[theora] Are two passes useful in CBR mode ?

thibaut bethune thibaut.bethune at gmail.com
Fri Feb 26 04:41:04 PST 2010


I try to use the video tag to post videos on my blog

I'm using ffmeg2theora to transcode videos in theora

Resolution of 320x240 pixels and constant bitrate (CBR) of ~400 kbps
seems to be ok for publishing on my blog.

I've read that CBR is a better choice than VBR for web publishing
regarding the way TCP/IP works.
("In TCP it takes a while for a connection to increase its bandwidth.
(And by “a while” I mean “not that long” but it’s long enough to
affect the low latency connection that we want for this use case"
http://hacks.mozilla.org/2009/09/theora-1-1-released/ )
Am i wrong ?

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 ?

Thanks in advance

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