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

["Canek Peláez Valdés" <caneko@gmail.com>]

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