[x264-devel] Problem on transform_bypass

[Jin Lei]

Dear all:

        I want to apply *transfrom_bypass *mode to a part of macroblocks in
a video(with several sequences concluded), but x264 only support compressing
all the macroblocks of all frames in lossless mode. Therefore, I make some
modification on x264. I try a few methods only to get a yuv output that is
decoded incorrectly. I use JM17.2 and ffmpeg（the version supports high444)
to test my encoded videos. Both of them cannot give the output expected.

       The methods I tried are:
       1. set *h->sps->b_qpprime_y_zero_transform_bypass=1 *in *
x264_sps_init*(set.c).
           set set* h->mb.i_qp=0* at the end of
*x264_macroblock_analyse*(analyse.c),
if some conditions are meet.
           And according to the values of the variables metioned
above( *if(h->sps->b_qpprime_y_zero_transform_bypass==1&&set
h->mb.i_qp==0)*), it is   judged that whether *h->mb.b_lossless=1* or not,
just after the statement "*h->mb.i_qp=0*"(analyse.c).


       2. set *h->sps->b_qpprime_y_zero_transform_bypass=1* in *
x264_sps_init*(set.c).
           set *h->mb.i_qp=0* in *x264_macroblock_analyse* before *
x264_mb_analyse_init*(analyse.c), if some conditions are meet.
           The x264 program contains serveral statements like
*if(h->mb.b_lossless)
x264_predict_lossless_x*x()* or  *if(h->mb.b_lossless)* then the operations
of DCT and quantization are skipped(these results can be get by seaching
reference in vs2005). I add the condition that "*||(h->mb.i_qp==0 &&
h->sps->b_qpprime_y_zero_transform_bypass==1*" into these IFs.

      Both of the methods above cannot get the correct result.

      Would you please give me some ideas of the right way of achieving the
good results.
      Thanks a lot!


your sincerely

JinLei from China
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