GStreamer

Introduction

The gstreamer0.10-plugins-bad package in Debian recently added Video4Linux2 capture support (cf. bug #379867).

Documentation

1. Gstreamer project
2. FAQ
3. Documentation
4. Core plugins
5. FFMpeg plugins
6. Base plugins
7. Good plugins
8. Bad plugins
9. Ugly plugins
10. man gst-launch

Webcam commands

gst-launch-0.10 v4l2src use-fixed-fps=false ! video/x-raw-yuv,format=\(fourcc\)UYVY,width=320,height=240 \
! ffmpegcolorspace ! ximagesink

gst-launch-0.10 v4lsrc autoprobe-fps=false device=/dev/video0 ! "video/x-raw-yuv, width=160, height=120, \
framerate=10, format=(fourcc)I420" ! xvimagesink 

TV capture commands

Record to ogg theora

gst-launch-0.10 oggmux name=mux ! filesink location=test0.ogg v4l2src device=/dev/video2 ! \  
video/x-raw-yuv,width=640,height=480,framerate=\(fraction\)30000/1001 ! ffmpegcolorspace ! \
theoraenc ! queue ! mux. alsasrc device=hw:2,0 ! audio/x-raw-int,channels=2,rate=32000,depth=16 ! \
audioconvert ! vorbisenc ! mux.

The files will play in mplayer, using the codec Theora or [raw] RAW Uncompressed Video. I was unable to get sound output, though mplayer claimed there was sound -- the video is good quality:

VIDEO:  [theo]  640x480  24bpp  29.970 fps    0.0 kbps ( 0.0 kbyte/s)
Selected video codec: [theora] vfm: theora (Theora (free, reworked VP3))
AUDIO: 32000 Hz, 2 ch, s16le, 112.0 kbit/10.94% (ratio: 14000->128000)
Selected audio codec: [ffvorbis] afm: ffmpeg (FFmpeg Vorbis decoder)

Note the required workaround to get sound on a saa7134 card, which is set at 32000Hz (cf. bug).

Record to mpeg4

Or mpeg4 with an avi container (Debian has disabled ffmpeg encoders, so use example above):

gst-launch-0.10 avimux name=mux ! filesink location=test0.avi v4l2src device=/dev/video2 ! \
video/x-raw-yuv,width=640,height=480,framerate=\(fraction\)30000/1001 ! ffmpegcolorspace ! \ 
ffenc_mpeg4 ! queue ! mux. alsasrc device=hw:2,0 ! audio/x-raw-int,channels=2,rate=32000,depth=16 ! \ 
audioconvert ! lame ! mux.

Playing the file back in mplayer, I was unable to get sound output, though mplayer claimed there was sound -- the video is good quality:

VIDEO:  [theo]  640x480  24bpp  29.970 fps    0.0 kbps ( 0.0 kbyte/s)
Selected video codec: [theora] vfm: theora (Theora (free, reworked VP3))
AUDIO: 32000 Hz, 2 ch, s16le, 112.0 kbit/10.94% (ratio: 14000->128000)
Selected audio codec: [ffvorbis] afm: ffmpeg (FFmpeg Vorbis decoder)

=Record to raw video

If you don't care for sound, this simple version works for uncompressed video:

gst-launch-0.10 v4l2src device=/dev/video5 ! video/x-raw-yuv,width=640,height=480 ! avimux ! \
filesink location=test0.avi

tcprobe says this video-only file uses the I420 codec and gives the framerate as correct NTSC:

$ tcprobe -i test1.avi
[tcprobe] RIFF data, AVI video
[avilib] V: 29.970 fps, codec=I420, frames=315, width=640, height=480
[tcprobe] summary for test1.avi, (*) = not default, 0 = not detected
import frame size: -g 640x480 [720x576] (*)
       frame rate: -f 29.970 [25.000] frc=4 (*)
   no audio track: use "null" import module for audio
           length: 315 frames, frame_time=33 msec, duration=0:00:10.510

The files will play in mplayer, using the codec [raw] RAW Uncompressed Video.

Converting formats

To convert the files to matlab (didn't work for me):

mencoder test0.avi -ovc raw -vf format=bgr24 -o test0m.avi -ffourcc none 

For details, see gst-launch and google; the plugins in particular are poorly documented so far.