $xx xx Volume adjustment $xx xx The frequency is stored in units of 1/2 Hz, giving it a range from 0 to 32767 Hz. The volume adjustment is encoded as a fixed point decibel value, 16 bit signed integer representing (adjustment*512), giving +/- 64 dB with a precision of 0.001953125 dB. E.g. +2 dB is stored as $04 00 and -2 dB is $FC 00. Adjustment points should be ordered by frequency and one frequency should only be described once in the frame. The 'interpolation method' describes which method is preferred when an interpolation between the adjustment point that follows. The following methods are currently defined: $00 Band No interpolation is made. A jump from one adjustment level to another occurs in the middle between two adjustment points. $01 Linear Interpolation between adjustment points is linear. The 'identification' string is used to identify the situation and/or device where this adjustment should apply. Adjustment points should be ordered by frequency and one frequency should only be described once in the frame. The frequency is stored in units of 1/2 Hz, giving it a range from 0 to 32767 Hz. The volume adjustment is encoded as a fixed point decibel value, 16 bit signed integer representing (adjustment*512), giving +/- 64 dB with a precision of 0.001953125 dB. E.g. +2 dB is stored as $04 00 and -2 dB is $FC 00. This frame allows synchronisation with key events in a song or sound. Terminating the start events such as "intro start" is not required. The 'Not predefined sync's ($E0-EF) are for user events. You might want to synchronise your music to something, like setting of an explosion on-stage, turning on your screensaver etc. There may only be one "ETCO" frame in each tag. In this frame any type of file can be encapsulated. After the header, 'Frame size' and 'Encoding' follows 'MIME type' represented as as a terminated string encoded with ISO-8859-1. The filename is case sensitive and is encoded as 'Encoding'. Then follows a content description as terminated string, encoded as 'Encoding'. The last thing in the frame is the actual object. The first two strings may be omitted, leaving only their terminations. There may be more than one "GEOB" frame in each tag, but only one with the same content descriptor. This frame enables grouping of otherwise unrelated frames. This can be used when some frames are to be signed. To identify which frames belongs to a set of frames a group identifier must be registered in the tag with this frame. The 'Owner identifier' is a null-terminated string with a URL containing an email address, or a link to a location where an email address can be found, that belongs to the organisation responsible for this grouping. Questions regarding the grouping should be sent to the indicated email address. The 'Group symbol' contains a value that associates the frame with this group throughout the whole tag. Values below $80 are reserved. The 'Group symbol' may optionally be followed by some group specific data, e.g. a digital signature. There may be several "GRID" frames in a tag but only one containing the same symbol and only one containing the same owner identifier. The group symbol must be used somewhere in the tag. Since there might be a lot of people contributing to an audio file in various ways, such as musicians and technicians, the 'Text information frames' are often insufficient to list everyone involved in a project. The 'Involved people list' is a frame containing the names of those involved, and how they were involved. The body simply contains a terminated string with the involvement directly followed by a terminated string with the involvee followed by a new involvement and so on. There may only be one "IPLS" frame in each tag. To keep space waste as low as possible this frame may be used to link information from another ID3v2 tag that might reside in another audio file or alone in a binary file. It is recommended that this method is only used when the files are stored on a CD-ROM or other circumstances when the risk of file seperation is low. The frame contains a frame identifier, which is the frame that should be linked into this tag, a URL field, where a reference to the file where the frame is given, and additional ID data, if needed. Data should be retrieved from the first tag found in the file to which this link points. There may be more than one "LINK" frame in a tag, but only one with the same contents. A linked frame is to be considered as part of the tag and has the same restrictions as if it was a physical part of the tag (i.e. only one "RVRB" frame allowed, whether it's linked or not). Frames that may be linked and need no additional data are "IPLS", "MCID", "ETCO", "MLLT", "SYTC", "RVAD", "EQUA", "RVRB", "RBUF", the text information frames and the URL link frames. The "TXXX", "APIC", "GEOB" and "AENC" frames may be linked with the content descriptor as additional ID data. The "COMM", "SYLT" and "USLT" frames may be linked with three bytes of language descriptor directly followed by a content descriptor as additional ID data. This frame is intended for music that comes from a CD, so that the CD can be identified in databases such as the CDDB. The frame consists of a binary dump of the Table Of Contents, TOC, from the CD, which is a header of 4 bytes and then 8 bytes/track on the CD plus 8 bytes for the 'lead out' making a maximum of 804 bytes. The offset to the beginning of every track on the CD should be described with a four bytes absolute CD-frame address per track, and not with absolute time. This frame requires a present and valid "TRCK" frame, even if the CD's