[FFmpeg-devel] [PATCH 077/114] avcodec/vc1: Use symbols table for VLC for Block-level Transform Type

[Andreas Rheinhardt]

Expressions like array[get_vlc2()] can be optimized by using a symbols
table if the array is always the same for a given VLC. This requirement
is fulfilled for the VLC for the Block-level Transform Type and
therefore this commit implements this; switching from
ff_init_vlc_sparse() to ff_init_vlc_from_lengths() means that we can
also remove the codes table in the process which had the same size as
the new symbols table; the array used to translate the get_vlc2() values
to the desired form has also been removed, saving space.

Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt at gmail.com>
---
 libavcodec/vc1.c       |  7 ++++---
 libavcodec/vc1_block.c |  2 +-
 libavcodec/vc1data.c   | 30 +++++++++++++-----------------
 libavcodec/vc1data.h   |  6 +-----
 4 files changed, 19 insertions(+), 26 deletions(-)

diff --git a/libavcodec/vc1.c b/libavcodec/vc1.c
index 68180dc797..68855ae1d5 100644
--- a/libavcodec/vc1.c
+++ b/libavcodec/vc1.c
@@ -1611,9 +1611,10 @@ av_cold int ff_vc1_init_common(VC1Context *v)
                      ff_vc1_ttmb_codes[i], 2, 2, INIT_VLC_USE_NEW_STATIC);
             ff_vc1_ttblk_vlc[i].table           = &vlc_table[vlc_offs[i * 3 + 1]];
             ff_vc1_ttblk_vlc[i].table_allocated = vlc_offs[i * 3 + 2] - vlc_offs[i * 3 + 1];
-            init_vlc(&ff_vc1_ttblk_vlc[i], VC1_TTBLK_VLC_BITS, 8,
-                     ff_vc1_ttblk_bits[i], 1, 1,
-                     ff_vc1_ttblk_codes[i], 1, 1, INIT_VLC_USE_NEW_STATIC);
+            ff_init_vlc_from_lengths(&ff_vc1_ttblk_vlc[i], VC1_TTBLK_VLC_BITS, 8,
+                                     &ff_vc1_ttblk_tabs[i][0][1], 2,
+                                     &ff_vc1_ttblk_tabs[i][0][0], 2, 1,
+                                     0, INIT_VLC_USE_NEW_STATIC);
             ff_vc1_subblkpat_vlc[i].table           = &vlc_table[vlc_offs[i * 3 + 2]];
             ff_vc1_subblkpat_vlc[i].table_allocated = vlc_offs[i * 3 + 3] - vlc_offs[i * 3 + 2];
             ff_init_vlc_from_lengths(&ff_vc1_subblkpat_vlc[i], VC1_SUBBLKPAT_VLC_BITS, 15,
diff --git a/libavcodec/vc1_block.c b/libavcodec/vc1_block.c
index b8987b0015..da58a0738f 100644
--- a/libavcodec/vc1_block.c
+++ b/libavcodec/vc1_block.c
@@ -1140,7 +1140,7 @@ static int vc1_decode_p_block(VC1Context *v, int16_t block[64], int n,
     s->bdsp.clear_block(block);
 
     if (ttmb == -1) {
-        ttblk = ff_vc1_ttblk_to_tt[v->tt_index][get_vlc2(gb, ff_vc1_ttblk_vlc[v->tt_index].table, VC1_TTBLK_VLC_BITS, 1)];
+        ttblk = get_vlc2(gb, ff_vc1_ttblk_vlc[v->tt_index].table, VC1_TTBLK_VLC_BITS, 1);
     }
     if (ttblk == TT_4X4) {
         subblkpat = ~get_vlc2(gb, ff_vc1_subblkpat_vlc[v->tt_index].table, VC1_SUBBLKPAT_VLC_BITS, 1);
diff --git a/libavcodec/vc1data.c b/libavcodec/vc1data.c
index e92d9b7310..ed5e680527 100644
--- a/libavcodec/vc1data.c
+++ b/libavcodec/vc1data.c
@@ -30,13 +30,6 @@
 #include "vc1.h"
 #include "vc1data.h"
 
