[FFmpeg-user] Bad Quality Webm video with alpha

Rafael Mancini rafaelbmancini at gmail.com
Thu Sep 27 00:21:39 EEST 2018

Thanks a lot for your answer.

The WebM format is ideal for what I'm trying to do, which is alpha video
with good quality and decent size. It used to be the .flv which got

So I changed the command to Constant Quality: *ffmpeg -r 24 -i
InputFileName_%04d.png" -c:v libvpx-vp9 -crf 20 -b:v 0 OutputFileName.webm*

The quality is controled by the "-crf 20". I also tried the value of 30 but
only got really good quality at 20.

The file size is not what I expected. I got 32.5 MB for an 8 second video.
Idealy this value should be around 10-15 MB.

Any ideas on how to get a smaller file without loosing too much quality?

Em qua, 26 de set de 2018 às 13:11, Carl Eugen Hoyos <ceffmpeg at gmail.com>

> 2018-09-25 1:14 GMT+02:00, Rafael Mancini <rafaelbmancini at gmail.com>:
> > I'm trying to generate a WebM video with alpha for a HTML5 template.
> > Already tried different compression settings and I'm still getting poor
> > quality results for complex videos with lots of animated objects.
> >
> > The Input video is made in After Effects. Its a short 8 seconds video.
> I'm
> > using a PNG sequence with alpha, 24fps in Full HD.
> >
> > I'm using the following command line:
> >
> > ffmpeg -r 24 -i "InputFileName_%04d.png" -r 24 -b:v 10000k -bufsize
> 10000k
> > -force_key_frames expr:gte(t,n_forced*1) OutputFileName.webm
> Complete, uncut console output missing.
> (Did you confirm that this output format actually helps you?
> Afair, not many applications can read it.)
> The second "-r" is not a good idea, please try first without
> "-force_key_frames",
> you can still add it later, and please try with constant quality instead of
> bitrate first.
> Carl Eugen
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