only got one track. There may only be one "MCDI" frame in each tag. To increase performance and accuracy of jumps within a MPEG audio file, frames with timecodes in different locations in the file might be useful. The ID3v2 frame includes references that the software can use to calculate positions in the file. After the frame header is a descriptor of how much the 'frame counter' should increase for every reference. If this value is two then the first reference points out the second frame, the 2nd reference the 4th frame, the 3rd reference the 6th frame etc. In a similar way the 'bytes between reference' and 'milliseconds between reference' points out bytes and milliseconds respectively. Each reference consists of two parts; a certain number of bits, as defined in 'bits for bytes deviation', that describes the difference between what is said in 'bytes between reference' and the reality and a certain number of bits, as defined in 'bits for milliseconds deviation', that describes the difference between what is said in 'milliseconds between reference' and the reality. The number of bits in every reference, i.e. 'bits for bytes deviation'+'bits for milliseconds deviation', must be a multiple of four. There may only be one "MLLT" frame in each tag. The ownership frame might be used as a reminder of a made transaction or, if signed, as proof. Note that the "USER" and "TOWN" frames are good to use in conjunction with this one. The frame begins, after the frame ID, size and encoding fields, with a 'price payed' field. The first three characters of this field contains the currency used for the transaction, encoded according to ISO-4217 alphabetic currency code. Concatenated to this is the actual price payed, as a numerical string using "." as the decimal separator. Next is an 8 character date string (YYYYMMDD) followed by a string with the name of the seller as the last field in the frame. There may only be one "OWNE" frame in a tag. This frame is used to contain information from a software producer that its program uses and does not fit into the other frames. The frame consists of an 'Owner identifier' string and the binary data. The 'Owner identifier' is a null-terminated string with a URL containing an email address, or a link to a location where an email address can be found, that belongs to the organisation responsible for the frame. Questions regarding the frame should be sent to the indicated email address. The tag may contain more than one "PRIV" frame but only with different contents. It is recommended to keep the number of "PRIV" frames as low as possible. This is simply a counter of the number of times a file has been played. The value is increased by one every time the file begins to play. There may only be one "PCNT" frame in each tag. When the counter reaches all one's, one byte is inserted in front of the counter thus making the counter eight bits bigger. The counter must be at least 32-bits long to begin with. The purpose of this frame is to specify how good an audio file is. Many interesting applications could be found to this frame such as a playlist that features better audiofiles more often than others or it could be used to profile a person's taste and find other 'good' files by comparing people's profiles. The frame is very simple. It contains the email address to the user, one rating byte and a four byte play counter, intended to be increased with one for every time the file is played. The email is a terminated string. The rating is 1-255 where 1 is worst and 255 is best. 0 is unknown. If no personal counter is wanted it may be omitted. When the counter reaches all one's, one byte is inserted in front of the counter thus making the counter eight bits bigger in the same away as the play counter ("PCNT"). There may be more than one "POPM" frame in each tag, but only one with the same email address. This frame delivers information to the listener of how far into the audio stream he picked up; in effect, it states the time offset of the first frame in the stream.# If this frame is used in the beginning of a file the value is always 0. There may only be one "POSS" frame in each tag. Sometimes the server from which a audio file is streamed is aware of transmission or coding problems resulting in interruptions in the audio stream. In these cases, the size of the buffer can be recommended by the server using this frame. If the 'embedded info flag' is true (1) then this indicates that an ID3 tag with the maximum size described in 'Buffer size' may occur in the audiostream. In such case the tag should reside between two MPEG frames, if the audio is MPEG encoded. If the position of the next tag is known, 'offset to next tag' may be used. The offset is calculated from the end of tag in which this frame resides to the first byte of the header in the next. This field may be omitted. Embedded tags are generally not recommended since this could render unpredictable behaviour from present software/hardware. For applications like streaming audio it might be an idea to embed tags into the audio stream though. If the clients connects to individual connections like HTTP and there is a possibility to begin every transmission with a tag, then this tag should include a 'recommended buffer size' frame. If the client is connected to a arbitrary point in the stream, such as radio or multicast, then the 'recommended buffer size' frame should be included in every tag. Every tag that is picked up after the initial/first tag is to be considered as an update of the previous one. E.g. if there is a "TIT2" frame in the first received