[FFmpeg-cvslog] avcodec/utils: Document 32 min for h264 width

[Michael Niedermayer]

ffmpeg | branch: master | Michael Niedermayer <michael at niedermayer.cc> | Fri Jul 10 18:31:42 2015 +0200| [47d077337a62f3ece41ee90a4d5000876d5c46d1] | committer: Michael Niedermayer

avcodec/utils: Document 32 min for h264 width

Suggested-by: "Ronald S. Bultje" <rsbultje at gmail.com>
Signed-off-by: Michael Niedermayer <michael at niedermayer.cc>

> http://git.videolan.org/gitweb.cgi/ffmpeg.git/?a=commit;h=47d077337a62f3ece41ee90a4d5000876d5c46d1
---

 libavcodec/utils.c |    5 +++++
 1 file changed, 5 insertions(+)

diff --git a/libavcodec/utils.c b/libavcodec/utils.c
index 925b3ed..4245b1a 100644
--- a/libavcodec/utils.c
+++ b/libavcodec/utils.c
@@ -432,6 +432,11 @@ void avcodec_align_dimensions2(AVCodecContext *s, int *width, int *height,
         // some of the optimized chroma MC reads one line too much
         // which is also done in mpeg decoders with lowres > 0
         *height += 2;
+
+        // H.264 uses edge emulation for out of frame motion vectors, for this
+        // it requires a temporary area large enough to hold a 21x21 block,
+        // increasing witdth ensure that the temporary area is large enough,
+        // the next rounded up width is 32
         *width = FFMAX(*width, 32);
     }