hevc : fix pcm(cherry picked from commit 12bbfdba1899d11044d2bd8457159fc8b4b52a76)

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

libavcodec/hevc.c

@@ -971,7 +971,7 @@ static int hls_pcm_sample(HEVCContext *s, int x0, int y0, int log2_cb_size)
     int   stride2 = s->frame->linesize[2];
     uint8_t *dst2 = &s->frame->data[2][(y0 >> s->sps->vshift[2]) * stride2 + ((x0 >> s->sps->hshift[2]) << s->sps->pixel_shift)];
 
-    int length         = cb_size * cb_size * s->sps->pcm.bit_depth + ((cb_size * cb_size) >> 1) * s->sps->pcm.bit_depth;
+    int length         = cb_size * cb_size * s->sps->pcm.bit_depth + ((cb_size * cb_size) >> 1) * s->sps->pcm.bit_depth_chroma;
     const uint8_t *pcm = skip_bytes(&s->HEVClc->cc, (length + 7) >> 3);
     int ret;