tag and one in the second tag, then the first should be 'replaced' with the second. The 'Buffer size' should be kept to a minimum. There may only be one "RBUF" frame in each tag. This is a more subjective function than the previous ones. It allows the user to say how much he wants to increase/decrease the volume on each channel while the file is played. The purpose is to be able to align all files to a reference volume, so that you don't have to change the volume constantly. This frame may also be used to balance adjust the audio. If the volume peak levels are known then this could be described with the 'Peak volume right' and 'Peak volume left' field. If Peakvolume is not known these fields could be left zeroed or, if no other data follows, be completely omitted. There may only be one "RVAD" frame in each tag. In the increment/decrement field bit 0 is used to indicate the right channel and bit 1 is used to indicate the left channel. 1 is increment and 0 is decrement. The 'bits used for volume description' field is normally $10 (16 bits) for MPEG 2 layer I, II and III and MPEG 2.5. This value may not be $00. The volume is always represented with whole bytes, padded in the beginning (highest bits) when 'bits used for volume description' is not a multiple of eight. This datablock is then optionally followed by a volume definition for the left and right back channels. If this information is appended to the frame the first two channels will be treated as front channels. In the increment/decrement field bit 2 is used to indicate the right back channel and bit 3 for the left back channel. If the center channel adjustment is present the following is appended to the existing frame, after the left and right back channels. The center channel is represented by bit 4 in the increase/decrease field. If the bass channel adjustment is present the following is appended to the existing frame, after the center channel. The bass channel is represented by bit 5 in the increase/decrease field. This is a more subjective frame than the previous ones. It allows the user to say how much he wants to increase/decrease the volume on each channel when the file is played. The purpose is to be able to align all files to a reference volume, so that you don't have to change the volume constantly. This frame may also be used to balance adjust the audio. The volume adjustment is encoded as a fixed point decibel value, 16 bit signed integer representing (adjustment*512), giving +/- 64 dB with a precision of 0.001953125 dB. E.g. +2 dB is stored as $04 00 and -2 dB is $FC 00. There may be more than one "RVA2" frame in each tag, but only one with the same identification string. The 'identification' string is used to identify the situation and/or device where this adjustment should apply. The following is then repeated for every channel Bits representing peak can be any number between 0 and 255. 0 means that there is no peak volume field. The peak volume field is always padded to whole bytes, setting the most significant bits to zero. The 'identification' string is used to identify the situation and/or device where this adjustment should apply. Bits representing peak can be any number between 0 and 255. 0 means that there is no peak volume field. The peak volume field is always padded to whole bytes, setting the most significant bits to zero. Yet another subjective one. You may here adjust echoes of different kinds. Reverb left/right is the delay between every bounce in ms. Reverb bounces left/right is the number of bounces that should be made. $FF equals an infinite number of bounces. Feedback is the amount of volume that should be returned to the next echo bounce. $00 is 0%, $FF is 100%. If this value were $7F, there would be 50% volume reduction on the first bounce, 50% of that on the second and so on. Left to left means the sound from the left bounce to be played in the left speaker, while left to right means sound from the left bounce to be played in the right speaker. 'Premix left to right' is the amount of left sound to be mixed in the right before any reverb is applied, where $00 id 0% and $FF is 100%. 'Premix right to left' does the same thing, but right to left. Setting both premix to $FF would result in a mono output (if the reverb is applied symmetric). There may only be one "RVRB" frame in each tag. This frame indicates where other tags in a file/stream can be found. The 'minimum offset to next tag' is calculated from the end of this tag to the beginning of the next. There may only be one 'seek frame' in a tag. This frame enables a group of frames, grouped with the 'Group identification registration', to be signed. Although signatures can reside inside the registration frame, it might be desired to store the signature elsewhere, e.g. in watermarks. There may be more than one 'signature frame' in a tag, but no two may be identical. This is another way of incorporating the words, said or sung lyrics, in the audio file as text, this time, however, in sync with the audio. It might also be used to describing events e.g. occurring on a stage or on the screen in sync with the audio. The header includes a content descriptor, represented with as terminated textstring. If no descriptor is entered, 'Content descriptor' is $00 (00) only. The text that follows the frame header differs from that of the unsynchronised lyrics/text transcription in one major way. Each syllable (or whatever size of text is considered to be convenient by the encoder) is a null terminated string followed by a time stamp denoting where in the sound file it belongs. The 'time