Quoting wm4 (2015-10-09 16:56:30)
> On Fri,  9 Oct 2015 16:26:16 +0200
> Luca Barbato <[email protected]> wrote:
> 
> > ---
> >  libavcodec/Makefile          |  1 +
> >  libavcodec/allcodecs.c       |  1 +
> >  libavcodec/avcodec.h         |  1 +
> >  libavcodec/codec_desc.c      |  7 ++++
> >  libavcodec/wrapped_avframe.c | 94 
> > ++++++++++++++++++++++++++++++++++++++++++++
> >  5 files changed, 104 insertions(+)
> >  create mode 100644 libavcodec/wrapped_avframe.c
> > 
> > diff --git a/libavcodec/Makefile b/libavcodec/Makefile
> > index ba711ae..3e57a0d 100644
> > --- a/libavcodec/Makefile
> > +++ b/libavcodec/Makefile
> > @@ -472,6 +472,7 @@ OBJS-$(CONFIG_WMV2_ENCODER)            += wmv2enc.o 
> > wmv2.o \
> >                                            msmpeg4.o msmpeg4enc.o 
> > msmpeg4data.o
> >  OBJS-$(CONFIG_WNV1_DECODER)            += wnv1.o
> >  OBJS-$(CONFIG_WS_SND1_DECODER)         += ws-snd1.o
> > +OBJS-$(CONFIG_WRAPPED_AVFRAME_ENCODER) += wrapped_avframe.o
> >  OBJS-$(CONFIG_XAN_DPCM_DECODER)        += dpcm.o
> >  OBJS-$(CONFIG_XAN_WC3_DECODER)         += xan.o
> >  OBJS-$(CONFIG_XAN_WC4_DECODER)         += xxan.o
> > diff --git a/libavcodec/allcodecs.c b/libavcodec/allcodecs.c
> > index 2d8474a..46febd5 100644
> > --- a/libavcodec/allcodecs.c
> > +++ b/libavcodec/allcodecs.c
> > @@ -292,6 +292,7 @@ void avcodec_register_all(void)
> >      REGISTER_DECODER(VP9,               vp9);
> >      REGISTER_DECODER(VQA,               vqa);
> >      REGISTER_DECODER(WEBP,              webp);
> > +    REGISTER_ENCODER(WRAPPED_AVFRAME,   wrapped_avframe);
> >      REGISTER_ENCDEC (WMV1,              wmv1);
> >      REGISTER_ENCDEC (WMV2,              wmv2);
> >      REGISTER_DECODER(WMV3,              wmv3);
> > diff --git a/libavcodec/avcodec.h b/libavcodec/avcodec.h
> > index 11ae1fc..1494d7b 100644
> > --- a/libavcodec/avcodec.h
> > +++ b/libavcodec/avcodec.h
> > @@ -300,6 +300,7 @@ enum AVCodecID {
> >      AV_CODEC_ID_DDS,
> >      AV_CODEC_ID_DXV,
> >      AV_CODEC_ID_SCREENPRESSO,
> > +    AV_CODEC_ID_WRAPPED_AVFRAME,
> >  
> >      /* various PCM "codecs" */
> >      AV_CODEC_ID_FIRST_AUDIO = 0x10000,     ///< A dummy id pointing at the 
> > start of audio codecs
> > diff --git a/libavcodec/codec_desc.c b/libavcodec/codec_desc.c
> > index d2c7a91..91c77c8 100644
> > --- a/libavcodec/codec_desc.c
> > +++ b/libavcodec/codec_desc.c
> > @@ -1169,6 +1169,13 @@ static const AVCodecDescriptor codec_descriptors[] = 
> > {
> >          .long_name = NULL_IF_CONFIG_SMALL("Screenpresso"),
> >          .props     = AV_CODEC_PROP_LOSSLESS,
> >      },
> > +    {
> > +        .id        = AV_CODEC_ID_WRAPPED_AVFRAME,
> > +        .type      = AVMEDIA_TYPE_VIDEO,
> > +        .name      = "wrapped_avframe",
> > +        .long_name = NULL_IF_CONFIG_SMALL("AVFrame to AVPacket 
> > passthrough"),
> > +        .props     = AV_CODEC_PROP_LOSSLESS,
> > +    },
> >  
> >      /* image codecs */
> >      {
> > diff --git a/libavcodec/wrapped_avframe.c b/libavcodec/wrapped_avframe.c
> > new file mode 100644
> > index 0000000..527ddda
> > --- /dev/null
> > +++ b/libavcodec/wrapped_avframe.c
> > @@ -0,0 +1,94 @@
> > +/*
> > + * AVFrame wrapper
> > + * Copyright (c) 2015 Luca Barbato
> > + *
> > + * This file is part of Libav.
