h.264 optimized playback settings?

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1

Hi all,

I was transcoding some avi’s to h.264’s with ffmpeg to play back on the beagleboard with mplayer. Just using the CPU not the DSP decoding and noticed that my h.264’s utilize a lot more of the CPU(90% vs 65%) then if I play back BigBuckBunny, even though my videos are smaller resolution(512x256 vs 640x360) and lower bitrate (600k vs 1500k). This is the command I used to transcode:
/usr/local/bin/ffmpeg -i $try.avi -y -pass 1 -vcodec libx264 -vpre fastfirstpass -b $1 -bt $1 -threads 0 $try.mov
/usr/local/bin/ffmpeg -i $try.avi -y -pass 2 -vcodec libx264 -vpre hq -b $1 -bt $1 -threads 0 $try.mov
All of my videos don’t contain any sound track and I have tested multiple bitrates.

Are there any settings that I need to consider for transcoding that would help playback, and does anyone know the settings used for the BigBuckBunny video and why it plays back at less utilization?

Thanks

Kevin

2

Kevin Holland wrote:

Hi all,

I was transcoding some avi's to h.264's with ffmpeg to play back on the
beagleboard with mplayer. Just using the CPU not the DSP decoding and
noticed that my h.264's utilize a lot more of the CPU(90% vs 65%) then
if I play back BigBuckBunny, even though my videos are smaller
resolution(512x256 vs 640x360) and lower bitrate (600k vs 1500k). This
is the command I used to transcode:
/usr/local/bin/ffmpeg -i $try.avi -y -pass 1 -vcodec libx264 -vpre
fastfirstpass -b $1 -bt $1 -threads 0 $try.mov
/usr/local/bin/ffmpeg -i $try.avi -y -pass 2 -vcodec libx264 -vpre hq -b
$1 -bt $1 -threads 0 $try.mov
All of my videos don't contain any sound track and I have tested
multiple bitrates.

Are there any settings that I need to consider for transcoding that
would help playback, and does anyone know the settings used for the
BigBuckBunny video and why it plays back at less utilization?

you might consider using MPEG4 instead of H264 for these resolutions.

3

Try adding -coder 0, this will use CAVLC entropy encoding instead of
CABAC.

CABAC offers some increased compression but is horrible to decode in
terms of performance, also I think that CAVLC in ffmpeg is assembler
optimized.

4

arte <carl.hakenas@gmail.com> writes:

Try adding -coder 0, this will use CAVLC entropy encoding instead of
CABAC.

CABAC offers some increased compression but is horrible to decode in
terms of performance, also I think that CAVLC in ffmpeg is assembler
optimized.

There is no ARM assembler for CABAC or CAVLC in FFmpeg (yet). You're
correct, of course, that CAVLC is faster to decode.

5

There is no ARM assembler for CABAC or CAVLC in FFmpeg (yet).

Aha OK. I mixed it up with the free NEON openmax stuff.
Wonder why nobody has adopted them for ffmpeg?

6

arte <carl.hakenas@gmail.com> writes:

There is no ARM assembler for CABAC or CAVLC in FFmpeg (yet).

Aha OK. I mixed it up with the free NEON openmax stuff.
Wonder why nobody has adopted them for ffmpeg?

Maybe because openmax is a horrible mess.