stamp' is set to zero or the whole sync is omitted if located directly at the beginning of the sound. All time stamps should be sorted in chronological order. The sync can be considered as a validator of the subsequent string. Newline ($0A) characters are allowed in all "SYLT" frames and should be used after every entry (name, event etc.) in a frame with the content type $03 - $04. A few considerations regarding whitespace characters: Whitespace separating words should mark the beginning of a new word, thus occurring in front of the first syllable of a new word. This is also valid for new line characters. A syllable followed by a comma should not be broken apart with a sync (both the syllable and the comma should be before the sync). For a more accurate description of the tempo of a musical piece this frame might be used. After the header follows one byte describing which time stamp format should be used. Then follows one or more tempo codes. Each tempo code consists of one tempo part and one time part. The tempo is in BPM described with one or two bytes. If the first byte has the value $FF, one more byte follows, which is added to the first giving a range from 2 - 510 BPM, since $00 and $01 is reserved. $00 is used to describe a beat-free time period, which is not the same as a music-free time period. $01 is used to indicate one single beat-stroke followed by a beat-free period. The tempo descriptor is followed by a time stamp. Every time the tempo in the music changes, a tempo descriptor may indicate this for the player. All tempo descriptors should be sorted in chronological order. The first beat-stroke in a time-period is at the same time as the beat description occurs. There may only be one "SYTC" frame in each tag. The text information frames are the most important frames, containing information like artist, album and more. There may only be one text information frame of its kind in an tag. If the textstring is followed by a termination ($00 (00)) all the following information should be ignored and not be displayed. All text frame identifiers begin with "T". Only text frame identifiers begin with "T", with the exception of the "TXXX" frame. The 'Album/Movie/Show title' frame is intended for the title of the recording(/source of sound) which the audio in the file is taken from. The 'BPM' frame contains the number of beats per minute in the mainpart of the audio. The BPM is an integer and represented as a numerical string. The 'Composer(s)' frame is intended for the name of the composer(s). They are seperated with the "/" character. The 'Content type', which previously was stored as a one byte numeric value only, is now a numeric string. You may use one or several of the types as ID3v1.1 did or, since the category list would be impossible to maintain with accurate and up to date categories, define your own. References to the ID3v1 genres can be made by, as first byte, enter "(" followed by a number from the genres list (appendix A) and ended with a ")" character. This is optionally followed by a refinement, e.g. "(21)" or "(4)Eurodisco". Several references can be made in the same frame, e.g. "(51)(39)". If the refinement should begin with a "(" character it should be replaced with "((", e.g. "((I can figure out any genre)" or "(55)((I think...)". The following new content types is defined in ID3v2 and is implemented in the same way as the numerig content types, e.g. "(RX)". The 'Copyright message' frame, which must begin with a year and a space character (making five characters), is intended for the copyright holder of the original sound, not the audio file itself. The absence of this frame means only that the copyright information is unavailable or has been removed, and must not be interpreted to mean that the sound is public domain. Every time this field is displayed the field must be preceded with "Copyright © ". The 'Date' frame is a numeric string in the DDMM format containing the date for the recording. This field is always four characters long. The 'Encoding time' frame contains a timestamp describing when the audio was encoded. Timestamp format is described in the ID3v2 structure document [ID3v2-strct]. The 'Playlist delay' defines the numbers of milliseconds of silence between every song in a playlist. The player should use the "ETC" frame, if present, to skip initial silence and silence at the end of the audio to match the 'Playlist delay' time. The time is represented as a numeric string. The 'Original release time' frame contains a timestamp describing when the original recording of the audio was released. Timestamp format is described in the ID3v2 structure document [ID3v2-strct]. The 'Recording time' frame contains a timestamp describing when the audio was recorded. Timestamp format is described in the ID3v2 structure document [ID3v2-strct]. The 'Release time' frame contains a timestamp describing when the audio was first released. Timestamp format is described in the ID3v2 structure document [ID3v2-strct]. The 'Tagging time' frame contains a timestamp describing then the audio was tagged. Timestamp format is described in the ID3v2 structure document [ID3v2-strct]. The 'Encoded by' frame contains the name of the person or organisation that encoded the audio file. This field may contain a copyright message, if the audio file also is copyrighted by the encoder. The 'Lyricist(s)/Text writer(s)' frame is intended for the writer(s) of the text or lyrics in the recording. They are seperated with the "/" character. The 'File type' frame indicates which type of audio this tag defines. The following type and