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Try to learn if decoders support retrying avcodec_receive_frame()

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This commit is contained in:
Cameron Gutman 2021-12-14 20:41:27 -06:00
parent 36e0468a99
commit 5a32992497
2 changed files with 43 additions and 2 deletions
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40
app/streaming/video/ffmpeg.cpp
View file

@ -46,6 +46,8 @@
#define FAILED_DECODES_RESET_THRESHOLD 20
#define MAX_RECV_FRAME_RETRIES 100
bool FFmpegVideoDecoder::isHardwareAccelerated()
{
return m_HwDecodeCfg != nullptr ||
@ -134,7 +136,8 @@ FFmpegVideoDecoder::FFmpegVideoDecoder(bool testOnly)
m_StreamFps(0),
m_VideoFormat(0),
m_NeedsSpsFixup(false),
m_TestOnly(testOnly)
m_TestOnly(testOnly),
m_CanRetryReceiveFrame(RRF_UNKNOWN)
{
SDL_zero(m_ActiveWndVideoStats);
SDL_zero(m_LastWndVideoStats);
@ -995,6 +998,11 @@ int FFmpegVideoDecoder::submitDecodeUnit(PDECODE_UNIT du)
// We can receive 0 or more frames after submission of a packet, so we must
// try to read until we get EAGAIN to ensure the queue is drained. Some decoders
// run asynchronously and may return several frames at once after warming up.
//
// Some decoders support calling avcodec_receive_frame() without queuing a packet.
// This allows us to drain excess frames and reduce latency. We will try to learn
// if a decoder is capable of this by trying it and seeing if it works.
int receiveRetries = 0;
do {
AVFrame* frame = av_frame_alloc();
if (!frame) {
@ -1036,11 +1044,39 @@ int FFmpegVideoDecoder::submitDecodeUnit(PDECODE_UNIT du)
// Queue the frame for rendering (or render now if pacer is disabled)
m_Pacer->submitFrame(frame);
submittedFrame = true;
// Once we receive a frame, transition out of the Unknown state by determining
// whether a receive frame retry was needed to get this frame. We assume that
// any asynchronous decoder is going to return EAGAIN on the first frame.
if (m_CanRetryReceiveFrame == RRF_UNKNOWN) {
SDL_LogInfo(SDL_LOG_CATEGORY_APPLICATION, "RRF mode: %s", receiveRetries > 0 ? "YES" : "NO");
m_CanRetryReceiveFrame = receiveRetries > 0 ? RRF_YES : RRF_NO;
}
}
else {
av_frame_free(&frame);
if (err == AVERROR(EAGAIN)) {
// Break out if we can't retry or we successfully received a frame. We only want
// to retry if we haven't gotten a frame back for this input packet.
if (m_CanRetryReceiveFrame == RRF_NO || receiveRetries == MAX_RECV_FRAME_RETRIES || submittedFrame) {
// We will transition from Unknown -> No if we exceed the maximum retries.
if (m_CanRetryReceiveFrame == RRF_UNKNOWN) {
SDL_assert(!submittedFrame);
SDL_assert(receiveRetries == MAX_RECV_FRAME_RETRIES);
SDL_LogWarn(SDL_LOG_CATEGORY_APPLICATION, "RRF mode: NO (timeout)");
m_CanRetryReceiveFrame = RRF_NO;
}
} while (err == 0);
break;
}
else {
SDL_Delay(1);
}
}
}
} while (err == 0 || (err == AVERROR(EAGAIN) && receiveRetries++ < MAX_RECV_FRAME_RETRIES));
// Treat this as a failed decode if we don't manage to receive a single frame or
// if we finish the loop above with an error other than EAGAIN. Note that some

5
app/streaming/video/ffmpeg.h
View file

@ -74,6 +74,11 @@ private:
int m_VideoFormat;
bool m_NeedsSpsFixup;
bool m_TestOnly;
enum {
RRF_UNKNOWN,
RRF_YES,
RRF_NO
} m_CanRetryReceiveFrame;
static const uint8_t k_H264TestFrame[];
static const uint8_t k_HEVCMainTestFrame[];