avcodec/vp3: Use symbols table for VP3 motion vectors

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 used for VP3 motion vectors. The reason it
hasn't been done before is probably that the array in this case
contained entries in the range -31..31; but this is no problem with
ff_init_vlc_from_lengths(): Just apply an offset of 31 to the symbols
before storing them in the table used to initialize VP3 motion vectors
and apply an offset of -31 when initializing the actual VLC.

Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@gmail.com>

diff --git a/libavcodec/vp3.c b/libavcodec/vp3.c
index 7d1d2411ab2de37f403ca47ba174288f48d360da..2f43de757ed470a58953f693bf0c56c0bcdfaa7d 100644 (file)
--- a/libavcodec/vp3.c
+++ b/libavcodec/vp3.c
@@ -48,6 +48,7 @@
 #include "vp3dsp.h"
 #include "xiph.h"
 
+#define VP3_MV_VLC_BITS     6
 #define VP4_MV_VLC_BITS     6
 #define SUPERBLOCK_VLC_BITS 6
 
@@ -946,8 +947,10 @@ static int unpack_vectors(Vp3DecodeContext *s, GetBitContext *gb)
                 case MODE_INTER_PLUS_MV:
                     /* all 6 fragments use the same motion vector */
                     if (coding_mode == 0) {
-                        motion_x[0] = motion_vector_table[get_vlc2(gb, s->motion_vector_vlc.table, 6, 2)];
-                        motion_y[0] = motion_vector_table[get_vlc2(gb, s->motion_vector_vlc.table, 6, 2)];
+                        motion_x[0] = get_vlc2(gb, s->motion_vector_vlc.table,
+                                               VP3_MV_VLC_BITS, 2);
+                        motion_y[0] = get_vlc2(gb, s->motion_vector_vlc.table,
+                                               VP3_MV_VLC_BITS, 2);
                     } else if (coding_mode == 1) {
                         motion_x[0] = fixed_motion_vector_table[get_bits(gb, 6)];
                         motion_y[0] = fixed_motion_vector_table[get_bits(gb, 6)];
@@ -976,8 +979,10 @@ static int unpack_vectors(Vp3DecodeContext *s, GetBitContext *gb)
                         current_fragment = BLOCK_Y * s->fragment_width[0] + BLOCK_X;
                         if (s->all_fragments[current_fragment].coding_method != MODE_COPY) {
                             if (coding_mode == 0) {
-                                motion_x[k] = motion_vector_table[get_vlc2(gb, s->motion_vector_vlc.table, 6, 2)];
-                                motion_y[k] = motion_vector_table[get_vlc2(gb, s->motion_vector_vlc.table, 6, 2)];
+                                motion_x[k] = get_vlc2(gb, s->motion_vector_vlc.table,
+                                                       VP3_MV_VLC_BITS, 2);
+                                motion_y[k] = get_vlc2(gb, s->motion_vector_vlc.table,
+                                                       VP3_MV_VLC_BITS, 2);
                             } else if (coding_mode == 1) {
                                 motion_x[k] = fixed_motion_vector_table[get_bits(gb, 6)];
                                 motion_y[k] = fixed_motion_vector_table[get_bits(gb, 6)];
@@ -2479,9 +2484,11 @@ static av_cold int vp3_decode_init(AVCodecContext *avctx)
     if (ret < 0)
         return ret;
 
-    if ((ret = init_vlc(&s->motion_vector_vlc, 6, 63,
-                        &motion_vector_vlc_table[0][1], 2, 1,
-                        &motion_vector_vlc_table[0][0], 2, 1, 0)) < 0)
+    ret = ff_init_vlc_from_lengths(&s->motion_vector_vlc, VP3_MV_VLC_BITS, 63,
+                                   &motion_vector_vlc_table[0][1], 2,
+                                   &motion_vector_vlc_table[0][0], 2, 1,
+                                   -31, 0, avctx);
+    if (ret < 0)
         return ret;
 
