video encoding for Ben

David Kuehling dvdkhlng at gmx.de
Tue Jun 7 04:51:09 EDT 2011


>>>>> "Jane" == Jane Andreas <JaneAndreas at gmx.com> writes:

> as we have a new ogg theora capability, I tried to encode both an mpg
> and ogv from the 1024-ogv version of Sintel, an open movie similar in
> spirit to Big Buck Bunny.  I used the method from the Jlime site which
> is


> ffmpeg -i your_video_file -ac 1 -ar 22050 -s 320x240 output.mpg

> and to make the ogv i just changed the .mpg suffix to .ogv

> both videos came out like crap and I am wondering why.  what did i do
> wrong and how do I fix it?

Hi Jane,

you shouldn't use ffmpeg for theora encoding.  FFmpeg's theora support
is pretty bad.  This is why the theora project has their own transcoder,
'ffmpeg2theora', which uses the ffmpeg library for decoding, but
performs much better on the encoding side.

If you still want to go with ffmpeg, I spotted a few problems with your
command:

 - you have to tell it to use the 'libvorbis' encoder for audio, else it
 will use some very low quality internal vorbis encoder

 - you should give it a target video bitrate via '-v'

 - you shuld use 44100 sample rate for audio, everything else might
    produce bad artefacts on decoding

something like:

 ffmpeg -i 1.mpeg  -ar 44100 -vb 300k  -acodec libvorbis test.ogv

but i really won't recommend it.

David
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