refinements are defined: MPG MPEG Audio /1 MPEG 1/2 layer I /2 MPEG 1/2 layer II /3 MPEG 1/2 layer III /2.5 MPEG 2.5 /AAC Advanced audio compression VQF Transform-domain Weighted Interleave Vector Quantization PCM Pulse Code Modulated audio but other types may be used, not for these types though. This is used in a similar way to the predefined types in the "TMED" frame, but without parentheses. If this frame is not present audio type is assumed to be "MPG". The 'Time' frame is a numeric string in the HHMM format containing the time for the recording. This field is always four characters long. The 'Involved people list' is very similar to the musician credits list, but maps between functions, like producer, and names. The 'Content group description' frame is used if the sound belongs to a larger category of sounds/music. For example, classical music is often sorted in different musical sections (e.g. "Piano Concerto", "Weather - Hurricane"). The 'Title/Songname/Content description' frame is the actual name of the piece (e.g. "Adagio", "Hurricane Donna"). The 'Subtitle/Description refinement' frame is used for information directly related to the contents title (e.g. "Op. 16" or "Performed live at Wembley"). The 'Initial key' frame contains the musical key in which the sound starts. It is represented as a string with a maximum length of three characters. The ground keys are represented with "A","B","C","D","E", "F" and "G" and halfkeys represented with "b" and "#". Minor is represented as "m". Example "Cbm". Off key is represented with an "o" only. The 'Language(s)' frame should contain the languages of the text or lyrics spoken or sung in the audio. The language is represented with three characters according to ISO-639-2. If more than one language is used in the text their language codes should follow according to their usage. The 'Length' frame contains the length of the audiofile in milliseconds, represented as a numeric string. The 'Musician credits list' is intended as a mapping between instruments and the musician that played it. Every odd field is an instrument and every even is an artist or a comma delimited list of artists. The 'Media type' frame describes from which media the sound originated. This may be a text string or a reference to the predefined media types found in the list below. References are made within "(" and ")" and are optionally followed by a text refinement, e.g. "(MC) with four channels". If a text refinement should begin with a "(" character it should be replaced with "((" in the same way as in the "TCO" frame. Predefined refinements is appended after the media type, e.g. "(CD/A)" or "(VID/PAL/VHS)". The 'Mood' frame is intended to reflect the mood of the audio with a few keywords, e.g. "Romantic" or "Sad". The 'Original album/movie/show title' frame is intended for the title of the original recording (or source of sound), if for example the music in the file should be a cover of a previously released song. The 'Original filename' frame contains the preferred filename for the file, since some media doesn't allow the desired length of the filename. The filename is case sensitive and includes its suffix. The 'Original lyricist(s)/text writer(s)' frame is intended for the text writer(s) of the original recording, if for example the music in the file should be a cover of a previously released song. The text writers are seperated with the "/" character. The 'Original artist(s)/performer(s)' frame is intended for the performer(s) of the original recording, if for example the music in the file should be a cover of a previously released song. The performers are seperated with the "/" character. The 'Original release year' frame is intended for the year when the original recording, if for example the music in the file should be a cover of a previously released song, was released. The field is formatted as in the "TYER" frame. The 'File owner/licensee' frame contains the name of the owner or licensee of the file and it's contents. The 'Lead artist(s)/Lead performer(s)/Soloist(s)/Performing group' is used for the main artist(s). They are seperated with the "/" character. The 'Band/Orchestra/Accompaniment' frame is used for additional information about the performers in the recording. The 'Conductor' frame is used for the name of the conductor. The 'Interpreted, remixed, or otherwise modified by' frame contains more information about the people behind a remix and similar interpretations of another existing piece. The 'Part of a set' frame is a numeric string that describes which part of a set the audio came from. This frame is used if the source described in the "TALB" frame is divided into several mediums, e.g. a double CD. The value may be extended with a "/" character and a numeric string containing the total number of parts in the set. E.g. "1/2". The 'Produced notice' frame, in which the string must begin with a year and a space character (making five characters), is intended for the production copyright holder of the original sound, not the audio file itself. The absence of this frame means only that the production copyright information is unavailable or has been removed, and must not be interpreted to mean that the audio is public domain. Every time this field is displayed the field must be preceded with "Produced " (P) " ", where (P) is one character showing a P in a circle. The 'Publisher' frame simply contains the name of the label or publisher. The 'Track number/Position in set' frame is a numeric string containing the order number of the audio-file on its original recording. This may be