Search range in H264 encoder

[nicky_hoang270582]

Hi all

I wonder if the parameter search_x (Maximum of absolute value of horizontal part of motion vector.)and search_y (Maximum of absolute value ofvertical part of motion vector.) mean the search window size in the ME process. If yes, why is it specified so small as 4x4 in the sample.par file which is included in the H264_IPP4.1 encoder? That's bcos normally, we deal with 16x16 or 8x8. Can you tell me the meaning of the search x and search y below?

Thank you very much in advanced for all the help

Yours

Nicky

--------------------------------------------------------------------------

H264 Sequence.

foreman_cif.yuv /* name of source files */

300 /* number of frames */

1 299 /* 1(reserved) , N (# of frames in between I frames) */

0 /* Number of B frames between I (or P) and next P */

352 /* horizontal_size */

288 /* vertical_size */

3 /* frame_rate_code: 3 means 25 Hz, 6 means 50 Hz */

0 16 16 16 0 /* method(0 - quant_codes, 1 - CBR, quant_codes (I P B) & bitrate !!!ALL must be specified */

14 4 0 /* extra block split, search x,search_y, implicit weighted biprediction(reserved)*/

352 /* display_horizontal_size */

288 /* display_vertical_size */

[sburakov]

Hello,

search_x, search_y parameters are the ranges of search for motion estimation algorithm. The values set for 4 in sample.par file just as an example. You can vary these numbers. Values 8 and 16 are also possible.

With best regards,

Sergey.

[andrewk88]

FYI

Based on my analysis, so very limited search range is still working reasonable well, becausesearching isnotrestrictedby absolute values of

search x and search y

butthese are justrelativelimits around a best initial motion predictor (see umc_h264_me.cpp for more details)