dca: ARMv6 optimised decode_blockcode()

This is a hand-tuned version of the code with impossible parts of
the FASTDIV function ommitted.

2-5% faster overall on Cortex-A8.

Signed-off-by: Mans Rullgard <mans@mansr.com>

1 files changed, 17 insertions, 10 deletions

diff --git a/libavcodec/dca.c b/libavcodec/dca.c
index 7f7bcf9cfd..b310638dc1 100644
--- a/libavcodec/dca.c
+++ b/libavcodec/dca.c
@@ -1038,6 +1038,7 @@ static void dca_downmix(float *samples, int srcfmt,
 }
 
 
+#ifndef decode_blockcodes
 /* Very compact version of the block code decoder that does not use table
  * look-up but is slightly slower */
 static int decode_blockcode(int code, int levels, int *values)
@@ -1051,13 +1052,15 @@ static int decode_blockcode(int code, int levels, int *values)
         code = div;
     }
 
-    if (code == 0)
-        return 0;
-    else {
-        av_log(NULL, AV_LOG_ERROR, "ERROR: block code look-up failed\n");
-        return AVERROR_INVALIDDATA;
-    }
+    return code;
+}
+
+static int decode_blockcodes(int code1, int code2, int levels, int *values)
+{
+    return decode_blockcode(code1, levels, values) |
+           decode_blockcode(code2, levels, values + 4);
 }
+#endif
 
 static const uint8_t abits_sizes[7] = { 7, 10, 12, 13, 15, 17, 19 };
 static const uint8_t abits_levels[7] = { 3, 5, 7, 9, 13, 17, 25 };
@@ -1125,16 +1128,20 @@ static int dca_subsubframe(DCAContext * s, int base_channel, int block_index)
                 if (abits >= 11 || !dca_smpl_bitalloc[abits].vlc[sel].table){
                     if (abits <= 7){
                         /* Block code */
-                        int block_code1, block_code2, size, levels;
+                        int block_code1, block_code2, size, levels, err;
 
                         size = abits_sizes[abits-1];
                         levels = abits_levels[abits-1];
 
                         block_code1 = get_bits(&s->gb, size);
-                        /* FIXME Should test return value */
-                        decode_blockcode(block_code1, levels, block);
                         block_code2 = get_bits(&s->gb, size);
-                        decode_blockcode(block_code2, levels, &block[4]);
+                        err = decode_blockcodes(block_code1, block_code2,
+                                                levels, block);
+                        if (err) {
+                            av_log(s->avctx, AV_LOG_ERROR,
+                                   "ERROR: block code look-up failed\n");
+                            return AVERROR_INVALIDDATA;
+                        }
                     }else{
                         /* no coding */
                         for (m = 0; m < 8; m++)