[x264-devel] The size of search area in reference frames

[john sisi]

Thanks, but my version of x264 doesn't have any "--tune psnr" option.
I am using the revision 1365 (Jan 2009). How can I remedy this
problem? or what is the rule of "--tune psnr"?

John

On Mon, Jun 14, 2010 at 12:46 AM, Jason Garrett-Glaser
<darkshikari at gmail.com> wrote:
> On Mon, Jun 14, 2010 at 12:12 AM, john sisi <sisi.john1 at gmail.com> wrote:
>> I think you are right but what is the exact difference between
>> --merange and --mvrange? The default value of merange is set to 16
>> while the default value of mvrange is -1 (Auto).
>
> merange is the distance to search *from the best predictor*.  The size
> of the search space necessary to find the correct MV is not defined by
> the length of the MV, but rather by the inaccuracy of the predictors,
> which may or may not be correlated with MV length.
>
>> Ideally, full or exhaustive search must achieve the best PSNR
>> performance but I got a weird result: I encoded foreman (CIF) at
>> 256kbps with default settings and I got an average PSNR-Y of 34.26 dB
>> for a specific frame. Then I used --me "esa" to enable the exhaustive
>> search. This time I got 34.04 dB on the same frame! I expected to get
>> a higher PSNR but the result is not consistent with my expectation. I
>> use only one reference frame. But what is the problem? Thanks again,
>
> You're not using --tune psnr when comparing psnr.  Also, you should
> always use 2-pass when in bitrate mode.
>
> Dark Shikari
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