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

[Jason Garrett-Glaser]

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.

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