[FFmpeg-devel] [PATCH] h264: Support multi-field closed captions by using AVBufferRef and not resetting per field

[Devin Heitmueller]

Hello,

> On Aug 16, 2018, at 6:52 AM, joshdk at ob-encoder.com wrote:
> 
> From: Kieran Kunhya <kierank at obe.tv>
> 
> ---
> This is also useful when CC is fully contained in the first field.

FWIW: I’ve been running a variant of this this patch for a while now.  It’s needed for PAFF formatted H.264 streams (i.e. slices which are sent as individual fields rather than frames), and without it those streams will not render EIA-708 captions properly.  It typically doesn’t happen with H.264 streams created by ffmpeg because libx264 only supports MBAFF encoding, but it does occur with a number of commercial hardware encoders I’ve worked with.

We can debate the mechanics of how the buffers are referenced (which is why I believe it wasn’t merged last year), but I can say that this is a very real problem and at least this patch results in those streams playing properly.

Cheers,

Devin

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Devin Heitmueller - LTN Global Communications
dheitmueller at ltnglobal.com