[theora] No quality advantage with two-pass?
remco47 at gmail.com
Fri Aug 28 19:38:48 PDT 2009
On Sat, Aug 29, 2009 at 4:22 AM, Remco<remco47 at gmail.com> wrote:
> The ffmpeg2theora chapter of the Theora Cookbook says that the only
> advantage of two-pass encoding is that you can hit a specific target
> size. But isn't it so that you can reserve bits for difficult parts of
> a video, which improves the perceived quality? It may be true that
> Theora does quite alright without two passes, but it seems like a
> no-brainer to me that two passes will always be better.
>  http://en.flossmanuals.net/TheoraCookbook/FFMPEG2Theora
Oh, I think I get it now:
* Single-pass encoding with a constant quality will use more bits for
harder parts, and deliver the best possible file size for that
particular quality level, and vice-versa.
* Single-pass encoding with a constant file size will reduce quality
for harder parts.
* Two-pass encoding with a constant quality size is senseless, since a
single pass already delivers the best possible file size for the
* Two-pass encoding with a constant file size will use the first pass
to somehow learn which quality setting will produce the target file
size. Still, the result is a file with the best possible quality for
that file size, just like with single-pass constant quality encoding.
It's impossible to get more from the encoder.
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