MMAL is an fundamentally an asynchronous decoder, which was a bad fit
for the legacy dataflow API. Often multiple packets are enqueued before
a flood of frames are returned from MMAL.
The previous lockstep dataflow meant that any delay in returning packets
from the VPU would cause ctx->queue_decoded_frames to grow with no way
of draining the queue.
Testing this with mpv streaming from a live RTSP source visibly reduced
latency introduced by frames waiting in queue_decoded_frames from
roughly 2s to 0.
Signed-off-by: Ho Ming Shun <cyph1...@gmail.com>
---
libavcodec/mmaldec.c | 28 +++++++++++++++++++++-------
1 file changed, 21 insertions(+), 7 deletions(-)
diff --git a/libavcodec/mmaldec.c b/libavcodec/mmaldec.c
index 03e15420ce..b97cc6ff5e 100644
--- a/libavcodec/mmaldec.c
+++ b/libavcodec/mmaldec.c
@@ -578,6 +578,7 @@ static int ffmmal_add_packet(AVCodecContext *avctx,
AVPacket *avpkt,
done:
av_buffer_unref(&buf);
+ av_packet_unref(avpkt);
return ret;
}
@@ -663,6 +664,12 @@ static int ffmal_copy_frame(AVCodecContext *avctx,
AVFrame *frame,
avctx->pix_fmt, avctx->width, avctx->height);
}
+ frame->sample_aspect_ratio = avctx->sample_aspect_ratio;
+ frame->width = avctx->width;
+ frame->width = avctx->width;
+ frame->height = avctx->height;
+ frame->format = avctx->pix_fmt;
+
frame->pts = buffer->pts == MMAL_TIME_UNKNOWN ? AV_NOPTS_VALUE :
buffer->pts;
#if FF_API_PKT_PTS
FF_DISABLE_DEPRECATION_WARNINGS
@@ -776,12 +783,12 @@ done:
return ret;
}
-static int ffmmal_decode(AVCodecContext *avctx, void *data, int *got_frame,
- AVPacket *avpkt)
+static int ffmmal_receive_frame(AVCodecContext *avctx, AVFrame *frame)
{
MMALDecodeContext *ctx = avctx->priv_data;
- AVFrame *frame = data;
+ AVPacket avpkt = {0};
int ret = 0;
+ int got_frame = 0;
if (avctx->extradata_size && !ctx->extradata_sent) {
AVPacket pkt = {0};
@@ -793,7 +800,11 @@ static int ffmmal_decode(AVCodecContext *avctx, void
*data, int *got_frame,
return ret;
}
- if ((ret = ffmmal_add_packet(avctx, avpkt, 0)) < 0)
+ ret = ff_decode_get_packet(avctx, &avpkt);
+ if(ret == 0) {
+ if ((ret = ffmmal_add_packet(avctx, &avpkt, 0)) < 0)
+ return ret;
+ } else if(ret < 0 && !(ret == AVERROR(EAGAIN)))
return ret;
if ((ret = ffmmal_fill_input_port(avctx)) < 0)
@@ -802,7 +813,7 @@ static int ffmmal_decode(AVCodecContext *avctx, void *data,
int *got_frame,
if ((ret = ffmmal_fill_output_port(avctx)) < 0)
return ret;
- if ((ret = ffmmal_read_frame(avctx, frame, got_frame)) < 0)
+ if ((ret = ffmmal_read_frame(avctx, frame, &got_frame)) < 0)
return ret;
// ffmmal_read_frame() can block for a while. Since the decoder is
@@ -814,7 +825,10 @@ static int ffmmal_decode(AVCodecContext *avctx, void
*data, int *got_frame,
if ((ret = ffmmal_fill_input_port(avctx)) < 0)
return ret;
- return ret;
+ if(!got_frame && ret == 0)
+ return AVERROR(EAGAIN);
+ else
+ return ret;
}
static const AVCodecHWConfigInternal *const mmal_hw_configs[] = {
@@ -846,7 +860,7 @@ static const AVOption options[]={
.priv_data_size = sizeof(MMALDecodeContext), \
.init = ffmmal_init_decoder, \
.close = ffmmal_close_decoder, \
- .decode = ffmmal_decode, \
+ .receive_frame = ffmmal_receive_frame, \
.flush = ffmmal_flush, \
.priv_class = &ffmmal_##NAME##_dec_class, \
.capabilities = AV_CODEC_CAP_DELAY | AV_CODEC_CAP_HARDWARE, \
--
2.33.0
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