> > + *
> > + * Libav 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.
> > + *
> > + * Libav 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 Libav; if not, write to the Free Software
> > + * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 
> > 02110-1301 USA
> > + */
> > +
> > +/**
> > + * @file
> > + * Simple wrapper to store an AVFrame and forward it as AVPacket.
> > + */
> > +
> > +#include "avcodec.h"
> > +#include "internal.h"
> > +
> > +#include "libavutil/internal.h"
> > +#include "libavutil/frame.h"
> > +#include "libavutil/buffer.h"
> > +#include "libavutil/pixdesc.h"
> > +
> > +static av_cold int wrapped_avframe_encode_init(AVCodecContext *avctx)
> > +{
> > +    const AVPixFmtDescriptor *desc = av_pix_fmt_desc_get(avctx->pix_fmt);
> > +
> > +#if FF_API_CODED_FRAME
> > +FF_DISABLE_DEPRECATION_WARNINGS
> > +    avctx->coded_frame->pict_type = AV_PICTURE_TYPE_I;
> > +    avctx->coded_frame->key_frame = 1;
> > +FF_ENABLE_DEPRECATION_WARNINGS
> > +#endif
> 
> Explanation?
> 
> > +    avctx->bits_per_coded_sample = av_get_bits_per_pixel(desc);
> > +
> > +    return 0;
> > +}
> > +
> > +static void wrapped_avframe_release_buffer(void *unused, uint8_t *data)
> > +{
> > +    AVFrame *frame = (AVFrame *)data;
> > +
> > +    av_frame_free(&frame);
> > +}
> > +
> > +static int wrapped_avframe_encode(AVCodecContext *avctx, AVPacket *pkt,
> > +                     const AVFrame *frame, int *got_packet)
> > +{
> > +    AVFrame *wrapped = av_frame_alloc();
> > +    int ret;
> > +
> > +    if (!wrapped)
> > +        return AVERROR(ENOMEM);
> > +
> > +
> > +    ret = av_frame_ref(wrapped, frame);
> > +    if (ret < 0)
> > +        return ret;
> > +
> > +    pkt->buf = av_buffer_create((uint8_t *)wrapped, sizeof(wrapped),
> > +                                wrapped_avframe_release_buffer, NULL,
> > +                                AV_BUFFER_FLAG_READONLY);
> > +    if (!pkt->buf) {
> > +        av_frame_free(&wrapped);
> > +        return AVERROR(ENOMEM);
> > +    }
> > +
> > +    pkt->data = (uint8_t *)wrapped;
> > +    pkt->size = sizeof(wrapped);
> > +
> 
> In theory, sizeof(AVFrame) is not allowed, because it's defined in
> libavutil, and the size of the struct is not part of the ABI. I wonder
> if this requires changing this? If everything else fails, we could just
> wrap a pointer to an AVFrame, instead of an AVFrame itself.

I think sizeof(AVFrame) is kind of ok in this case. At least I don't see
how it could seriously break anything. The receiver of such a packet
would technically not be allowed to access the fields that exist in the
frame, but this encoder does not know about. But that's probably not a
huge deal.

-- 
Anton Khirnov
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