 #if CONFIG_VP4_DECODER

diff --git a/libavcodec/vp3data.h b/libavcodec/vp3data.h
index ae2b44f533a30dbf36d57efdbd02419ddca41c29..1fbeac731b0551f0a23ff1b5a74036648be09bdb 100644 (file)
--- a/libavcodec/vp3data.h
+++ b/libavcodec/vp3data.h
@@ -112,41 +112,17 @@ static const uint8_t mode_code_vlc_len[8] = {
 };
 
 static const uint8_t motion_vector_vlc_table[63][2] = {
-    {    0, 3 },
-    {    1, 3 },
-    {    2, 3 },
-
-    {    6, 4 }, {    7, 4 },
-
-    {    8, 4 }, {    9, 4 },
-
-    {   40, 6 }, {   41, 6 }, {   42, 6 }, {   43, 6 },
-    {   44, 6 }, {   45, 6 }, {   46, 6 }, {   47, 6 },
-
-    {   96, 7 }, {   97, 7 }, {   98, 7 }, {   99, 7 },
-    {  100, 7 }, {  101, 7 }, {  102, 7 }, {  103, 7 },
-    {  104, 7 }, {  105, 7 }, {  106, 7 }, {  107, 7 },
-    {  108, 7 }, {  109, 7 }, {  110, 7 }, {  111, 7 },
-
-    { 0xE0, 8 }, { 0xE1, 8 }, { 0xE2, 8 }, { 0xE3, 8 },
-    { 0xE4, 8 }, { 0xE5, 8 }, { 0xE6, 8 }, { 0xE7, 8 },
-    { 0xE8, 8 }, { 0xE9, 8 }, { 0xEA, 8 }, { 0xEB, 8 },
-    { 0xEC, 8 }, { 0xED, 8 }, { 0xEE, 8 }, { 0xEF, 8 },
-
-    { 0xF0, 8 }, { 0xF1, 8 }, { 0xF2, 8 }, { 0xF3, 8 },
-    { 0xF4, 8 }, { 0xF5, 8 }, { 0xF6, 8 }, { 0xF7, 8 },
-    { 0xF8, 8 }, { 0xF9, 8 }, { 0xFA, 8 }, { 0xFB, 8 },
-    { 0xFC, 8 }, { 0xFD, 8 }, { 0xFE, 8 }, { 0xFF, 8 }
-};
-
-static const int8_t motion_vector_table[63] = {
-     0,   1, -1,
-     2,  -2,
-     3,  -3,
-     4,  -4,  5,  -5,  6,  -6,  7,  -7,
-     8,  -8,  9,  -9, 10, -10, 11, -11, 12, -12, 13, -13, 14, -14, 15, -15,
-    16, -16, 17, -17, 18, -18, 19, -19, 20, -20, 21, -21, 22, -22, 23, -23,
-    24, -24, 25, -25, 26, -26, 27, -27, 28, -28, 29, -29, 30, -30, 31, -31
+    { 31,  3 }, { 32,  3 }, { 30,  3 }, { 33,  4 }, { 29,  4 }, { 34,  4 },
+    { 28,  4 }, { 35,  6 }, { 27,  6 }, { 36,  6 }, { 26,  6 }, { 37,  6 },
+    { 25,  6 }, { 38,  6 }, { 24,  6 }, { 39,  7 }, { 23,  7 }, { 40,  7 },
+    { 22,  7 }, { 41,  7 }, { 21,  7 }, { 42,  7 }, { 20,  7 }, { 43,  7 },
+    { 19,  7 }, { 44,  7 }, { 18,  7 }, { 45,  7 }, { 17,  7 }, { 46,  7 },
+    { 16,  7 }, { 47,  8 }, { 15,  8 }, { 48,  8 }, { 14,  8 }, { 49,  8 },
+    { 13,  8 }, { 50,  8 }, { 12,  8 }, { 51,  8 }, { 11,  8 }, { 52,  8 },
+    { 10,  8 }, { 53,  8 }, {  9,  8 }, { 54,  8 }, {  8,  8 }, { 55,  8 },
+    {  7,  8 }, { 56,  8 }, {  6,  8 }, { 57,  8 }, {  5,  8 }, { 58,  8 },
+    {  4,  8 }, { 59,  8 }, {  3,  8 }, { 60,  8 }, {  2,  8 }, { 61,  8 },
+    {  1,  8 }, { 62,  8 }, {  0,  8 },
 };
 
 static const int8_t fixed_motion_vector_table[64] = {