[theora] buggy encoder ??

Gregory Maxwell gmaxwell at gmail.com
Sun Sep 20 21:22:27 PDT 2009

On Mon, Sep 21, 2009 at 12:08 AM, Michael A. Peters <mpeters at mac.com> wrote:
> It looks like with ffmpeg2theora the -V and -A options rather than quality
> are what I'm looking for to get the filesize I want opposed to quality
> setting, and it looks like future version will do that two pass.

Ffmpeg can't do two-pass encoding of Theora yet, even with the 1.1SVN
libtheora that is capable of it, thats one of the reason for using
(the development versions of) ffmpeg2theora.

Generally quality targeted encoding will give you higher quality for
any given size; but reaching a desired size can be annoying. Two pass
mostly eliminates that gap, although there are still some cases where
two-pass fails to work especially well.

Be mindful that in libtheora 1.1 without two pass -V provides strict
buffer management, a guarantee that the  peak bitrate will not
exceeded the average more than could be covered by a configurable
finite buffer. This can be murder on quality, but it prevents streams
from stalling and needing re-buffering when they are being transmitted
at close to their average rate.  It's a stronger guarantee than is
provided by most non-commercial video encoders, but it reduces
quality. If you don't actually care about streamability, or know that
your clients will always have much more bandwidth than the stream
average rate, the guarantee can be relaxed.  (1.1 two-pass mode uses a
relaxed buffering constraint by default)

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