[Matroska-devel] Mapping the tag leftovers

Steve Lhomme steve.lhomme at free.fr
Sat Sep 18 19:31:13 CEST 2004

Age Bosma a écrit :

> 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.

In Segment > Tracks > TrackEntry > TrackType+CodecID+CodecName

>   Length of the audio file in milliseconds.

This is the duration of the chapter the tag targets. Otherwise the 
Segment duration :
Segment > Info > Duration

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

In Segment > Tracks > TrackEntry > TrackOffset although it's probably 
not used yet

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

The size of the Segment

>   Allows synchronisation with key events in the audio.

No idea of what it is

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

Not really MPEG related but that's the MetaSeek and Cue entries :
Segment > SeekHead
Segment > Cues

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

You should use chapters + BPM tag for that.

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

We don't have that.

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


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

You can put all kind of shit with new EBML elements...

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

Somehow it's Segment > Tracks > TrackEntry > MaxCache

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

There is EBML encryption, but that's somehow different. There is no 
encryption only the coded data (so far).

>   Used to link information from another ID3v2 tag.

We don't have that

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

Dunno exactly what it means...

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


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

That would be the Segment > MetaSeek

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

That would be Segment > Cues

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

That's somehow the ReplayGain, with a custom setting. Maybe we should 
add a GAIN tag that would be subjective (as opposed to ReplayGain).

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

We don't have that

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


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


> APE:
> - FILE
>   File location.

Maybe that's Segment > Info > SegmentFilename

>   Indexes for quick access.

MetaSeek and Cues

>   Characteristic part of piece for intro playing.

That could be a chapter with a special name, or a new "managed" chapter 
type to allow this special functionality.

> - IDPI
>   Dots Per Inch. Stores dots per inch setting of the digitizer used to
>   produce the file, such as "300."

No thanx. But we have a corresponding physical size for video frames :
Segment > Tracks > TrackEntry > Video > DisplayUnit

> - 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."

Codec specific.

> - 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."

Segment > Tracks > TrackEntry > Video > PixelCropBottom + PixelCropTop + 
  PixelCropLeft + PixelCropRight

> - IDIM
>   Dimensions. Specifies the size of the original subject of the file.
>   For example, "8.5 in h, 11 in w."


> - ICNT*
>   Country

Depends to what it applies. We have countries for tracks and chapters.

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