Re: [gentoo-user] [OT} GStreamer: How to view AND record a stream coming from an USB Webcam

[meino.cramer@gmx.de]

Canek Peláez Valdés <caneko@gmail.com> [14-06-16 04:33]:
> On Sun, Jun 15, 2014 at 1:04 PM, Canek Peláez Valdés <caneko@gmail.com> wrote:
> > On Sun, Jun 15, 2014 at 12:54 PM,  <meino.cramer@gmx.de> wrote:
> >> Hi,
> >>
> >> After unsuccessfully trying vlc with a Logitech C920 HD Pro Webcam
> >> (over 2 seconds delay between audio and video). I played around
> >> with gstreamer and from bits and pieces from the web I build
> >> this line:
> >>
> >>     gst-launch-1.0 v4l2src device=/dev/video1 ! video/x-h264,width=1920,height=1080,framerate=30/1 ! \
> >>     h264parse ! muxout. alsasrc device="hw:3,0" ! queue ! audioconvert ! lamemp3enc ! \
> >>     muxout. matroskamux name=muxout streamable=true ! filesink location=c920.mp4
> >>
> >> which records a Full HD video with audio to my harddisc. The delay is
> >> minimal and the sync between audio and video is good.
> >>
> >> But there is one disadvantage:
> >> I cannot see what I am recording and I cannot watch the webcams stream
> >> before I fire up the script because otherwise the device would be "already
> >> in use" (I dont like scripts, which simply kill other applications when
> >> called).
> >>
> >> Any ideas or hints how to manage that?
> >
> > Use the tee element. I'm in a hurry, so I cannot test a pipeline right
> > now, but I will try later. Meanwhile, just try to put a queue element
> > after each path of the tee.
> >
> > gst-inspect-1.0 tee
> 
> OK, it took me a bit of an effort, but this is my pipeline:
> 
> gst-launch-1.0 v4l2src norm=NTSC device=/dev/video1 ! queue !
> deinterlace mode=1 ! videorate !
> video/x-raw,format=YV12,width=720,height=480,framerate=30000/1001 !
> tee name=t t. ! queue ! videoconvert ! mpeg2enc ! avimux ! filesink
> location=file.avi t. ! queue ! videoconvert ! autovideosink
> 
> My hardware is much more limited (analog RGB), so resolution and
> famerate are accordingly lower. This captures to an AVI file encoded
> to MPEG2 the video signal, and at the same time it opens a window to
> show the stream.
> 
> It should not be that much of a problem to modify it to your needs;
> just notice that I didn't capture audio.
> 
> Regards.
> -- 
> Canek Peláez Valdés
> Profesor de asignatura, Facultad de Ciencias
> Universidad Nacional Autónoma de México
> 

Hi Canek,

Thanks a lot for your effort!!! 8)

Is there any documentation out there about this "How to build 
a pipeline with gst-launch", which you would recommend to read?

I will see how I can map your example to my code I have already, which 
handles audio and video...

Best regards,
mcc