[FFmpeg-devel] [RFC][PATCH 1/4] avutil/frame: add an internal field to store the size of AVFrame

[Paul B Mahol]

On Sat, Feb 12, 2022 at 1:28 PM James Almer <jamrial at gmail.com> wrote:

> On 2/12/2022 9:25 AM, Paul B Mahol wrote:
> > On Sat, Feb 12, 2022 at 1:14 AM James Almer <jamrial at gmail.com> wrote:
> >
> >> This is unfortunately needed to remove (or reduce the awfulness) of
> certain
> >> modules violating the AVFrame API and using sizeof(AVFrame).
> >>
> >
> > Which modules?
>
> Anything using wrapped_avframe, so wrapped_avframe decoder and encoder,
> and vapoursynth demuxer, which exports wrapped_avframe packets.
>
> I gave porting the latter into a video source filter some time ago a
> try, which would let us remove the "demuxer", but never sent a patch. I
> can dig it and do that, but it will not change the fact both the
> wrapped_avframe decoder and encoder are still using sizeof(AVFrame).
>

There was some talk that out VS demuxer is slower than it should be.


>
> >
> >
> >> With this, the sizeof(AVFrame) value of the libavutil loaded at runtime
> >> can be
> >> used instead of the compile time value of whatever library included
> frame.h
> >>
> >> Signed-off-by: James Almer <jamrial at gmail.com>
> >> ---
> >> This is sucks, but at least less so than the current situation.
> >>
> >> I don't see wrapped_avframe going away anytime soon, so something must
> be
> >> done,
> >> and last time i tried to change how the packets are generated my
> approach
> >> was
> >> shut down, so here's another attempt.
> >>
> >>   libavutil/frame.c          |  3 +++
> >>   libavutil/frame_internal.h | 33 +++++++++++++++++++++++++++++++++
> >>   2 files changed, 36 insertions(+)
> >>   create mode 100644 libavutil/frame_internal.h
> >>
> >> diff --git a/libavutil/frame.c b/libavutil/frame.c
> >> index 8997c85e35..a63d2979db 100644
> >> --- a/libavutil/frame.c
> >> +++ b/libavutil/frame.c
> >> @@ -23,6 +23,7 @@
> >>   #include "cpu.h"
> >>   #include "dict.h"
> >>   #include "frame.h"
> >> +#include "frame_internal.h"
> >>   #include "imgutils.h"
> >>   #include "mem.h"
> >>   #include "samplefmt.h"
> >> @@ -33,6 +34,8 @@
> >>                  (frame)->channels == \
> >>
> av_get_channel_layout_nb_channels((frame)->channel_layout))
> >>
> >> +const size_t avpriv_avframe_size = sizeof(AVFrame);
> >> +
> >>   #if FF_API_COLORSPACE_NAME
> >>   const char *av_get_colorspace_name(enum AVColorSpace val)
> >>   {
> >> diff --git a/libavutil/frame_internal.h b/libavutil/frame_internal.h
> >> new file mode 100644
> >> index 0000000000..07c246f86a
> >> --- /dev/null
> >> +++ b/libavutil/frame_internal.h
> >> @@ -0,0 +1,33 @@
> >> +/*
> >> + * This file is part of FFmpeg.
> >> + *
> >> + * FFmpeg is free software; you can redistribute it and/or
> >> + * modify it under the terms of the GNU Lesser General Public
> >> + * License as published by the Free Software Foundation; either
> >> + * version 2.1 of the License, or (at your option) any later version.
> >> + *
> >> + * FFmpeg is distributed in the hope that it will be useful,
> >> + * but WITHOUT ANY WARRANTY; without even the implied warranty of
> >> + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
> >> + * Lesser General Public License for more details.
> >> + *
> >> + * You should have received a copy of the GNU Lesser General Public
> >> + * License along with FFmpeg; if not, write to the Free Software
> >> + * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
> >> 02110-1301 USA
> >> + */
> >> +
> >> +#ifndef AVUTIL_FRAME_INTERNAL_H
> >> +#define AVUTIL_FRAME_INTERNAL_H
> >> +
> >> +#include <stdint.h>
> >> +
> >> +#include "frame.h"
> >> +
> >> +/**
> >> + * sizeof(AVFrame). If you think you need to use it, then you need to
> >> change
> >> + * your code so you don't instead.
> >> + * Meant for exceptions like wrapped_avframe.
> >> + */
> >> +extern const size_t avpriv_avframe_size;
> >> +
> >> +#endif /* AVUTIL_FRAME_INTERNAL_H */
> >> --
> >> 2.35.1
> >>
> >> _______________________________________________
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> >>
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> >>
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