On Wed, 23 May 2018 20:25:34 +0100 Rostislav Pehlivanov <atomnu...@gmail.com> wrote:
> On 23 May 2018 at 20:01, wm4 <nfx...@googlemail.com> wrote: > > > On Wed, 23 May 2018 14:29:38 -0400 (EDT) > > Patrick Keroulas <patrick.kerou...@savoirfairelinux.com> wrote: > > > > > ----- Original Message ----- > > > > From: "wm4" <nfx...@googlemail.com> > > > > To: ffmpeg-devel@ffmpeg.org > > > > Sent: Wednesday, May 23, 2018 12:02:45 PM > > > > Subject: Re: [FFmpeg-devel] [PATCH v6 1/3] avcodec: add flags for > > packets with top/bottom field > > > > > > > On Wed, 23 May 2018 16:46:17 +0100 > > > > Rostislav Pehlivanov <atomnu...@gmail.com> wrote: > > > > > > > >> On 23 May 2018 at 16:18, wm4 <nfx...@googlemail.com> wrote: > > > >> > > > >> > On Tue, 22 May 2018 17:19:35 -0400 (EDT) > > > >> > Patrick Keroulas <patrick.kerou...@savoirfairelinux.com> wrote: > > > >> > > > > >> > > ----- Original Message ----- > > > >> > > > From: "Rostislav Pehlivanov" <atomnu...@gmail.com> > > > >> > > > To: "FFmpeg development discussions and patches" < > > > >> > ffmpeg-devel@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 <nfx...@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). > > > >> > _______________________________________________ > > > >> > ffmpeg-devel mailing list > > > >> > ffmpeg-devel@ffmpeg.org > > > >> > http://ffmpeg.org/mailman/listinfo/ffmpeg-devel > > > >> > > > > >> > > > >> I'd rather have it as a well defined typed array rather than a bunch > > of > > > >> bytes. Otherwise we'd start sending unknown side data info and users > > > >> wouldn't know what to do with it. > > > > > > > > Unless you're adding some meta object system for describing arbitrary > > > > types at runtime I don't know how you'd do that. > > > > > > Is that ok if I simply define a basic struct to hold the field? > > > > > > Any suggestion on where to insert the definition of this data and the > > > accessors in lavc? In a new source file? > > > > If you make it a struct, then make a new file in libavutil, with > > at least a helper to get the struct size (this is for ABI reasons, so > > we can extend the struct later). But then this side data would need a > > specific name, not a generic one like "ancillary". > > > > The display mastering thing is valid for both packets and frames, which > > might be confusing. The thing you add is needed for packets only. > > > > I'd prefer the "ancillary" name and making it just a flat byte array > > instead of a struct and something specific. The former would be like > > extradata, just per packet. > > _______________________________________________ > > ffmpeg-devel mailing list > > ffmpeg-devel@ffmpeg.org > > http://ffmpeg.org/mailman/listinfo/ffmpeg-devel > > > > A flat array would be useless and very codec specific (e.g. if you throw > that side data at one codec it would act in a different way than another > codec), a struct is the way to go here. I don't mind adding another untyped > data if there was a reason, but what we're trying to solve here is very > well defined - determine the field of each packet. I see it rather as: some obscure codec needs some bytes per packet, but out of band, so let's add a side data that does that. That side data would of course be codec specific by definition. _______________________________________________ ffmpeg-devel mailing list ffmpeg-devel@ffmpeg.org http://ffmpeg.org/mailman/listinfo/ffmpeg-devel
