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Add option to perform multiple trellis quantization iterations

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Multiple trellis iterations may improve coding performance as Huffman
tables are updated with each iteration. In practice the benefit appears
to be very minimal
This commit is contained in:
Frank Bossen
2014-04-01 23:14:29 +02:00
parent 2012e32f19
commit 1733487e17
3 changed files with 6 additions and 4 deletions
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8
jcmaster.c
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@@ -332,11 +332,11 @@ select_scan_parameters (j_compress_ptr cinfo)
if (master->pass_number < master->pass_number_scan_opt_base) {
cinfo->comps_in_scan = 1;
if (cinfo->use_scans_in_trellis) {
cinfo->cur_comp_info[0] = &cinfo->comp_info[master->pass_number/4];
cinfo->cur_comp_info[0] = &cinfo->comp_info[master->pass_number/(4*cinfo->trellis_num_loops)];
cinfo->Ss = (master->pass_number%4 < 2) ? 1 : cinfo->trellis_freq_split+1;
cinfo->Se = (master->pass_number%4 < 2) ? cinfo->trellis_freq_split : DCTSIZE2-1;
} else {
cinfo->cur_comp_info[0] = &cinfo->comp_info[master->pass_number/2];
cinfo->cur_comp_info[0] = &cinfo->comp_info[master->pass_number/(2*cinfo->trellis_num_loops)];
cinfo->Ss = 1;
cinfo->Se = DCTSIZE2-1;
}
@@ -900,7 +900,7 @@ jinit_c_master_control (j_compress_ptr cinfo, boolean transcode_only)
if (cinfo->trellis_quant) {
if (cinfo->progressive_mode)
master->total_passes += ((cinfo->use_scans_in_trellis) ? 4 : 2) * cinfo->num_components;
master->total_passes += ((cinfo->use_scans_in_trellis) ? 4 : 2) * cinfo->num_components * cinfo->trellis_num_loops;
else
master->total_passes += 1;
}
@@ -912,6 +912,6 @@ jinit_c_master_control (j_compress_ptr cinfo, boolean transcode_only)
for (i = 0; i < cinfo->num_scans; i++)
master->scan_buffer[i] = NULL;
master->pass_number_scan_opt_base = ((cinfo->use_scans_in_trellis) ? 4 : 2) * cinfo->num_components;
master->pass_number_scan_opt_base = ((cinfo->use_scans_in_trellis) ? 4 : 2) * cinfo->num_components * cinfo->trellis_num_loops;
}
}

1
jcparam.c
View File

@@ -432,6 +432,7 @@ jpeg_set_defaults (j_compress_ptr cinfo)
cinfo->use_scans_in_trellis = FALSE;
cinfo->trellis_freq_split = 8;
cinfo->trellis_num_loops = 1;
}

1
jpeglib.h
View File

@@ -386,6 +386,7 @@ struct jpeg_compress_struct {
boolean trellis_passes; /* TRUE=currently doing trellis-related passes */
int trellis_freq_split; /* splitting point for frequency in trellis quantization */
int trellis_num_loops; /* number of trellis loops */
int num_scans_luma; /* # of entries in scan_info array pertaining to luma (used when optimize_scans is TRUE */
int num_scans_luma_dc;