[PD] pix_film + incrementing frame number = blurring

Olivier Heinry olivier.heinry at free.fr
Tue Jul 3 00:14:02 CEST 2012

Le 02/07/2012 23:19, Iain Mott a écrit :
> Forgot to mention i'm using Ubuntu 11.10 and the video files are 30 fps
> with the codec H.264 / AVC
What are your encoding settings? I always use a GOP size of 1 with h264, 
otherwise you might encounter temporal interpolation artefacts at 
playtime. Have a look at the Blender 3D snapshot at the bottom of 

There is also a very nice H264 encoder called h264enc which might help you

If you'd rather use a gui, try 

Here are a command line which has proven useful:

  ffmpeg -an -y -i DSCN0716.MOV -r 25 -s 960x540 -f avi -vcodec libx264 -b:v 50000k -g 1 -keyint_min 25 -sc_threshold 40 -i_qfactor 0.71 -b_strategy 1 /bigfiles/DSCN0176.mp4

key parameter is the -g option , set it to one so to have a keyframe 
every frame, hence no interpolation at all. If you're rether the 
datamosh guy, just set very very high ;-) such as this one courtesy BenJah :

ffmpeg -i input_video.mov -g 250 -sc_threshold 1000000000 -vcodec libxvid output_video.mp4

All these are compiled on the French-speaking Labomédia wiki:


> Also, while sending an "auto 1" message to pix_film gives smooth
> playback, the file plays perhaps 30% slow. This doesn't seem to be a CPU
> issue as the cpu is running between 20 and 30% while playing the file.

Auto 1 doesnt always detect the right framerate as I have experienced. 
Pix_movie is more reliable.


> Iain
> On Mon, 2012-07-02 at 17:14 -0300, Iain Mott wrote:
>> Hi list,
>> I have a patch that syncs multi-channel audio with video by passing
>> frame numbers to pix_film. These frame numbers are generated by the
>> audio playback. With HD video however and scenes including smooth
>> movements, the image becomes a little jittery and a bit blurred. I tried
>> completely disabling the audio but it made no effect. When audio is
>> enabled and I run the pix_film with an "auto 1" message, playback is
>> excellent.
>> I'll experiment now to see if lip-sync can be maintained without propper
>> frame-sync, since my clips have at maximum 3min duration.
>> I'm wondering though if anyone else had come across this blurring?
>> I'm using by the way, a heavily butchered version of Hans-Christoph's
>> framesync (and an old version of it). However, even if don't use the
>> framesync patches and pass a frame count generated with metro and a
>> counter at the correct rate of 30fps - the blurring still happens.
>> Suggestions most welcome!
>> Cheers,
>> Iain
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olivier at heinry.fr


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