[MPlayer-dev-eng] ADPCM Document

[Alex Beregszaszi]

On Sun, Dec 30, 2001 at 10:42:22AM -0700, Mike Melanson wrote:
> On Sun, 30 Dec 2001, Arpi wrote:
> 
> > avi: there are lots of docs flying around on teh net, but most of them are
> > inaccurate, miss important details or has bad information.
> > 
> > asf: m$ released specification of ASF v2.0 format. it'd detailed enough, and
> > is nice, the only problem with it: nobody uses this file format.
> > all products use asf v1.0, which is not documented at all. (and differs from 2.0)
> > (except that rev.eng doc by avifile author i sent you yesterday)
> > 
> > vivo: not documented at all. i did the reverse engineering of file format.
> > anyway, it was very easy. it's like rle-encoded stuff with interleaved
> > audio-video chunks.
> 
> 	I'm thinking I had better revise my assertion on the CRI that "The
> internals of the most common multimedia file formats are well-documented."
> Maybe it should be, "The internals of QT and RM are fairly
> well-documented, but not entirely. Everything else, good luck!" Come to
> think of it, I haven't seen a revision of the QT spec that mentions
> compressed headers (though I haven't looked in awhile). If they still
> don't mention that in the latest document, that would be a good candidate
> for our QT-quirks document.
> 
> 	As an aside, why on earth did Apple feel it necessary to employ
> compressed headers? Honestly, I have some QT trailers that are 50
> megabytes large, but they managed to save a few bytes by compressing a
> header that, at worst, is a few 10s of kilobytes large. It just seems
> negligible by comparison.

Possible ground: zlib compressed header uses crc :)

> 
> --
> 	-Mike Melanson
> 
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