Re: [gentoo-user] Questions about recording webcam+mic on netbook

[Walter Dnes]

On Sat, Oct 06, 2012 at 07:48:50AM -0400, Michael Mol wrote

> When I last used guvcview, it muxed both audio and video into an
> appropriate container format for me, but it was all very configurable.
> I do recall I went with MJPEG for a video codec.[1]
>
> I realize you're not fond of GNOME, but guvcview doesn't require
> pulling in all of gnome. Though looking at it now, it may require
> pulseaudio.
>
> I haven't tried luvcview, sorry.
>
> [1] This video was recorded with guvcview, and then uploaded as-is.
> http://www.youtube.com/watch?v=kul0eGILCI4

  I eventually did it "the unix way", stringing together a couple of
programs.  The following is one long line...

ffmpeg -y -f alsa -i plughw:0,0 -f video4linux2 -i /dev/video0 -f avi -vcodec mpeg4 /dev/stdout | tee output.avi | mplayer -cache 32 -


ffmpeg encodes the streams from webcam+microphone, and spits it out to
stdout, which is piped to the "tee" program.  "tee" sends out 2
duplicate streams...
1) to diskfile output.avi
2) to stdout, which is piped to mplayer, which displays a copy of the
stream onscreen

  There's approximately a 1-second lag, but that's OK.  The terminal
from which the command is launched produces warnings each time the cache
is emptied, but it works.  Remember that this is an early Intel Atom Z520
which is rather weak.  There is finally an open source kernel driver for
the Intel/Poulsbo GPU, but it has no acceleration.  The fact that it
works acceptably is a minor miracle.  The only mplayer video option that
works properly is the barebones "x11" option.  All others except the
"fbdev2" either produce no video, or output in "seconds per frame",
rather than "frames per second" <G>.  fbdev2 may be a bit faster than
x11, but it has its own issues...

1) Since it bangs away directly at the framebuffer, you need higher
permissions; i.e. either root or setuid.

2) It slaps the output in the upper left corner of the screen,
overwriting X, because it writes directly to framebuffer.

-- 
Walter Dnes <waltdnes@××××××××.org>
I don't run "desktop environments"; I run useful applications