Transcoding from video capture (and streaming) is borked

[Lloyd]

This problem has been noticed in several posts, and I thought I would summarise the problem, the cause and the solution so that someone with the time and the inclination can implement the solution.

The symptoms are that people with nVidia VIVO cards get streaming video that can best be described as 'green'. If VLC displays the data directly to the screen without transcoding it, no problem is observed.

The input format is UYVY and the dshow-chroma setting doesn't seem to change the way this is dealt with.

By capturing the stream to a raw file (at 1fps) I was able get sample data without filling up any disks. I then threw a couple of possible decoders at it. The first one produced the same green as VLC, and the second one worked correctly.

The broken code is loosely based on the example code for UYVY at http://www.efg2.com/Lab/Graphics/Colors/YUV.htm. The code that works is in the NetPBM package.

You can fetch the sample data, broken code, working code and the resulting pictures from

http://www.must-have-coffee.gen.nz/vlc/ ... stream.bz2
http://www.must-have-coffee.gen.nz/vlc/broken.c
http://www.must-have-coffee.gen.nz/vlc/broken.jpeg
http://www.must-have-coffee.gen.nz/vlc/works.c
http://www.must-have-coffee.gen.nz/vlc/works.jpeg

Someone now needs to replace the broken code in VLC with the good code from NetPBM. That someone won't be me. Well, I certainly won't be building Windows binaries which are what will be needed for testing.

Cheers,
Lloyd

[Gibalou]

Thanks, for investigating this. This has just been fixed in the development version (and 0.8.1 will contain the fix).

[D.C]

Lloyd, Thanks for the great job on investigating on the "Green" picture problem.
I just downloaded the latest nightly build (Nov. 15. 2004) and it works great. No more "Green" picture