[FFmpeg-devel] [PATCH] avutil/frame: document data alignment restriction

[Nicolas George]

Le quartidi 4 thermidor, an CCXXV, Muhammad Faiz a écrit :
> The behaviour is based on assumptions:
>     - copying audio data is cheap, so keeping data alignment is cheap,
>     - copying video data is not cheap, so keeping data alignment is not cheap,
>       e.g. crop filter.
> 
> Should fix Ticket6349.

> Note that after fc3a03fcf9cd7eafe7342e2508e6128888efa0bb, the crash has
> been fixed.

s/fixed/worked around in the most common situations/

> 
> Signed-off-by: Muhammad Faiz <mfcc64 at gmail.com>
> ---
>  libavutil/frame.h | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/libavutil/frame.h b/libavutil/frame.h
> index 26261d7e40..1b08eec231 100644
> --- a/libavutil/frame.h
> +++ b/libavutil/frame.h
> @@ -202,6 +202,9 @@ typedef struct AVFrame {
>       * up to 16 bytes beyond the planes, if these filters are to be used,
>       * then 16 extra bytes must be allocated.
>       *

> +     * For audio, the data should be aligned to CPUs alignment preference.

I think this is a bad idea: it is an API change, and a rather bad one on
top of that:

- The "CPUs alignment preference" is not documented.

- Requiring the application to take care of it when it could be done by
  the library is a waste of effort.

> +     * For video, no restriction on the alignment.
> +     *
>       * NOTE: Except for hwaccel formats, pointers not needed by the format
>       * MUST be set to NULL.
>       */

Regards,

-- 
  Nicolas George
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