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by jmillikin 5957 days ago
It's been a while since I looked at the metadata standards, but it's my memory that there are two: one that is "deprecated", supports only a few tags, and is supported by libraries,, and the "new" format you linked to, which is the "way forward" but so far completely unsupported by anything.

The specific problems I remember are that the ReplayGain tag contents are unspecified (decimal, like Vorbis/FLAC? IEEE754 half, single, double in some endianness?), there's no support for cover art, and the "examples" are all broken links. In my opinion, FLAC has the best metadata support -- Vorbis is close, but its cover art support is a catastrophe.
1 comments
yuvi 5957 days ago
No clue what the depreciated version might be, as far as I know what I linked to hasn't changed since sometime around 2005 (which would explain any broken links.)

Cover art wasn't specifically defined in mkv I think, but it became standard to do an attachment named cover.jpg for it.

The spec on ReplayGain seems pretty clear to me: it's the 16-bit binary format defined at http://replaygain.hydrogenaudio.org/rg_data_format.html which is two links away from the mkv spec.

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jmillikin 5957 days ago
The "original" 9-bit fixed-point encoding isn't widely used; most formats use a 32- or 64-bit float, or the number encoded as a string. One of the Matroska developers posted on the HydrogenAudio forums[1] saying they use a 32-bit float, but the spec he quotes later[2] is different than what's on the actual Matroska site.

Do you know if the cover.jpg standard is documented anywhere? Searching for "matroska cover.jpg" just yields a bunch of bittorrent sites.

[1] http://www.hydrogenaudio.org/forums/index.php?showtopic=7294...

[2] http://www.hydrogenaudio.org/forums/index.php?showtopic=7294...

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yuvi 5957 days ago
I think cover.jpg came from doom9 [1]

I guess robux4 was talking about the old system, which I honestly didn't know existed before you brought it up. If the new system doesn't use the 16 bit format then yeah, it isn't well specified.

[1] http://forum.doom9.org/showthread.php?p=388815#post388815

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