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// Copyright (C) 2021 The Qt Company Ltd.
// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR LGPL-3.0-only OR GPL-2.0-only OR GPL-3.0-only
#include "playbackengine/qffmpegdemuxer_p.h"
#include <QtCore/qloggingcategory.h>
#include <chrono>
QT_BEGIN_NAMESPACE
namespace QFFmpeg {
// 4 sec for buffering. TODO: maybe move to env var customization
static constexpr TrackDuration MaxBufferedDurationUs{ 4'000'000 };
// around 4 sec of hdr video
static constexpr qint64 MaxBufferedSize = 32 * 1024 * 1024;
Q_STATIC_LOGGING_CATEGORY(qLcDemuxer, "qt.multimedia.ffmpeg.demuxer");
static TrackPosition packetEndPos(const Packet &packet, const AVStream *stream,
const AVFormatContext *context)
{
const AVPacket &avPacket = *packet.avPacket();
return packet.loopOffset().loopStartTimeUs.asDuration()
+ toTrackPosition(AVStreamPosition(avPacket.pts + avPacket.duration), stream, context);
}
static bool isPacketWithinStreamDuration(const AVFormatContext *context, const Packet &packet)
{
const AVPacket &avPacket = *packet.avPacket();
const AVStream &avStream = *context->streams[avPacket.stream_index];
const AVStreamDuration streamDuration(avStream.duration);
if (streamDuration.get() <= 0
|| context->duration_estimation_method != AVFMT_DURATION_FROM_STREAM)
return true; // Stream duration shouldn't or doesn't need to be compared to pts
if (avPacket.pts == AV_NOPTS_VALUE) { // Unexpected situation
qWarning() << "QFFmpeg::Demuxer received AVPacket with pts == AV_NOPTS_VALUE";
return true;
}
if (avStream.start_time != AV_NOPTS_VALUE)
return AVStreamDuration(avPacket.pts - avStream.start_time) <= streamDuration;
const TrackPosition trackPos = toTrackPosition(AVStreamPosition(avPacket.pts), &avStream, context);
const TrackPosition trackPosOfStreamEnd = toTrackDuration(streamDuration, &avStream).asTimePoint();
return trackPos <= trackPosOfStreamEnd;
// TODO: If there is a packet that starts before the canonical end of the stream but has a
// malformed duration, rework doNextStep to check for eof after that packet.
}
Demuxer::Demuxer(const PlaybackEngineObjectID &id, AVFormatContext *context,
TrackPosition initialPosUs, bool seekPending, const LoopOffset &loopOffset,
const StreamIndexes &streamIndexes, int loops)
: PlaybackEngineObject(id),
m_context(context),
m_sessionCtx{ initialPosUs, loopOffset, !seekPending && initialPosUs == TrackPosition{ 0 } },
m_loops(loops)
{
qCDebug(qLcDemuxer) << "Create demuxer."
<< "pos:" << m_sessionCtx.posInLoopUs.get()
<< "loop offset:" << m_sessionCtx.loopOffset.loopStartTimeUs.get()
<< "loop index:" << m_sessionCtx.loopOffset.loopIndex << "loops:" << loops;
Q_ASSERT(m_context);
for (size_t i = 0; i < QPlatformMediaPlayer::NTrackTypes; ++i) {
if (streamIndexes[i] >= 0) {
const auto trackType = static_cast<TrackType>(i);
qCDebug(qLcDemuxer) << "Activate demuxing stream" << i << ", trackType:" << trackType;
m_streams[streamIndexes[i]] = { trackType };
}
}
}
