[FFmpeg-devel] [PATCH] lavf/matroskaenc: Write Block Keyframe correctly

[Michael Niedermayer]

On Tue, Jun 02, 2015 at 12:31:53PM -0700, Vignesh Venkatasubramanian wrote:
> Per matroska Block Structure [1], for keyframes 0th bit of the flag
> should not be set (unlike SimpleBlocks). For Blocks, keyframes is
> inferred by the absence of ReferenceBlock element (as done by
> matroskadec). This CL writes the flag correctly and inserts the
> ReferenceBlock element for non-keyframes. The timestamp inserted is
> that of the immediately preceding frame (which is true for VP8 and VP9
> - the only 2 codecs using the matroska block element as of now). It
> also considers all non-video frames (audio, subtitles, metadata) to
> be keyframes.
> 
> [1] http://www.matroska.org/technical/specs/index.html#block_structure
> 
> Signed-off-by: Vignesh Venkatasubramanian <vigneshv at google.com>
> ---
>  libavformat/matroskaenc.c | 30 +++++++++++++++++++++++-------
>  1 file changed, 23 insertions(+), 7 deletions(-)
> 
> diff --git a/libavformat/matroskaenc.c b/libavformat/matroskaenc.c
> index aa9d119..98b6500 100644
> --- a/libavformat/matroskaenc.c
> +++ b/libavformat/matroskaenc.c
> @@ -95,6 +95,10 @@ typedef struct mkv_track {
>  #define MODE_MATROSKAv2 0x01
>  #define MODE_WEBM       0x02
>  
> +/** Maximum number of tracks allowed in a Matroska file (with track numbers in
> + * range 1 to 126 (inclusive) */
> +#define MAX_TRACKS 126
> +
>  typedef struct MatroskaMuxContext {
>      const AVClass  *class;
>      int             mode;
> @@ -125,6 +129,8 @@ typedef struct MatroskaMuxContext {
>      uint32_t chapter_id_offset;
>      int wrote_chapters;
>  
> +    int64_t last_track_timestamp[MAX_TRACKS];
> +
>      int allow_raw_vfw;
>  } MatroskaMuxContext;
>  

> @@ -1354,6 +1360,7 @@ static int mkv_write_header(AVFormatContext *s)
>              version = 4;
>      }
>  
> +    memset(mkv->last_track_timestamp, 0, MAX_TRACKS);

isnt the memset redundant as the context gets zeroed on allocation ?

[...]
-- 
Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

I am the wisest man alive, for I know one thing, and that is that I know
nothing. -- Socrates
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