[FFmpeg-devel] [PATCH 1/2] svq1dec: Ensure that pixel format constraints are respected

[Vittorio Giovara]

YUV410P requires that sizes are divisible by 4. There seem to be
some encoders that ignore that and encode a different value in
the bitstream itself. Handle that case by exporting the relative
cropping information.
---
Alternatively it is possible to always enforce mod4 sizes and call
it a day.
Vittorio

 libavcodec/svq1dec.c | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/libavcodec/svq1dec.c b/libavcodec/svq1dec.c
index d3e60c3a4a..55047b43ce 100644
--- a/libavcodec/svq1dec.c
+++ b/libavcodec/svq1dec.c
@@ -663,7 +663,8 @@ static int svq1_decode_frame(AVCodecContext *avctx, void *data,
         return result;
     }
 
-    result = ff_set_dimensions(avctx, s->width, s->height);
+    /* sizes must be always disivible by 4 due to pixel format constraints */
+    result = ff_set_dimensions(avctx, FFALIGN(s->width, 4), FFALIGN(s->height, 4));
     if (result < 0)
         return result;
 
@@ -755,6 +756,11 @@ static int svq1_decode_frame(AVCodecContext *avctx, void *data,
     *got_frame = 1;
     result     = buf_size;
 
+    cur->crop_left   = 0;
+    cur->crop_top    = 0;
+    cur->crop_right  = FFALIGN(s->width,  4) - s->width;
+    cur->crop_bottom = FFALIGN(s->height, 4) - s->height;
+
 err:
     av_free(pmv);
     return result;
@@ -843,6 +849,7 @@ AVCodec ff_svq1_decoder = {
     .close          = svq1_decode_end,
     .decode         = svq1_decode_frame,
     .capabilities   = AV_CODEC_CAP_DR1,
+    .caps_internal  = FF_CODEC_CAP_EXPORTS_CROPPING,
     .flush          = svq1_flush,
     .pix_fmts       = (const enum AVPixelFormat[]) { AV_PIX_FMT_YUV410P,
                                                      AV_PIX_FMT_NONE },
-- 
2.17.1