[kdenlive] FW: KDENLIVE 0.9.10 Very Slow Rendering

[jb]

Hello,

> Hi,
> I recently had a major problem after upgrading from 0.9.6 to 0.9.10 using
> Ubuntu 12.04
> 
> I finished up spending about 2 weeks backing up, restoring, changing to
> Ubuntu 14.04 hoping that would solve the problem but it didn't.
> 
> What I found was that everything worked fine with 0.9.6 but rendering small
> clips with 0.9.10 took twice the time. Larger clips just seemed to clog up
> and die.
> 
> After a lot of investigation I found out that it is the MLT rendering
> profiles which are causing the problems. In 0.9.6 the typical profile for
> an MPEG2 file render was :-
> 
> 
> f=mpeg acodec=mp2 ab=%audiobitrate+'k' ar=48000 vcodec=mpeg2video minrate=0
> vb=%bitrate+'k' bf=2 b_strategy=1 trellis=1 aspect=%dar pass=%passesWhere
> in 0.9.10 the number of profiles was significantly reduced and the number
> of parameters has substantially reduced, the main culprit being the
> replacement 0f "f=mpeg" for "properties = MPEG-2" or something like that, I
> no longer have 0.9.10 loaded having gone back to 0.9.6 so I cant remember
> exactly what the MLT parameters are.
> 
> The main problem is that the new profile takes at least twice as long to
> render, but when the script is running it provides an estimated time
> remaing which counts down (slowly) and then seems to stop at just a few
> seconds remaining or 0 remaining where it sits for about the same time
> again as the rendering all ready took. For short clips this is just an
> incovenience but for longer clips it can sit there apparently frozen for
> hours.

Maintaining profiles for the many file formats supported by Kdenlive is not an 
easy task. So at some point, before the 0.9.10 release, it was decided to 
switch to the profiles provided by MLT with some minor customization.

The MLT presets are simple text files with FFmpeg properties, that are 
installed in:
$INSTALL_DIR/share/mlt/presets/consumer/avformat

I did some tests with the MPEG-2 profile, and you are right, it takes almost 
twice the time to render, compared to the older settings.

The difference is in some parameters set in the MLT preset:
mbd=rd
cmp=satd
subcmp=satd

This is probably supposed to enhance quality, but as you noticed, you can 
always edit the Kdenlive rendring profile to manually set whatever properties 
you want.

regards
jb