[FFmpeg-devel] [PATCH 7/7] prores: use VLC LUTs

[Christophe Gisquet]

One indirection less, around 1% speedup.
---
 libavcodec/proresdec2.c | 16 +++++++++-------
 1 file changed, 9 insertions(+), 7 deletions(-)

diff --git a/libavcodec/proresdec2.c b/libavcodec/proresdec2.c
index b20021c622..85f81d92d3 100644
--- a/libavcodec/proresdec2.c
+++ b/libavcodec/proresdec2.c
@@ -561,12 +561,18 @@ static av_always_inline int decode_dc_coeffs(GetBitContext *gb, int16_t *out,
         prev_dc += (((code + 1) >> 1) ^ sign) - sign;
         out[0] = prev_dc;
     }
-    return 0;
+    return 0;	
 }
 
+#include "libavutil/timer.h"
+
+
 static av_always_inline int decode_ac_coeffs(AVCodecContext *avctx, GetBitContext *gb,
                                              int16_t *out, int blocks_per_slice)
 {
+	static VLC* lvl_vlc[9] = { &ac_vlc[0], &ac_vlc[1], &ac_vlc[2], &ac_vlc[3], &ac_vlc[0], &ac_vlc[4], &ac_vlc[4], &ac_vlc[4], &ac_vlc[4], };
+	static VLC* run_vlc[15] = { &ac_vlc[3], &ac_vlc[3], &ac_vlc[2], &ac_vlc[2], &ac_vlc[0], &ac_vlc[5], &ac_vlc[5], &ac_vlc[5], &ac_vlc[5],
+	                            &ac_vlc[4], &ac_vlc[4], &ac_vlc[4], &ac_vlc[4], &ac_vlc[4], &ac_vlc[4], };
     const ProresContext *ctx = avctx->priv_data;
     int block_mask, sign;
     unsigned pos, run, level;
@@ -585,9 +591,7 @@ static av_always_inline int decode_ac_coeffs(AVCodecContext *avctx, GetBitContex
             break;
 
         if (run < 15) {
-            static const uint8_t ctx_to_tbl[] = { 3, 3, 2, 2, 0, 5, 5, 5, 5, 4, 4, 4, 4, 4, 4 };
-            const VLC* tbl = ac_vlc + ctx_to_tbl[run];
-            run = get_vlc2(gb, tbl->table, PRORES_LEV_BITS, 3);
+            run = get_vlc2(gb, run_vlc[run]->table, PRORES_LEV_BITS, 3);
         } else {
             unsigned int bits = 21 - 2*av_log2(show_bits(gb, 10));
             run = READ_BITS(gb, bits) - 4; // up to 17 bits
@@ -599,9 +603,7 @@ static av_always_inline int decode_ac_coeffs(AVCodecContext *avctx, GetBitContex
         }
 
         if (level < 9) {
-            static const uint8_t ctx_to_tbl[] = { 0, 1, 2, 3, 0, 4, 4, 4, 4 };
-            const VLC* tbl = ac_vlc + ctx_to_tbl[level];
-            level = 1+get_vlc2(gb, tbl->table, PRORES_LEV_BITS, 3);
+            level = 1+get_vlc2(gb, lvl_vlc[level]->table, PRORES_LEV_BITS, 3);
         } else {
             unsigned int bits = 25 - 2*av_log2(show_bits(gb, 12));
             level = READ_BITS(gb, bits) - 4 + 1; // up to 21 bits
-- 
2.42.0