[Matroska-devel] Re: Status Quo of new features

Paul Bryson paul at msn.com
Mon Dec 27 12:08:26 CET 2004


"Steve Lhomme" wrote...
>> - DV ( camcorder, lossy compression ) support, type 1 ( a +v = 1 stream ) 
>> and 2 ( a , a+v : 2 streams ); mainly some AVI parsing and defining how 
>> to handle the embedded audio stream ( AVI has to repeat the PCM WAV audio 
>> stream --> ENORMOUS overhead )
>
> As I've worked on MTX a bit, I think I could be able to add DV support 
> too. Actually we would store the audio and video in separate tracks, not 
> using the complex type, since the DV format is known we can demux it.

DV is strange because if you encode only video to DV, it still uses the same 
space for the PCM, but it marks it as no audio.  It would be possible to 
store just the video frame data, but the splitter would need to recreate 
Video + Null Audio stream on playback for anything to be able to use it.  If 
I recall correctly, it basically uses something like JPEG images for the 
video, very similar to MJPEG video.  I know we all have visions of using DV 
video with Wavpack audio without having to store all of that silly PCM 
overhead.

http://www.adamwilt.com/DV-FAQ-tech.html
"DV video information is carried in a nominal 25 megabit per second 
(Mbits/sec) data stream. Once you add in audio, subcode (including 
timecode), Insert and Track Information (ITI), and error correction, the 
total data stream comes to about 29 Mbits/sec or 3.6 MBytes/sec."

That means you could shave off about 14% overhead for video only stuff by 
storing only the video frames.  Or about 9% for video + audio.  Impressive, 
but sounds like a good deal of work.


Atamido 






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