[theora] expected bitrates ?
arc at indymedia.org
Thu Aug 28 10:03:50 PDT 2003
On Thu, Aug 28, 2003 at 02:03:42AM -0400, James H. Cloos Jr. wrote:
> Fo HDTV sized 422 originals, what kind of bitrates can one expect
> theora to hit at reasonable quality?
> Or put another way, what compression ratios can one expect from
> uncompressed to theora given a target of no significant artifacts,
> and what kind of peak bitrates would the i/o system require to keep
> up with the decoder?
With VP3 you don't see the normal artifacts until really low bitrate,
since it doesn't go "blocky" like MPEG-4 based codecs do. It's really
hard to judge something like this, especially before it's out. But
since we're using VP3 pretty much out of the box (few optimisations) you
can experiment with this yourself with Quicktime + VP3 and see what
bitrate you can encode at and get the quality you're expecting.
Also, note the difference between audio and video bitrates, to make sure
you're comparing apples to apples. Audio typically takes 128k of the
stream, in Quicktime you can see the movie properties which include
seperating the video bitrate from audio bitrate.
Lastly, note the difference between encoding from a MPEG-based source
(which many HDTV sources are already in) and an uncompressed source, one
that has never been encoded to any format. The latter will always get
better quality:compression ratio, but unfortunetly hard to find for
video. Even supposidly "origional" miniDV/DV/Digital-8 is compressed
using a format similar to JPEG.
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