[theora] Are two passes useful in CBR mode ?
Benjamin M. Schwartz
bmschwar at fas.harvard.edu
Wed Mar 17 19:59:41 PDT 2010
thibaut bethune wrote:
> I try to use the video tag to post videos on my blog
> I've read that CBR is a better choice than VBR for web publishing
> regarding the way TCP/IP works.
Yes, but there is no such thing as CBR. The equivalent of CBR in video is
buffer-constrained bitrate control, which makes sure that a user with only
K seconds of buffer will be able to play through the file while
downloading it at the target bitrate.
> I wander if the --two-pass option in ffmeg2theora is useful or not,
> since the bitrate (and then the file size) is fixed. Can i expect a
> better quality or is it a waste of time in CBR ?
Two-pass is useful when you are doing "CBR". It should improve the
overall quality of the result. When doing VBR (i.e. constant-quality),
two-pass is not helpful.
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