[FFmpeg-devel] [PATCH 2/3] lavc: add a framework to fix alignment problems.

[Nicolas George]

A lot of codecs require aligned frame data, but do not document it.
It can result in crashes with perfectly valid uses of the API.

TODO Implementation missing.

Design rationale:

- requiring frame data to be always aligned would be wasteful;

- alignment requirements will evolve
  (the 16->32 bump is still recent);

- requiring applications to worry about alignment is not convenient.

Signed-off-by: Nicolas George <george at nsup.org>
---
 libavcodec/avcodec.h | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/libavcodec/avcodec.h b/libavcodec/avcodec.h
index 35df4f6ced..51a7e2db21 100644
--- a/libavcodec/avcodec.h
+++ b/libavcodec/avcodec.h
@@ -3644,6 +3644,16 @@ typedef struct AVCodecContext {
      *             AVCodecContext.get_format callback)
      */
     int hwaccel_flags;
+
+    /**
+     * Minimum alignment of frame data required by the codec.
+     * All frame data pointers must have the alignment lower bits cleared,
+     * i.e. be a multiple of 1<<alignment.
+     * - encoding: set by the encoder and used by the framework
+     * - decoding: unused
+     */
+    unsigned alignment;
+
 } AVCodecContext;
 
 AVRational av_codec_get_pkt_timebase         (const AVCodecContext *avctx);
-- 
2.11.0