[FFmpeg-devel] [PATCH]lavf/matroskaenc: Do not write 0 duration for subtitles

[Jerome Martinez]

On 12/11/2017 03:12, Carl Eugen Hoyos wrote:
> -            put_ebml_uint(pb, MATROSKA_ID_BLOCKDURATION, duration);
> +            if (duration > 0)
> +                put_ebml_uint(pb, MATROSKA_ID_BLOCKDURATION, duration);

In that case, the duration of the block is DefaultDuration (if it 
exists), completely different.
Is it intended to say that a duration of 0 at this place means that the 
block has the default block duration if it exists?

What is the use case for a duration of 0?

(Note: the meaning of the a block duration of 0 is unclear to me, I'll 
ask on CELLAR mailing list to clarify that)