[FFmpeg-devel] [PATCH v6 1/3] avcodec: add flags for packets with top/bottom field

[wm4]

On Tue, 22 May 2018 17:19:35 -0400 (EDT)
Patrick Keroulas <patrick.keroulas at savoirfairelinux.com> wrote:

> ----- Original Message -----
> > From: "Rostislav Pehlivanov" <atomnuker at gmail.com>
> > To: "FFmpeg development discussions and patches" <ffmpeg-devel at ffmpeg.org>
> > Sent: Friday, May 18, 2018 5:28:42 PM
> > Subject: Re: [FFmpeg-devel] [PATCH v6 1/3] avcodec: add flags for packets with top/bottom field  
> 
> > On 18 May 2018 at 22:17, wm4 <nfxjfg at googlemail.com> wrote:  
> 
> 
> 
> > > But I think a new side data type would be much saner. We could even
> > > just make it something generic, like AV_PKT_DATA_ANCILLARY or
> > > something. It's apparently just packet data which somehow couldn't go
> > > into the packet data.  
> 
> 
> > I agree, a generic ancillary side data type sounds better. It would have to
> > be handled the same way as mastering metadata (e.g. to allocate it you'd
> > need to use a separate function), since the size of the data struct can't
> > be part of the API if we intend to add fields later.
> > Patrick, if you're okay with that you should submit a patch which bases
> > such side data on libavutil/mastering_display_metadata.h/.c  
> 
> No problem for transmitting field flags through side data. But the given
> example (libavutil/mastering_display_metadata.h/.c) attaches data to
> AVFrame, not AVPacket, so I'm not sure where to place this separate
> allocator function. Do you recommend to create a new 
> libavcodec/ancillary.c/h utility?

The example you mentioned exists for AVPacket too (it's just not easy
to see how it can end up in AVPacket, because no demuxer does that
directly).

Anyway, ancillary side data would just be an untyped byte array, so I
don't think it needs any helpers. Just an addition to the packet side
data enum (I think it's somewhere in avcodec.h).