-/** Table for conversion between TTBLK and TTMB */
-const int ff_vc1_ttblk_to_tt[3][8] = {
-    { TT_8X4, TT_4X8, TT_8X8, TT_4X4, TT_8X4_TOP, TT_8X4_BOTTOM, TT_4X8_RIGHT, TT_4X8_LEFT },
-    { TT_8X8, TT_4X8_RIGHT, TT_4X8_LEFT, TT_4X4, TT_8X4, TT_4X8, TT_8X4_BOTTOM, TT_8X4_TOP },
-    { TT_8X8, TT_4X8, TT_4X4, TT_8X4_BOTTOM, TT_4X8_RIGHT, TT_4X8_LEFT, TT_8X4, TT_8X4_TOP }
-};
-
 const int ff_vc1_ttfrm_to_tt[4] = { TT_8X8, TT_8X4, TT_4X8, TT_4X4 };
 
 /** MV P mode - the 5th element is only used for mode 1 */
@@ -908,17 +901,20 @@ const uint8_t ff_vc1_ttmb_bits[3][16] = {
     11
   }
 };
-
 /* TTBLK (Transform Type per Block) tables */
-const uint8_t ff_vc1_ttblk_codes[3][8] = {
-    {  0,  1,  3,  5, 16, 17, 18, 19 },
-    {  3,  0,  1,  2,  3,  5,  8,  9 },
-    {  1,  0,  1,  4,  6,  7, 10, 11 }
-};
-const uint8_t ff_vc1_ttblk_bits[3][8] = {
-    {  2,  2,  2,  3,  5,  5,  5,  5 },
-    {  2,  3,  3,  3,  3,  3,  4,  4 },
-    {  2,  3,  3,  3,  3,  3,  4,  4 }
+const uint8_t ff_vc1_ttblk_tabs[3][8][2] = {
+    {
+        { TT_8X4, 2 }, { TT_4X8, 2 }, { TT_8X4_TOP, 5 }, { TT_8X4_BOTTOM, 5 },
+        { TT_4X8_RIGHT, 5 }, { TT_4X8_LEFT, 5 }, { TT_4X4, 3 }, { TT_8X8, 2 },
+    },
+    {
+        { TT_4X8_RIGHT, 3 }, { TT_4X8_LEFT, 3 }, { TT_4X4, 3 }, { TT_8X4, 3 },
+        { TT_8X4_BOTTOM, 4 }, { TT_8X4_TOP, 4 }, { TT_4X8, 3 }, { TT_8X8, 2 },
+    },
+    {
+        { TT_4X8, 3 }, { TT_4X4, 3 }, { TT_8X8, 2 }, { TT_8X4_BOTTOM, 3 },
+        { TT_8X4, 4 }, { TT_8X4_TOP, 4 }, { TT_4X8_RIGHT, 3 }, { TT_4X8_LEFT, 3 },
+    },
 };
 
 /* SUBBLKPAT tables, p93-94, reordered and offset by 1 */
diff --git a/libavcodec/vc1data.h b/libavcodec/vc1data.h
index 6b141b0f76..92d6374cb2 100644
--- a/libavcodec/vc1data.h
+++ b/libavcodec/vc1data.h
@@ -34,9 +34,6 @@
 
 #include "vlc.h"
 
-/** Table for conversion between TTBLK and TTMB */
-extern const int ff_vc1_ttblk_to_tt[3][8];
-
 extern const int ff_vc1_ttfrm_to_tt[4];
 
 /** MV P mode - the 5th element is only used for mode 1 */
@@ -149,8 +146,7 @@ extern const uint16_t ff_vc1_ttmb_codes[3][16];
 extern const uint8_t ff_vc1_ttmb_bits[3][16];
 
 /* TTBLK (Transform Type per Block) tables */
-extern const uint8_t ff_vc1_ttblk_codes[3][8];
-extern const uint8_t ff_vc1_ttblk_bits[3][8];
+extern const uint8_t ff_vc1_ttblk_tabs[3][8][2];
 
 /* SUBBLKPAT tables, p93-94, reordered and offset by 1 */
 extern const uint8_t ff_vc1_subblkpat_tabs[3][15][2];
-- 
2.25.1