avcodec/cook: Avoid big length tables for VLC initialization

Permuting the tables used to initialize the Cook VLCs so that the code
tables are ordered from left to right in the tree revealed that the
length of the codes are ascending from left to right. Therefore one can
run-length encode them to avoid the big length tables; this saves a bit
more than 1KB.
Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@gmail.com>

libavcodec/cook.c

@@ -190,6 +190,21 @@ static av_cold void init_gain_table(COOKContext *q)
                                (1.0 / (double) q->gain_size_factor));
 }
 
+static av_cold int build_vlc(VLC *vlc, int nb_bits, const uint8_t counts[16],
+                             const void *syms, int symbol_size, int offset,
+                             void *logctx)
+{
+    uint8_t lens[MAX_COOK_VLC_ENTRIES];
+    unsigned num = 0;
+
+    for (int i = 0; i < 16; i++)
+        for (unsigned count = num + counts[i]; num < count; num++)
+            lens[num] = i + 1;
+
+    return ff_init_vlc_from_lengths(vlc, nb_bits, num, lens, 1,
+                                    syms, symbol_size, symbol_size,
+                                    offset, 0, logctx);
+}
 
 static av_cold int init_cook_vlc_tables(COOKContext *q)
 {
@@ -197,27 +212,24 @@ static av_cold int init_cook_vlc_tables(COOKContext *q)
 
     result = 0;
     for (i = 0; i < 13; i++) {
-        result |= ff_init_vlc_from_lengths(&q->envelope_quant_index[i], 9, 24,
-                                           envelope_quant_index_huffbits[i], 1,
-                                           envelope_quant_index_huffsyms[i], 1, 1,
-                                           -12, 0, q->avctx);
+        result |= build_vlc(&q->envelope_quant_index[i], 9,
+                            envelope_quant_index_huffcounts[i],
+                            envelope_quant_index_huffsyms[i], 1, -12, q->avctx);
     }
     av_log(q->avctx, AV_LOG_DEBUG, "sqvh VLC init\n");
     for (i = 0; i < 7; i++) {
         int sym_size = 1 + (i == 3);
-        result |= ff_init_vlc_from_lengths(&q->sqvh[i], vhvlcsize_tab[i], vhsize_tab[i],
-                                           cvh_huffbits[i], 1,
-                                           cvh_huffsyms[i], sym_size, sym_size,
-                                           0, 0, q->avctx);
+        result |= build_vlc(&q->sqvh[i], vhvlcsize_tab[i],
+                            cvh_huffcounts[i],
+                            cvh_huffsyms[i], sym_size, 0, q->avctx);
     }
 
     for (i = 0; i < q->num_subpackets; i++) {
         if (q->subpacket[i].joint_stereo == 1) {
-            result |= ff_init_vlc_from_lengths(&q->subpacket[i].channel_coupling, 6,
-                                               (1 << q->subpacket[i].js_vlc_bits) - 1,
-                                               ccpl_huffbits[q->subpacket[i].js_vlc_bits - 2], 1,
-                                               ccpl_huffsyms[q->subpacket[i].js_vlc_bits - 2], 1, 1,
-                                               0, 0, q->avctx);
+            result |= build_vlc(&q->subpacket[i].channel_coupling, 6,
+                                ccpl_huffcounts[q->subpacket[i].js_vlc_bits - 2],
+                                ccpl_huffsyms[q->subpacket[i].js_vlc_bits - 2], 1,
+                                0, q->avctx);
             av_log(q->avctx, AV_LOG_DEBUG, "subpacket %i Joint-stereo VLC used.\n", i);
         }
     }