[FFmpeg-devel] Feature Request for ffmpeg

christian chr1123443
Mon Jun 1 00:51:33 CEST 2009


I hope, this is the correct mailing list for a feature request.

This is a request for adding the rtvc1 video codec to ffmpeg. rtvc1 is also calles RTVideo and its a modified version of VC-1.
This codec is used in Windows Live Messenger Webcam Conversations. The dll file in the Messenger Directory is "rtmpltfm.dll" the description is "Microsoft Real Time Media Stack". Theres a second dll in the directory called "wmv9vcm.dll" the description of this file is Windows Media Video 9 VCM.

This document on the msdn Network descripes the payload Types and the headers of the I,P,B and SP frames of the video. http://download.microsoft.com/download/1/6/F/16F4E321-AA6B-4FA3-8AD3-E94C895A3C97/[MS-RTVPF].PDF

I Recorded a webcam session between me and my friend with wireshark for testing purposes.Then i saved the payload within Wireshark. Statistics -> RTP -> Show all Streams -> Analyze -> Save Payload 
I only saved the payload of the forward direction. Its not useful to feed ffplay with a stream from both directions :)

I tryed to play such stream file with ffmpeg with some useful results.
FFplay is able to play the first packet of all I-Frames.It uses the ffvc1codec.If i play the file, ffplay shows me the first upper part of the video. The rest is only a mixture of colors and pixels.
The next packets of the I frames are starting with this header "cc000000" the last packet of an I frame starts with "dc000000". If i remove all "cc000000" and "dc000000" from all packets using a hex editor, ffplay is able to play the whole I frame and i get a full video. But the framerate is to high and there are missing frames. ffplay is unable to play the P,B and SP frames. It only can play the I frames.

Perhaps someone could/want to add this codec to ffmpeg.

I hope i gave enough information about the codec and the headers. I?ll keep trying to play the file. I'am playing around with the hex editor. If i find anything new, i'll post it.

Greetings Chris

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