h264: allow cropping to AVCodecContext.width/height

Override the frame size from the SPS with AVCodecContext values
if the latter specify a size smaller by less than one macroblock.
This is required for correct cropping of MOV files from Canon cameras.

Signed-off-by: Mans Rullgard <mans@mansr.com>
(cherry picked from commit 30f515091c)

Conflicts:

	libavcodec/h264.c

libavcodec/h264.c

@@ -2605,6 +2605,12 @@ static int decode_slice_header(H264Context *h, H264Context *h0){
         s->height = s->avctx->height;
     }
 
+    if (FFALIGN(s->avctx->width,  16) == s->width &&
+        FFALIGN(s->avctx->height, 16) == s->height) {
+        s->width  = s->avctx->width;
+        s->height = s->avctx->height;
+    }
+
     if (s->context_initialized
         && (   s->width != s->avctx->width || s->height != s->avctx->height
             || av_cmp_q(h->sps.sar, s->avctx->sample_aspect_ratio))) {