shithub: libvpx

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Use lossless for Q0

The commit changes the coding mode to lossless whenever the lowest
quantizer is choosen.

As expected, test results showed no difference for cif and std-hd
set where Q0 is rarely used. For yt and yt-hd set, Q0 is used for
a number of clips, where this commit helped a lot in the high end.

Average over all clips in the sets:
yt: 2.391% 1.017% 1.066%
hd: 1.937%  .764%  .787%

Change-Id: I9fa9df8646fd70cb09ffe9e4202b86b67da16765

--- a/vp9/common/vp9_blockd.h

+++ b/vp9/common/vp9_blockd.h

@@ -140,7 +140,7 @@

 #define VP9_MVREFS (1 + SPLITMV - NEARESTMV)

 #if CONFIG_LOSSLESS

-#define WHT_UPSCALE_FACTOR 3

+#define WHT_UPSCALE_FACTOR 2

 #endif

 typedef enum {

--- a/vp9/encoder/vp9_bitstream.c

+++ b/vp9/encoder/vp9_bitstream.c

@@ -1673,8 +1673,8 @@

   pc->sb32_coded = get_binary_prob(cpi->sb32_count[0], cpi->sb32_count[1]);

   vp9_write_literal(&header_bc, pc->sb32_coded, 8);

 #if CONFIG_LOSSLESS

-  vp9_write_bit(&header_bc, cpi->oxcf.lossless);

-  if (cpi->oxcf.lossless) {

+  vp9_write_bit(&header_bc, cpi->mb.e_mbd.lossless);

+  if (cpi->mb.e_mbd.lossless) {

     pc->txfm_mode = ONLY_4X4;

   }

   else

--- a/vp9/encoder/vp9_encodeframe.c

+++ b/vp9/encoder/vp9_encodeframe.c

@@ -30,7 +30,7 @@

 #include "vp9/common/vp9_seg_common.h"

 #include "vp9/common/vp9_tile_common.h"

 #include "vp9/encoder/vp9_tokenize.h"

-#include "vp9_rtcd.h"

+#include "./vp9_rtcd.h"

 #include <stdio.h>

 #include <math.h>

 #include <limits.h>

@@ -1225,6 +1225,25 @@

   if (cm->full_pixel)

     xd->fullpixel_mask = 0xfffffff8;

 }

+#if CONFIG_LOSSLESS

+static void switch_lossless_mode(VP9_COMP *cpi, int lossless) {

+  if (lossless) {

+    cpi->mb.fwd_txm8x4            = vp9_short_walsh8x4_x8;

+    cpi->mb.fwd_txm4x4            = vp9_short_walsh4x4_x8;

+    cpi->mb.e_mbd.inv_txm4x4_1    = vp9_short_inv_walsh4x4_1_x8;

+    cpi->mb.e_mbd.inv_txm4x4      = vp9_short_inv_walsh4x4_x8;

+    cpi->mb.optimize              = 0;

+    cpi->common.filter_level      = 0;

+    cpi->zbin_mode_boost_enabled  = FALSE;

+    cpi->common.txfm_mode         = ONLY_4X4;

+  } else {

+    cpi->mb.fwd_txm8x4            = vp9_short_fdct8x4;

+    cpi->mb.fwd_txm4x4            = vp9_short_fdct4x4;

+    cpi->mb.e_mbd.inv_txm4x4_1    = vp9_short_idct4x4llm_1;

+    cpi->mb.e_mbd.inv_txm4x4      = vp9_short_idct4x4llm;

+  }

+}

+#endif

 static void encode_frame_internal(VP9_COMP *cpi) {

   int mb_row;

@@ -1282,6 +1301,14 @@

   vp9_zero(cpi->mb_mv_ref_count);

 #endif

+#if CONFIG_LOSSLESS

+  // force lossless mode when Q0 is selected

+  cpi->mb.e_mbd.lossless = (cm->base_qindex == 0 &&

+                            cm->y1dc_delta_q == 0 &&

+                            cm->uvdc_delta_q == 0 &&

+                            cm->uvac_delta_q == 0);

+  switch_lossless_mode(cpi, cpi->mb.e_mbd.lossless);

+#endif

   vp9_frame_init_quantizer(cpi);

   vp9_initialize_rd_consts(cpi, cm->base_qindex + cm->y1dc_delta_q);

--- a/vp9/encoder/vp9_onyx_if.c

+++ b/vp9/encoder/vp9_onyx_if.c

@@ -847,7 +847,7 @@

   cpi->mb.fwd_txm4x4    = vp9_short_fdct4x4;

 #if CONFIG_LOSSLESS

-  if (cpi->oxcf.lossless) {

+  if (cpi->oxcf.lossless || cpi->mb.e_mbd.lossless) {

     cpi->mb.fwd_txm8x4    = vp9_short_walsh8x4_x8;

     cpi->mb.fwd_txm4x4    = vp9_short_walsh4x4_x8;

   }

@@ -2469,7 +2469,7 @@

     cm->filter_level = 0;

   }

 #if CONFIG_LOSSLESS

-  else if (cpi->oxcf.lossless) {

+  else if (cpi->mb.e_mbd.lossless) {

     cm->filter_level = 0;

   }

 #endif

--- a/vp9/encoder/vp9_quantize.c

+++ b/vp9/encoder/vp9_quantize.c

@@ -411,15 +411,11 @@

   for (Q = 0; Q < QINDEX_RANGE; Q++) {

     int qzbin_factor = (vp9_dc_quant(Q, 0) < 148) ? 84 : 80;

-

     int qrounding_factor = 48;

-#if CONFIG_LOSSLESS

-    if (cpi->oxcf.lossless && Q == 0) {

+    if (Q == 0) {

       qzbin_factor = 64;

       qrounding_factor = 64;

     }

-#endif

-

     // dc values

     quant_val = vp9_dc_quant(Q, cpi->common.y1dc_delta_q);

     invert_quant(cpi->Y1quant[Q] + 0,

-- 

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