GStreamer

GStreamer is a multimedia processing library which front end applications can leverage in order to provide a wide variety of functions such as audio and video playback, streaming, non-linear video editing and V4L2 capture support.

Documentation

• Gstreamer project
• FAQ
• Documentation
  • Core plugins
  • FFMpeg plugins
  • Base plugins
  • Good plugins
  • Bad plugins
  • Ugly plugins
• 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 

V4L TV capture commands

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

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. Note the required workaround to get sound on a saa7134 card, which is set at 32000Hz (cf. bug). However, I was still 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 mpeg4

Or mpeg4 with an avi container (Debian has disabled ffmpeg encoders, so install Marillat's package or 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.

I get a file out of this that plays in mplayer, with blocky video and no sound. Avidemux cannot open the file.

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.

External Link

• GStreamer project page
• GStreamer Wikipedia page