[FFmpeg-devel] [PATCH v2 2/4] avcodec/mediacodecdec: restructure mediacodec_receive_frame

[Matthieu Bouron]

On Thu, May 03, 2018 at 10:24:49AM -0700, Aman Gupta wrote:
> On Thu, May 3, 2018 at 12:33 AM, Matthieu Bouron <matthieu.bouron at gmail.com>
> wrote:
> 
> > On Wed, May 02, 2018 at 07:24:58PM -0700, Aman Gupta wrote:
> > > From: Aman Gupta <aman at tmm1.net>
> > >
> > > The new logic follows a recommendation by @rcombs to use
> > > dequeueInputBuffer with a timeout of 0 as a way to detect
> > > whether the codec wants more data. The dequeued buffer index is
> > > kept in MediaCodecDecContext until it can be used next.
> > >
> > > A similar technique is also used by the Google's official media
> > > player Exoplayer: see MediaCodecRenderer.feedInputBuffer().
> > >
> > > Signed-off-by: Aman Gupta <aman at tmm1.net>
> > > ---
> > >  libavcodec/mediacodecdec.c        | 80 ++++++++++++++++++++----------
> > ---------
> > >  libavcodec/mediacodecdec_common.c | 28 ++++++++------
> > >  libavcodec/mediacodecdec_common.h |  4 +-
> > >  3 files changed, 61 insertions(+), 51 deletions(-)
> > >
> > > diff --git a/libavcodec/mediacodecdec.c b/libavcodec/mediacodecdec.c
> > > index 86ceee5a83..2ac22dd1f6 100644
> > > --- a/libavcodec/mediacodecdec.c
> > > +++ b/libavcodec/mediacodecdec.c
> > > @@ -391,33 +391,11 @@ done:
> > >      return ret;
> > >  }
> > >
> > > -static int mediacodec_send_receive(AVCodecContext *avctx,
> > > -                                   MediaCodecH264DecContext *s,
> > > -                                   AVFrame *frame, bool wait)
> > > -{
> > > -    int ret;
> > > -
> > > -    /* send any pending data from buffered packet */
> > > -    while (s->buffered_pkt.size) {
> > > -        ret = ff_mediacodec_dec_send(avctx, s->ctx, &s->buffered_pkt);
> > > -        if (ret == AVERROR(EAGAIN))
> > > -            break;
> > > -        else if (ret < 0)
> > > -            return ret;
> > > -        s->buffered_pkt.size -= ret;
> > > -        s->buffered_pkt.data += ret;
> > > -        if (s->buffered_pkt.size <= 0)
> > > -            av_packet_unref(&s->buffered_pkt);
> > > -    }
> > > -
> > > -    /* check for new frame */
> > > -    return ff_mediacodec_dec_receive(avctx, s->ctx, frame, wait);
> > > -}
> > > -
> > >  static int mediacodec_receive_frame(AVCodecContext *avctx, AVFrame
> > *frame)
> > >  {
> > >      MediaCodecH264DecContext *s = avctx->priv_data;
> > >      int ret;
> > > +    ssize_t index;
> > >
> > >      /* In delay_flush mode, wait until the user has released or rendered
> > >         all retained frames. */
> > > @@ -427,28 +405,54 @@ static int mediacodec_receive_frame(AVCodecContext
> > *avctx, AVFrame *frame)
> > >          }
> > >      }
> > >
> > > -    /* flush buffered packet and check for new frame */
> > > -    ret = mediacodec_send_receive(avctx, s, frame, false);
> > > +    /* poll for new frame */
> > > +    ret = ff_mediacodec_dec_receive(avctx, s->ctx, frame, false);
> > >      if (ret != AVERROR(EAGAIN))
> > >          return ret;
> > >
> > > -    /* skip fetching new packet if we still have one buffered */
> > > -    if (s->buffered_pkt.size > 0)
> > > -        return mediacodec_send_receive(avctx, s, frame, true);
> > > +    /* feed decoder */
> > > +    while (1) {
> > > +        if (s->ctx->current_input_buffer < 0) {
> > > +            /* poll for input space */
> > > +            index = ff_AMediaCodec_dequeueInputBuffer(s->ctx->codec,
> > 0);
> > > +            if (index < 0) {
> > > +                /* no space, block for an output frame to appear */
> > > +                return ff_mediacodec_dec_receive(avctx, s->ctx, frame,
> > true);
> > > +            }
> > > +            s->ctx->current_input_buffer = index;
> > > +        }
> > >
> > > -    /* fetch new packet or eof */
> > > -    ret = ff_decode_get_packet(avctx, &s->buffered_pkt);
> > > -    if (ret == AVERROR_EOF) {
> > > -        AVPacket null_pkt = { 0 };
> > > -        ret = ff_mediacodec_dec_send(avctx, s->ctx, &null_pkt);
> > > -        if (ret < 0)
> > > +        /* try to flush any buffered packet data */
> > > +        if (s->buffered_pkt.size > 0) {
> > > +            ret = ff_mediacodec_dec_send(avctx, s->ctx,
> > &s->buffered_pkt, false);
> > > +            if (ret >= 0) {
> > > +                s->buffered_pkt.size -= ret;
> > > +                s->buffered_pkt.data += ret;
> > > +                if (s->buffered_pkt.size <= 0)
> > > +                    av_packet_unref(&s->buffered_pkt);
> > > +            } else if (ret < 0 && ret != AVERROR(EAGAIN)) {
> > > +                return ret;
> > > +            }
> > > +
> > > +            /* poll for space again */
> > > +            continue;
> > > +        }
> > > +
> > > +        /* fetch new packet or eof */
> > > +        ret = ff_decode_get_packet(avctx, &s->buffered_pkt);
> > > +        if (ret == AVERROR_EOF) {
> > > +            AVPacket null_pkt = { 0 };
> > > +            ret = ff_mediacodec_dec_send(avctx, s->ctx, &null_pkt,
> > true);
> > > +            if (ret < 0)
> > > +                return ret;
> > > +        } else if (ret == AVERROR(EAGAIN) &&
> > s->ctx->current_input_buffer < 0) {
> > > +            return ff_mediacodec_dec_receive(avctx, s->ctx, frame,
> > true);
> > > +        } else if (ret < 0) {
> > >              return ret;
> > > +        }
> >
> > Same comment as for the previous version of the patch:
> > https://ffmpeg.org/pipermail/ffmpeg-devel/2018-April/228978.html
> 
> 
> I think that comment has been addressed in this version of the patch. The
> wait here only happens if current_input_buffer is not available,
> meaning that the decoder is not accepting new packets. If there is space
> for new input packets, the wait will not happen.
> 
> I think the bug in the version you tested (presumably from my GH fork) was
> the missing "poll for space again" continue above.

Sorry, I re-did some test on my devices and the issue has been addressed
with this patch. So, LGTM.

[...]

-- 
Matthieu B.