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avcodec/mpegvideo: remove redundant workaround to recalculate last nonzero coefficient 

The x86 optimized dct_quantize only calculates the last nonzero
coefficient correctly if the zigzag scan order is used. For the
alternate scan order, this value is incorrect.

To work around this, the dct_unquantize functions process the entire
block if the alternate scan order is used.

But a second workaround (bb198e198a) was added that recalculates the
last nonzero coefficient after dct_quantize is called if the alternate
scan order is used.

This commit removes the first workaround, which became redundant.
This commit is contained in:
Ramiro Polla 2024-08-22 01:24:54 +02:00
parent b6f7271fa9
commit 4f7aeffd8c
2 changed files with 5 additions and 10 deletions
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9
libavcodec/mpegvideo.c
View File

@ -110,8 +110,7 @@ static void dct_unquantize_mpeg2_intra_c(MpegEncContext *s,
if (s->q_scale_type) qscale = ff_mpeg2_non_linear_qscale[qscale];
else qscale <<= 1;
if(s->alternate_scan) nCoeffs= 63;
else nCoeffs= s->block_last_index[n];
nCoeffs= s->block_last_index[n];
block[0] *= n < 4 ? s->y_dc_scale : s->c_dc_scale;
quant_matrix = s->intra_matrix;
@ -141,8 +140,7 @@ static void dct_unquantize_mpeg2_intra_bitexact(MpegEncContext *s,
if (s->q_scale_type) qscale = ff_mpeg2_non_linear_qscale[qscale];
else qscale <<= 1;
if(s->alternate_scan) nCoeffs= 63;
else nCoeffs= s->block_last_index[n];
nCoeffs= s->block_last_index[n];
block[0] *= n < 4 ? s->y_dc_scale : s->c_dc_scale;
sum += block[0];
@ -175,8 +173,7 @@ static void dct_unquantize_mpeg2_inter_c(MpegEncContext *s,
if (s->q_scale_type) qscale = ff_mpeg2_non_linear_qscale[qscale];
else qscale <<= 1;
if(s->alternate_scan) nCoeffs= 63;
else nCoeffs= s->block_last_index[n];
nCoeffs= s->block_last_index[n];
quant_matrix = s->inter_matrix;
for(i=0; i<=nCoeffs; i++) {

6
libavcodec/x86/mpegvideo.c
View File

@ -312,8 +312,7 @@ static void dct_unquantize_mpeg2_intra_mmx(MpegEncContext *s,
if (s->q_scale_type) qscale = ff_mpeg2_non_linear_qscale[qscale];
else qscale <<= 1;
if(s->alternate_scan) nCoeffs= 63; //FIXME
else nCoeffs= s->intra_scantable.raster_end[ s->block_last_index[n] ];
nCoeffs= s->intra_scantable.raster_end[ s->block_last_index[n] ];
if (n < 4)
block0 = block[0] * s->y_dc_scale;
@ -380,8 +379,7 @@ static void dct_unquantize_mpeg2_inter_mmx(MpegEncContext *s,
if (s->q_scale_type) qscale = ff_mpeg2_non_linear_qscale[qscale];
else qscale <<= 1;
if(s->alternate_scan) nCoeffs= 63; //FIXME
else nCoeffs= s->intra_scantable.raster_end[ s->block_last_index[n] ];
nCoeffs= s->intra_scantable.raster_end[ s->block_last_index[n] ];
quant_matrix = s->inter_matrix;
__asm__ volatile(