avcodec/smacker: Optimize constant 16bit audio output

Reviewed-by: Paul B Mahol <onemda@gmail.com>
Reviewed-by: Tomas Härdin <tjoppen@acc.umu.se>
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>

1 files changed, 22 insertions, 2 deletions

diff --git a/libavcodec/smacker.c b/libavcodec/smacker.c
index 179c70f1ee..5d94a54179 100644
--- a/libavcodec/smacker.c
+++ b/libavcodec/smacker.c
@@ -601,7 +601,7 @@ static int smka_decode_frame(AVCodecContext *avctx, AVFrame *frame,
     int i, res, ret;
     int unp_size;
     int bits, stereo;
-    unsigned pred[2], val;
+    unsigned pred[2], val, val2;
 
     if (buf_size <= 4) {
         av_log(avctx, AV_LOG_ERROR, "packet is too small\n");
@@ -672,7 +672,11 @@ static int smka_decode_frame(AVCodecContext *avctx, AVFrame *frame,
             pred[i] = av_bswap16(get_bits(&gb, 16));
         for(i = 0; i <= stereo; i++)
             *samples++ = pred[i];
-        for(; i < unp_size / 2; i++) {
+        unp_size /= 2;
+
+        if (vlc[0       ].table || vlc[         1].table ||
+            vlc[2*stereo].table || vlc[2*stereo+1].table) {
+        for(; i < unp_size ; i++) {
             unsigned idx = 2 * (i & stereo);
             if (get_bits_left(&gb) < 0) {
                 ret = AVERROR_INVALIDDATA;
@@ -691,6 +695,22 @@ static int smka_decode_frame(AVCodecContext *avctx, AVFrame *frame,
             pred[idx / 2] += val;
             *samples++ = pred[idx / 2];
         }
+        } else if (stereo) {
+            val  = 256*values[1] + values[0];
+            val2 = 256*values[3] + values[2];
+            for(; i < unp_size; i+=2) {
+                pred[0] += val;
+                pred[1] += val2;
+                *samples++ = pred[0];
+                *samples++ = pred[1];
+            }
+        } else {
+            val = 256*values[1] + values[0];
+            for(; i < unp_size; i++) {
+                pred[0] += val;
+                *samples++ = pred[0];
+            }
+        }
     } else { //8-bit data
         for(i = stereo; i >= 0; i--)
             pred[i] = get_bits(&gb, 8);