void Demuxer::seek(quint64 sessionId, TrackPosition initialPosUs, const LoopOffset &loopOffset)
{
updateSession(sessionId, [this, initialPosUs, loopOffset]() {
m_sessionCtx = { initialPosUs, loopOffset };
for (auto &[id, streamData] : m_streams)
streamData = StreamData{ streamData.trackType };
scheduleNextStep();
});
}
void Demuxer::doNextStep()
{
ensureSeeked();
Packet packet(m_sessionCtx.loopOffset, AVPacketUPtr{ av_packet_alloc() }, id());
AVPacket &avPacket = *packet.avPacket();
const int demuxStatus = av_read_frame(m_context, &avPacket);
if (demuxStatus == AVERROR_EXIT)
return;
const int streamIndex = avPacket.stream_index;
auto streamIterator = m_streams.find(streamIndex);
const bool streamIsRelevant = streamIterator != m_streams.end();
if (demuxStatus == AVERROR_EOF
|| (streamIsRelevant && !isPacketWithinStreamDuration(m_context, packet))) {
++m_sessionCtx.loopOffset.loopIndex;
const auto loops = m_loops.loadAcquire();
if (loops >= 0 && m_sessionCtx.loopOffset.loopIndex >= loops) {
qCDebug(qLcDemuxer) << "finish demuxing";
if (!std::exchange(m_sessionCtx.buffered, true))
Q_EMIT packetsBuffered();
setAtEnd(true);
} else {
// start next loop
m_sessionCtx.seeked = false;
m_sessionCtx.posInLoopUs = TrackPosition(0);
m_sessionCtx.loopOffset.loopStartTimeUs = m_sessionCtx.maxPacketsEndPos;
m_sessionCtx.maxPacketsEndPos = TrackPosition(0);
ensureSeeked();
qCDebug(qLcDemuxer) << "Demuxer loops changed. Index:"
<< m_sessionCtx.loopOffset.loopIndex
<< "Offset:" << m_sessionCtx.loopOffset.loopStartTimeUs.get();
scheduleNextStep();
}
return;
}
if (demuxStatus < 0) {
qCWarning(qLcDemuxer) << "Demuxing failed" << demuxStatus << AVError(demuxStatus);
if (demuxStatus == AVERROR(EAGAIN)
&& m_sessionCtx.demuxerRetryCount != s_maxDemuxerRetries) {
// When demuxer reports EAGAIN, we can try to recover by calling av_read_frame again.
// The documentation for av_read_frame does not mention this, but FFmpeg command line
// tool does this, see input_thread() function in ffmpeg_demux.c. There, the response
// is to sleep for 10 ms before trying again. NOTE: We do not have any known way of
// reproducing this in our tests.
m_sessionCtx.failTimePoint = std::chrono::steady_clock::now();
++m_sessionCtx.demuxerRetryCount;
qCDebug(qLcDemuxer) << "Retrying";
scheduleNextStep();
} else {
// av_read_frame reports another error. This could for example happen if network is
// disconnected while playing a network stream, where av_read_frame may return
// ETIMEDOUT.
// TODO: Demuxer errors should likely stop playback in media player examples.
Q_EMIT error(QMediaPlayer::ResourceError,
QLatin1StringView("Demuxing failed"));
}
return;
}
m_sessionCtx.demuxerRetryCount = 0;
m_sessionCtx.failTimePoint.reset();
if (streamIsRelevant) {
auto &streamData = streamIterator->second;
const AVStream *stream = m_context->streams[streamIndex];
const TrackPosition endPos = packetEndPos(packet, stream, m_context);
m_sessionCtx.maxPacketsEndPos = qMax(m_sessionCtx.maxPacketsEndPos, endPos);
// Increase buffered metrics as the packet has been processed.
