X-Git-Url: https://git.sesse.net/?a=blobdiff_plain;f=libavcodec%2Fmpeg4videodec.c;h=055afabc7e25ad9f2f181f44799cc031d40c7e7b;hb=8fec9fca69c22fc41d8602d8bdf547f14c70fc06;hp=b6f2ae7b7b5220bd00475541c6c1de2f1b20b681;hpb=409e684e79b6ee0c511292326f09b13fe230e58e;p=ffmpeg

diff --git a/libavcodec/mpeg4videodec.c b/libavcodec/mpeg4videodec.c
index b6f2ae7b7b5..055afabc7e2 100644
--- a/libavcodec/mpeg4videodec.c
+++ b/libavcodec/mpeg4videodec.c
@@ -1826,6 +1826,7 @@ static int mpeg4_decode_studio_block(MpegEncContext *s, int32_t block[64], int n
     uint32_t flc;
     const int min = -1 *  (1 << (s->avctx->bits_per_raw_sample + 6));
     const int max =      ((1 << (s->avctx->bits_per_raw_sample + 6)) - 1);
+    int shift =  3 - s->dct_precision;
 
     mismatch = 1;
 
@@ -1921,7 +1922,7 @@ static int mpeg4_decode_studio_block(MpegEncContext *s, int32_t block[64], int n
             else
                 block[j] = flc;
         }
-        block[j] = ((8 * 2 * block[j] * quant_matrix[j] * s->qscale) >> s->dct_precision) / 32;
+        block[j] = ((block[j] * quant_matrix[j] * s->qscale) * (1 << shift)) / 16;
         block[j] = av_clip(block[j], min, max);
         mismatch ^= block[j];
     }
@@ -3211,7 +3212,7 @@ static int decode_studio_vol_header(Mpeg4DecContext *ctx, GetBitContext *gb)
  * Decode MPEG-4 headers.
  *
  * @param  header If set the absence of a VOP is not treated as error; otherwise, it is treated as such.
- * @return <0 if an error occured
+ * @return <0 if an error occurred
  *         FRAME_SKIPPED if a not coded VOP is found
  *         0 else
  */