[Matroska-devel] Re: Mapping the tag leftovers

Paul Bryson paul at msn.com
Fri Sep 17 22:13:25 CEST 2004

"Age Bosma" wrote...
> ID3:
>   Indicates, by defined codes, which type of audio this tag defines;
>   e.g. "MPEG Audio" (default), "MPEG 1/2 layer III", "Advanced Audio
>   Compression", etc.

Should be apparent as part of the CodecID.

>   Length of the audio file in milliseconds.

If the Matroska file contains only one stream, then you could just use the 
Duration element.

>   Defines the numbers of milliseconds of silence that should be inserted
>   before this audio.

I don't think there is a comparable item in Matroska

> - SIZE
>   Contains the size of the audiofile in bytes, excluding the ID3v2 tag.

If the Matroska file contains only one stream, then you could just use the 
Duration element and multiply it by the BPS tag.  That should give you a 
relatively accurate size of the stream excluding container overhead.

>   Allows synchronisation with key events in the audio.

I don't understand what this is for.  Maybe it would be like Chapters?

>   MPEG location lookup table to increase performance and accuracy of
>   jumps within an audio file.

That sounds like the Cues that are used to indicate seek points.

>   Synchronised tempo codes for a more accurate description of the tempo
>   of a musical piece.

Nothing that I know of.  Although, you could make another track that just 
has data for tempo stuff.  Make a Tempo Codec.

>   Subjective alignment frame to predefine an equalisation curve within
>   the audio file.

Possibly the  REPLAYGAIN info in the tags?

>   Subjective frame that allows you to adjust echoes of different kinds.

Nothing I can think of.

>   In this frame any type of file can be encapsulated.

We have  AttachedFile within Matroska.

>   Buffer size recommended by the server using this frame (in case of
>   streaming).

Nothing I can think of.

>   Indicates if the actual audio stream is encrypted, and by whom.

ContentEncryption within Matroska has all sorts of encryption options.

>   Used to link information from another ID3v2 tag.

None.  Although you can nest tags in Matroska which makes this info a bit 

>   Delivers information to the listener of how far into the audio stream
>   he picked up.

If/when Matroska is ever set up for streaming, you could tell how far in you 
are from the timecodes being sent.

>   To identify with which method a frame has been encrypted.

ContentEncAlgo within ContentEncryption contains this info.

>   This frame indicates where other tags in a file/stream can be found.

The  SeekHead in Matroska contains info about where all other major elements 
are stored.

>   Makes seeking in audio files with variable bit rates easier using an
>   audio seek point index.

This is Cues again.

>   Used to indicate how much the volume on each channel has to be
>   increased/decreased while the file is played.

Not sure, possibly  REPLAYGAIN again.

>   Subjective alignment frame to predefine an equalisation curve within
>   the audio file.

Not sure, possibly  REPLAYGAIN again.

>   Enables grouping of otherwise unrelated frames; e.g. when some frames
>   are to be signed.

This is possible within the constraints of a Cluster in Matroska, but there 
isn't a way to specify a large arbitrary range for signing.

>   Enables a group of frames, grouped with GROUPINGREG, to be signed.

SignatureSlot witin Matroska

> APE:
> - FILE
>   File location.

What is this for?

>   Indexes for quick access.

Cues again.

>   Characteristic part of piece for intro playing.

You could mark an area as an intro by using Chapters, but there is nothing 


All of the RIFF tags were at one point in the Matroska tags list, but were 
slowly removed as they were recognized as a very niche market.  If there is 
a need to store them, then people will undoubtedly make a custom tag, but 
adding them to the specs could definately fall into the category of bloat. 
(Somebody might someday use this tag)  One that might actually get used is 
the ICRP tag, and if there were one, the resized tag.

> - IDPI
>   Dots Per Inch. Stores dots per inch setting of the digitizer used to
>   produce the file, such as "300."
> - ILGT
>   Lightness. Describes the changes in lightness settings on the
>   digitizer required to produce the file. Note that the format of this
>   information depends on hardware used.
> - IPLT
>   Palette Setting. Specifies the number of colors requested when
>   digitizing an image, such as "256."
> - ISHP
>   Sharpness. Identifies the changes in sharpness for the digitizer
>   required to produce the file (the format depends on the hardware
>   used).
> - ICRP
>   Cropped. Describes whether an image has been cropped and, if so, how
>   it was cropped. For example, "lower right corner."
> - IDIM
>   Dimensions. Specifies the size of the original subject of the file.
>   For example, "8.5 in h, 11 in w."
> - ICNT*
>   Country


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