diff --git a/libavcodec/mpeg4videodec.c b/libavcodec/mpeg4videodec.c index c9823807b5..e1ab9aac3a 100644 --- a/libavcodec/mpeg4videodec.c +++ b/libavcodec/mpeg4videodec.c @@ -1824,6 +1824,7 @@ 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; @@ -1919,7 +1920,7 @@ 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]; }