On Sat, 11. Apr 15:56, Mark Thompson wrote:
> On 04/04/2020 21:26, Andriy Gelman wrote:
> > From: Andriy Gelman <andriy.gel...@gmail.com>
> >
> > The dequeued packets from vp8 (s5p-mfc) encoder are output in ivf format
> > which breaks the stream when the packets are muxed in avformat. This commit
> > adds an option to remove the container and thus support the encoder.
> >
> > Signed-off-by: Andriy Gelman <andriy.gel...@gmail.com>
> > ---
> > libavcodec/v4l2_m2m.h | 2 ++
> > libavcodec/v4l2_m2m_enc.c | 53 +++++++++++++++++++++++++++++++--------
> > 2 files changed, 45 insertions(+), 10 deletions(-)
> >
> > diff --git a/libavcodec/v4l2_m2m.h b/libavcodec/v4l2_m2m.h
> > index 456281f48c..525f9456e9 100644
> > --- a/libavcodec/v4l2_m2m.h
> > +++ b/libavcodec/v4l2_m2m.h
> > @@ -73,6 +73,8 @@ typedef struct V4L2m2mPriv {
> >
> > int num_output_buffers;
> > int num_capture_buffers;
> > + int strip_ivf;
> > + int ivf_detected;
> > } V4L2m2mPriv;
> >
> > /**
> > diff --git a/libavcodec/v4l2_m2m_enc.c b/libavcodec/v4l2_m2m_enc.c
> > index c9f1741bfd..9c11f90567 100644
> > --- a/libavcodec/v4l2_m2m_enc.c
> > +++ b/libavcodec/v4l2_m2m_enc.c
> > @@ -25,6 +25,8 @@
> > #include <sys/ioctl.h>
> > #include <search.h>
> > #include "libavcodec/avcodec.h"
> > +#include "libavcodec/internal.h"
> > +#include "libavutil/intreadwrite.h"
> > #include "libavutil/pixdesc.h"
> > #include "libavutil/pixfmt.h"
> > #include "libavutil/opt.h"
> > @@ -256,6 +258,7 @@ static int v4l2_send_frame(AVCodecContext *avctx, const
> > AVFrame *frame)
> >
> > static int v4l2_receive_packet(AVCodecContext *avctx, AVPacket *avpkt)
> > {
> > + V4L2m2mPriv *priv = avctx->priv_data;
> > V4L2m2mContext *s = ((V4L2m2mPriv*)avctx->priv_data)->context;
> > V4L2Context *const capture = &s->capture;
> > V4L2Context *const output = &s->output;
> > @@ -281,7 +284,28 @@ static int v4l2_receive_packet(AVCodecContext *avctx,
> > AVPacket *avpkt)
> > }
> >
> > dequeue:
> > - return ff_v4l2_context_dequeue_packet(capture, avpkt);
> > + ret = ff_v4l2_context_dequeue_packet(capture, avpkt);
> > + if (ret)
> > + return ret;
> > +
> > + if (priv->strip_ivf) {
> > + int header_offset = 0;
> > + if (avpkt->size >= 32 && AV_RL32(avpkt->data) ==
> > MKTAG('D','K','I','F')) {
> > + header_offset = 32;
> > + priv->ivf_detected = 1;
> > + } else if (priv->ivf_detected) {
> > + header_offset = 12;
> > + }
> > + header_offset = FFMIN(header_offset, avpkt->size);
> > + avpkt->data += header_offset;
> > + avpkt->size -= header_offset;
> > +
> > + if (avpkt->size == 0) {
>
> Does this case ever happen? Wouldn't something have gone very wrong here to
> get here?
It happens on the first packet, when the dequeued packet only contains the
32byte ivf header.
Also when draining (not related to this patch), avpkt->size == 0 indicates that
all the capture buffers are flushed.
>
> > + av_packet_unref(avpkt);
> > + goto dequeue;
> > + }
> > + }
> > + return 0;
> > }
>
> Could the presence of the IVF container be autodetected? I suspect it can,
> because the tag will collide with the fixed start code in the intra frame at
> the start of the stream. If that were possible then it would avoid having
> the tricky option which users are not going to easily know about.
I think it can. Will test this approach.
>
> Otherwise seems ok. It's rather horrible, but it looks like the best
> solution to the problem.
I agree it's quite ugly. I'll look into whether auto inserted bsf can be
extended to encoders.
Thanks,
--
Andriy
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