extended with a "/" character and a numeric string containing the total numer of tracks/elements on the original recording. E.g. "4/9". The 'Recording dates' frame is a intended to be used as complement to the "TYER", "TDAT" and "TIME" frames. E.g. "4th-7th June, 12th June" in combination with the "TYER" frame. The 'Internet radio station name' frame contains the name of the internet radio station from which the audio is streamed. The 'Internet radio station owner' frame contains the name of the owner of the internet radio station from which the audio is streamed. The 'Size' frame contains the size of the audiofile in bytes, excluding the ID3v2 tag, represented as a numeric string. The 'Album sort order' frame defines a string which should be used instead of the album name (TALB) for sorting purposes. E.g. an album named "A Soundtrack" might preferably be sorted as "Soundtrack". The 'Performer sort order' frame defines a string which should be used instead of the performer (TPE2) for sorting purposes. The 'Title sort order' frame defines a string which should be used instead of the title (TIT2) for sorting purposes. The 'ISRC' frame should contain the International Standard Recording Code (ISRC) (12 characters). The 'Software/Hardware and settings used for encoding' frame includes the used audio encoder and its settings when the file was encoded. Hardware refers to hardware encoders, not the computer on which a program was run. The 'Set subtitle' frame is intended for the subtitle of the part of a set this track belongs to. The 'Year' frame is a numeric string with a year of the recording. This frames is always four characters long (until the year 10000). This frame is intended for one-string text information concerning the audiofile in a similar way to the other "T"-frames. The frame body consists of a description of the string, represented as a terminated string, followed by the actual string. There may be more than one "TXXX" frame in each tag, but only one with the same description. This frame's purpose is to be able to identify the audio file in a database that may contain more information relevant to the content. Since standardisation of such a database is beyond this document, all frames begin with a null-terminated string with a URL [URL] containing an email address, or a link to a location where an email address can be found, that belongs to the organisation responsible for this specific database implementation. Questions regarding the database should be sent to the indicated email address. The URL should not be used for the actual database queries. If a $00 is found directly after the 'Frame size' the whole frame should be ignored, and preferably be removed. The 'Owner identifier' is then followed by the actual identifier, which may be up to 64 bytes. There may be more than one "UFI" frame in a tag, but only one with the same 'Owner identifier'. This frame contains a brief description of the terms of use and ownership of the file. More detailed information concerning the legal terms might be available through the "WCOP" frame. Newlines are allowed in the text. There may only be one "USER" frame in a tag. This frame contains the lyrics of the song or a text transcription of other vocal activities. The head includes an encoding descriptor and a content descriptor. The body consists of the actual text. The 'Content descriptor' is a terminated string. If no descriptor is entered, 'Content descriptor' is $00 (00) only. Newline characters are allowed in the text. There may be more than one 'Unsynchronised lyrics/text transcription' frame in each tag, but only one with the same language and content descriptor. With these frames dynamic data such as webpages with touring information, price information or plain ordinary news can be added to the tag. There may only be one URL link frame of its kind in an tag, except when stated otherwise in the frame description. If the textstring is followed by a termination ($00 (00)) all the following information should be ignored and not be displayed. All URL link frame identifiers begins with "W". Only URL link frame identifiers begins with "W". The 'Commercial information' frame is a URL pointing at a webpage with information such as where the album can be bought. There may be more than one "WCOM" frame in a tag, but not with the same content. The 'Copyright/Legal information' frame is a URL pointing at a webpage where the terms of use and ownership of the file is described. The 'Official audio file webpage' frame is a URL pointing at a file specific webpage. The 'Official artist/performer webpage' frame is a URL pointing at the artists official webpage. There may be more than one "WOAR" frame in a tag if the audio contains more than one performer, but not with the same content. The 'Official audio source webpage' frame is a URL pointing at the official webpage for the source of the audio file, e.g. a movie. The 'Official internet radio station homepage' contains a URL pointing at the homepage of the internet radio station. The 'Payment' frame is a URL pointing at a webpage that will handle the process of paying for this file. The 'Publishers official webpage' frame is a URL pointing at the official wepage for the publisher. This frame is intended for URL links concerning the audiofile in a similar way to the other "W"-frames. The frame body consists of a description of the string, represented as a terminated string, followed by the actual URL. The URL is always encoded with ISO-8859-1. There may be more than one "WXXX" frame in each tag, but only one with the same description.