[x264-devel] Re: no gain in 2PASS for very low bitrates

[Loren Merritt]

On Wed, 21 Dec 2005, shauli rozen wrote:

> Hi All.
>
> I am trying to encode the a test vector with some movement to low bit 
> rate (25 fps at 40kbps ).
> I tried using both abr and 2pass , and even though 2pass gives me a 
> more accurate bit rate results
> I don't see much gain in quality over the abr.
>
> I am using the two pass by setting both b_stat_write and b_stat_read to 1,
> and then I run the encoder twice.
>
> Is it true that there is no much gain in using 2pass for really low bit rate
> ? I expected much better results in the 2pass.
>
> Maybe I am doing something wrong?

b_stat_read=1 only on the 2nd pass, right?
What resolution? At 40kbps, it better be <= QCIF.
How many frames? 2pass doesn't do much on short videos, other than giving 
more accurate bitrate. It only matters when there's many scenes of varying 
complexity.

--Loren Merritt

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