On Tue, Apr 24, 2018 at 01:59:26PM -0700, Aman Gupta wrote:
> From: Aman Gupta <a...@tmm1.net>
>
> This fixes issues reported on some devices where both
> avcodec_send_packet and avcodec_receive_frame can return EAGAIN
> at the same time, instead of one or the other blocking.
>
> 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().
> ---
> libavcodec/mediacodecdec.c | 78
> ++++++++++++++++++++-------------------
> libavcodec/mediacodecdec_common.c | 28 ++++++++------
> libavcodec/mediacodecdec_common.h | 4 +-
> 3 files changed, 59 insertions(+), 51 deletions(-)
>
> diff --git a/libavcodec/mediacodecdec.c b/libavcodec/mediacodecdec.c
> index e5d3e6a0af..1a681d771e 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 +405,52 @@ 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, wait a while 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;
> + }
> + 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);
If the input is starved on the FFmpeg side, we shouldn't block on trying
to receive a new frame from MediaCodec as it causes a performance
regression while the decoder is still not buffered enough to output its
first frame (after init or after a flush) as the function will end up
waiting 8ms for each new packet (for each call to avcodec_send_packet()).
Returning directly EAGAIN from here is fine as we will end up calling
ff_mediacodec_dec_receive() from the next call to avcodec_send_packet() or
avcodec_receive_frame().
With this modification the patch works fine on my devices without any
performance regression.
[...]
--
Matthieu B.
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