[Matroska-devel] Lossless audio codecs for video editing

Christian HJ Wiesner chris at matroska.org
Tue Dec 28 22:26:40 CET 2004


Hi,

this email is sent to flac-dev AT xiph DOT org, copied to matroska-devel 
AT lists DOT matroska DOT org, and David Bryant, the author of Wavpack4.

We are about to implement the DV ( Digital Video ) video compression 
standard into matroska, to be able to offer an intelligent alternative 
to AVI for DV handling in editor tools. DV is using a high quality, high 
bitrate lossy video compression similar to MJPEG, so there are no I/P/B 
frames, you can cut the DV AVI wherever you like. The sound is typically 
PCM, and in a type 1 DV AVI the video and audio will form a single 
stream ( like in the DV format itself ). As most AVI editors cant handle 
a stream containing  audio and video, there is also type 2 DV AVI, where 
the PCM audio stream is repeated in a second track, to make it 
accessible. I heard Virtualdub has recently added support for type 1 DV 
AVI, but i couldnt verify this.

Our goal is to allow the use of lossless audio with a single DV video ( 
PCM audio stripped ), to save HDD space during the editing process. MKV 
has perfect support for FLAC since more than a year, and we are about to 
add Wavpack4 support right now.

I was wondering how suitable both are with respect to video editing, 
especially if it comes to sample precise cutting. What is the absolute 
minimal number of samples per frame in a FLAC stream ? Can we change the 
number of samples in the same track ?

Hopefully you understand where my question is coming from, we normally 
cant cut audio streams in between frames during the video editing 
process, but its not given in any case that frame boundaries of the DV 
video stream will match those of the audio stream, and this could lead 
to problems. For this reason we will concentrate on the one lossless 
audio format for the DV editing that will allow us the finest sample 
size, for precise editing.

I know we could try to dig this all up from your docs, but maybe you 
have an idea how we could best use your codecs for this purpose ?

Christian
matroska project admin
http://www.matroska.org



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