streamData.bufferedDuration += toTrackDuration(AVStreamDuration(avPacket.duration), stream);
streamData.bufferedSize += avPacket.size;
streamData.maxSentPacketsPos = qMax(streamData.maxSentPacketsPos, endPos);
updateStreamDataLimitFlag(streamData);
if (!m_sessionCtx.buffered && streamData.isDataLimitReached) {
m_sessionCtx.buffered = true;
Q_EMIT packetsBuffered();
}
if (!m_sessionCtx.firstPacketFound) {
m_sessionCtx.firstPacketFound = true;
Q_EMIT firstPacketFound(id(),
m_sessionCtx.posInLoopUs
+ m_sessionCtx.loopOffset.loopStartTimeUs.asDuration());
}
auto signal = signalByTrackType(streamData.trackType);
Q_EMIT (this->*signal)(std::move(packet));
}
scheduleNextStep();
}
void Demuxer::onPacketProcessed(const Packet &packet)
{
Q_ASSERT(packet.isValid());
if (!checkID(packet.sourceID()))
return;
auto &avPacket = *packet.avPacket();
const auto streamIndex = avPacket.stream_index;
const auto stream = m_context->streams[streamIndex];
auto it = m_streams.find(streamIndex);
if (it != m_streams.end()) {
auto &streamData = it->second;
// Decrease buffered metrics as new data (the packet) has been received (buffered)
streamData.bufferedDuration -= toTrackDuration(AVStreamDuration(avPacket.duration), stream);
streamData.bufferedSize -= avPacket.size;
streamData.maxProcessedPacketPos =
qMax(streamData.maxProcessedPacketPos, packetEndPos(packet, stream, m_context));
Q_ASSERT(it->second.bufferedDuration >= TrackDuration(0));
Q_ASSERT(it->second.bufferedSize >= 0);
updateStreamDataLimitFlag(streamData);
}
scheduleNextStep();
}
Demuxer::TimePoint Demuxer::nextTimePoint() const
{
Q_ASSERT(m_sessionCtx.failTimePoint.has_value() == !!m_sessionCtx.demuxerRetryCount);
return m_sessionCtx.failTimePoint ? *m_sessionCtx.failTimePoint + s_demuxerRetryInterval
: PlaybackEngineObject::nextTimePoint();
}
bool Demuxer::canDoNextStep() const
{
auto isDataLimitReached = [](const auto &streamIndexToData) {
return streamIndexToData.second.isDataLimitReached;
};
// Demuxer waits:
// - if it's paused
// - if the end has been reached
// - if streams are empty (probably, should be handled on the initialization)
// - if at least one of the streams has reached the data limit (duration or size)
return PlaybackEngineObject::canDoNextStep() && !isAtEnd() && !m_streams.empty()
&& std::none_of(m_streams.begin(), m_streams.end(), isDataLimitReached);
}
void Demuxer::ensureSeeked()
{
if (std::exchange(m_sessionCtx.seeked, true))
return;
if ((m_context->ctx_flags & AVFMTCTX_UNSEEKABLE) == 0) {
// m_posInLoopUs is intended to be the number of microseconds since playback start, and is
// in the range [0, duration()]. av_seek_frame seeks to a position relative to the start of
// the media timeline, which may be non-zero. We adjust for this by adding the
// AVFormatContext's start_time.
//
// NOTE: m_posInLoop is not calculated correctly if the start_time is non-zero, but
// this must be fixed separately.
const AVContextPosition seekPos = toContextPosition(m_sessionCtx.posInLoopUs, m_context);
qCDebug(qLcDemuxer).nospace()
<< "Seeking to offset " << m_sessionCtx.posInLoopUs.get() << "us from media start.";
auto err = av_seek_frame(m_context, -1, seekPos.get(), AVSEEK_FLAG_BACKWARD);
if (err < 0) {
qCWarning(qLcDemuxer) << "Failed to seek, pos" << seekPos.get();
// Drop an error of seeking to initial position of streams with undefined duration.
// This needs improvements.
if (m_sessionCtx.posInLoopUs != TrackPosition{ 0 } || m_context->duration > 0)
Q_EMIT error(QMediaPlayer::ResourceError,
QLatin1StringView("Failed to seek: ") + err2str(err));
}
}
setAtEnd(false);
}
Demuxer::RequestingSignal Demuxer::signalByTrackType(TrackType trackType)
{
switch (trackType) {
case TrackType::VideoStream:
return &Demuxer::requestProcessVideoPacket;
case TrackType::AudioStream:
return &Demuxer::requestProcessAudioPacket;
case TrackType::SubtitleStream:
return &Demuxer::requestProcessSubtitlePacket;
default:
Q_ASSERT(!"Unknown track type");
}
return nullptr;
}
void Demuxer::setLoops(int loopsCount)
{
qCDebug(qLcDemuxer) << "setLoops to demuxer" << loopsCount;
m_loops.storeRelease(loopsCount);
}
void Demuxer::updateStreamDataLimitFlag(StreamData &streamData)
{
const TrackDuration packetsPosDiff =
streamData.maxSentPacketsPos - streamData.maxProcessedPacketPos;
streamData.isDataLimitReached = streamData.bufferedDuration >= MaxBufferedDurationUs
|| (streamData.bufferedDuration == TrackDuration(0)
&& packetsPosDiff >= MaxBufferedDurationUs)
|| streamData.bufferedSize >= MaxBufferedSize;
}
} // namespace QFFmpeg
QT_END_NAMESPACE
#include "moc_qffmpegdemuxer_p.cpp"