Hi Benjamin,
First off, thank you very much for your suggestions. Every little optimization counts on
this platform, and we need all of the help we can get.
Second, if you're in the Boston area on Friday, the OpenVideoChat team is coming down
from Rochester and we'll be at the GNOME Python Hackfest[0] at the OLPC offices, and
then BarCampBoston[1] on Saturday.
We're hoping to get as many OLPC/Sugar/Telepathy/Gstreamer/Theora people there as
possible.
Cheers,
luke
[0]:
http://live.gnome.org/Hackfests/Python2010
[1]:
http://www.barcampboston.org
----- "Benjamin M. Schwartz" <bmschwar(a)fas.harvard.edu> wrote:
You seem to be interested in codec speed optimizations. I'm a
Theora/Sugar/OLPC dev, so I'd like to help with that. I've heard
your
pipelines look like
10:07 lmacken> GST_INPIPE = "udpsrc ! theoradec !
ffmpegcolorspace !
ximagesink"
10:07 lmacken> GST_OUTPIPE_BASE = "v4l2src ! theoraenc
bitrate=50
speed-level=2
keyframe-force=1 ! udpsink host=%s"
You would do better with
GST_INPIPE = "udpsrc ! theoradec ! ffmpegcolorspace ! xvimagesink"
Using xvimagesink instead of ximagesink engages the graphics
processor's
output acceleration.
GST_OUTPIPE_BASE = "v4l2src !
video/x-raw-yuv,width=320,height=240,framerate=15/1,format="(fourcc)I420"
! theoraenc bitrate=50 speed-level=2 ! udpsink host=%s"
I've added gstreamer "caps" (capabilities) after v4l2src to reduce
the
video resolution produced by the camera. Encoding 640x480 at 15 fps
is
unlikely to be viable even on an XO-1.5. I've also removed
"keyframe-force", since it's likely to have a major negative impact
on
image quality at fixed bitrate.
Using these pipelines will probably require you to upgrade to OS119
due to
bug #10106.
I don't recommend that you attempt grayscale encoding. The color
data
(chroma planes) require very little bandwidth and CPU time. You'll
only
make things slower by trying to filter it out. To make things faster
you'd have to modify the Theora encoder, and then you'd have grayscale
output.
--Ben
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