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

Vignesh Venkatasubramanian vigneshv at google.com
Fri Jun 5 02:04:08 CEST 2015

On Thu, Jun 4, 2015 at 4:54 PM, Michael Niedermayer <michaelni at gmx.at> wrote:
> On Thu, Jun 04, 2015 at 04:29:49PM -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
> I think its also used for opus due to discard_padding and then
> switching from simple to normal blocks

yes, but all opus frames are considered keyframes. so ReferenceBlock
is never written out for Opus Blocks.

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