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

Rostislav Pehlivanov atomnuker at gmail.com
Fri May 18 22:09:02 EEST 2018


On 18 May 2018 at 20:05, 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: Tuesday, May 15, 2018 4:46:02 PM
> > Subject: Re: [FFmpeg-devel] [PATCH v6 1/3] avcodec: add flags for
> packets with top/bottom field
>
> > On 15 May 2018 at 18:03, wm4 <nfxjfg at googlemail.com> wrote:
> >
> >> On Tue, 15 May 2018 17:15:05 +0100
> >> Rostislav Pehlivanov <atomnuker at gmail.com> wrote:
> >>
> >> > On 15 May 2018 at 15:55, wm4 <nfxjfg at googlemail.com> wrote:
> >> >
> >> > > On Mon, 14 May 2018 18:26:35 -0400
> >> > > Patrick Keroulas <patrick.keroulas at savoirfairelinux.com> wrote:
> >> > >
> >> > > > Signed-off-by: Patrick Keroulas <patrick.keroulas@
> >> savoirfairelinux.com>
> >> > > > ---
> >> > > > doc/APIchanges | 3 +++
> >> > > > libavcodec/avcodec.h | 8 ++++++++
> >> > > > libavcodec/version.h | 4 ++--
> >> > > > 3 files changed, 13 insertions(+), 2 deletions(-)
> >> > > >
> >> > > > diff --git a/doc/APIchanges b/doc/APIchanges
> >> > > > index bbefc83..d06868e 100644
> >> > > > --- a/doc/APIchanges
> >> > > > +++ b/doc/APIchanges
> >> > > > @@ -15,6 +15,9 @@ libavutil: 2017-10-21
> >> > > >
> >> > > > API changes, most recent first:
> >> > > >
> >> > > > +2018-05-xx - xxxxxxxxxx - lavc 58.20.100 - avcodec.h
> >> > > > + Add AV_PKT_FLAG_TOP_FIELD and AV_PKT_FLAG_BOTTOM_FIELD.
> >> > > > +
> >> > > > 2018-05-xx - xxxxxxxxxx - lavu 56.18.101 - hwcontext_cuda.h
> >> > > > Add AVCUDADeviceContext.stream.
> >> > > >
> >> > > > diff --git a/libavcodec/avcodec.h b/libavcodec/avcodec.h
> >> > > > index fb0c6fa..14811be 100644
> >> > > > --- a/libavcodec/avcodec.h
> >> > > > +++ b/libavcodec/avcodec.h
> >> > > > @@ -1480,6 +1480,14 @@ typedef struct AVPacket {
> >> > > > */
> >> > > > #define AV_PKT_FLAG_DISPOSABLE 0x0010
> >> > > >
> >> > > > +/**
> >> > > > + * The packet contains a top field.
> >> > > > + */
> >> > > > +#define AV_PKT_FLAG_TOP_FIELD 0x0020
> >> > > > +/**
> >> > > > + * The packet contains a bottom field.
> >> > > > + */
> >> > > > +#define AV_PKT_FLAG_BOTTOM_FIELD 0x0040
> >> > > >
> >> > > > enum AVSideDataParamChangeFlags {
> >> > > > AV_SIDE_DATA_PARAM_CHANGE_CHANNEL_COUNT = 0x0001,
> >> > > > diff --git a/libavcodec/version.h b/libavcodec/version.h
> >> > > > index 3fda743..b9752ce 100644
> >> > > > --- a/libavcodec/version.h
> >> > > > +++ b/libavcodec/version.h
> >> > > > @@ -28,8 +28,8 @@
> >> > > > #include "libavutil/version.h"
> >> > > >
> >> > > > #define LIBAVCODEC_VERSION_MAJOR 58
> >> > > > -#define LIBAVCODEC_VERSION_MINOR 19
> >> > > > -#define LIBAVCODEC_VERSION_MICRO 101
> >> > > > +#define LIBAVCODEC_VERSION_MINOR 20
> >> > > > +#define LIBAVCODEC_VERSION_MICRO 100
> >> > > >
> >> > > > #define LIBAVCODEC_VERSION_INT AV_VERSION_INT(LIBAVCODEC_
> VERSION_MAJOR,
> >>
> >> > > \
> >> > > >
> >> > > LIBAVCODEC_VERSION_MINOR, \
> >> > >
> >> > > So far we could avoid codec-specific packet flags, and I think it
> >> > > should stay this way. Maybe make it side data, something with naming
> >> > > specific to the bitpacked codec. Or alternatively, if this codec
> >> > > is 100% RTP specific and there's no such thing as standard bitpacked
> >> > > packets (e.g. muxed in other files etc.), add it to the packet
> >> > > directly. The RTP code "repacks" it already on the libavformat side
> >> > > anyway.
> >> > > _______________________________________________
> >> > > ffmpeg-devel mailing list
> >> > > ffmpeg-devel at ffmpeg.org
> >> > > http://ffmpeg.org/mailman/listinfo/ffmpeg-devel
> >> > >
> >> >
> >> > This codec isn't RTP specific, its the same as V210. There are no
> flags
> >> in
> >> > the bitstream, its just a sequence of packed pixels. And just like
> v210
> >> > there's a standard for what packets need to look like (rfc4175, and
> >> > unfortunately it does specify the fields need to be separate), so
> >> packing 2
> >> > fields in the muxer isn't really an option.
> >>
> >> Then why are there separate bitpacked and v210 decoders/codec_ids?
> >>
> >
> > Its a different type of packing.
> >
> >
> >
> >> > Side data seems a bit of an overkill for a flag. I'd say the field
> flags
> >> > are not codec specific as some raw codecs and containers can signal
> >> fields
> >> > per packet. So I don't really mind them.
> >>
> >> You want codec specific flags to accumulate in AVPacket.flags? Can't way
> >> until we change the flags field to int128_t.
> >>
> >>
> > No, but I think 2 more bits won't hurt much, especially considering
> pretty
> > much all formats supporting interlaced content split each field into a
> > separate packet.
>
> Recomposing a frame from fields on the demux side would make the bitpacked
> decoder
> completely useless. Can we find a consensus? How about reusing
> AVPictureStructure
> as suggested by Derek?
>
> > _______________________________________________
> > ffmpeg-devel mailing list
> > ffmpeg-devel at ffmpeg.org
> > http://ffmpeg.org/mailman/listinfo/ffmpeg-devel
> _______________________________________________
> ffmpeg-devel mailing list
> ffmpeg-devel at ffmpeg.org
> http://ffmpeg.org/mailman/listinfo/ffmpeg-devel
>

Reusing that structure would mean adding a field to AVPackets. I'd rather
avoid that, so I'm okay with the packet flags.


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