qffmpegvideoframeencoder.cpp

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// Copyright (C) 2022 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 "qffmpegvideoframeencoder_p.h"
#include "qffmpegmediaformatinfo_p.h"
#include "qffmpegencoderoptions_p.h"
#include "qffmpegvideoencoderutils_p.h"
#include "qffmpegcodecstorage_p.h"
#include "qffmpegrecordingengineutils_p.h"
 
#include <QtCore/qloggingcategory.h>
#include <QtCore/private/qexpected_p.h>
 
extern "C" {
#include "libavutil/display.h"
#include "libavutil/pixdesc.h"
}
 
QT_BEGIN_NAMESPACE
 
namespace ranges = QtMultimediaPrivate::ranges;
 
Q_STATIC_LOGGING_CATEGORY(qLcVideoFrameEncoder, "qt.multimedia.ffmpeg.videoencoder");
 
namespace QFFmpeg {
 
namespace {
 
AVCodecID avCodecID(const QMediaEncoderSettings &settings)
{
    const QMediaFormat::VideoCodec qVideoCodec = settings.videoCodec();
    return QFFmpegMediaFormatInfo::codecIdForVideoCodec(qVideoCodec);
}
 
// LATER: move to HWAccel or Codec?
std::optional<AVHWDeviceType> getHwDeviceType(const Codec &codec)
{
    std::optional<AVPixelFormat> pixelFormat = findAVPixelFormat(codec, isHwPixelFormat);
    if (!pixelFormat)
        return std::nullopt;
 
    const AVCodecHWConfig *cfg = codec.hwConfigForPixelFormat(*pixelFormat);
    if (!cfg)
        return std::nullopt;
 
    bool supportsHwDeviceContext = (cfg->methods & AV_CODEC_HW_CONFIG_METHOD_HW_DEVICE_CTX) != 0;
    bool supportsHwFramesContext = (cfg->methods & AV_CODEC_HW_CONFIG_METHOD_HW_FRAMES_CTX) != 0;
    if (!supportsHwDeviceContext && !supportsHwFramesContext)
        return std::nullopt;
 
    const QSpan deviceTypes = HWAccel::encodingDeviceTypes();
    auto found = ranges::find_if(deviceTypes, [&](AVHWDeviceType deviceType) {
        return pixelFormatForHwDevice(deviceType) == pixelFormat;
    });
    if (found != deviceTypes.end())
        return *found;
    else
        return std::nullopt;
}
 
bool muxerNeedsGlobalHeader(const AVFormatContext *formatContext)
{
    return (formatContext->oformat->flags & AVFMT_GLOBALHEADER) != 0;
}
 
} // namespace
 
VideoFrameEncoderUPtr VideoFrameEncoder::create(const QMediaEncoderSettings &encoderSettings,
                                                const SourceParams &sourceParams,
                                                AVFormatContext *formatContext)
{
    Q_ASSERT(isSwPixelFormat(sourceParams.swFormat));
    Q_ASSERT(isHwPixelFormat(sourceParams.format) || sourceParams.swFormat == sourceParams.format);
 
    AVStream *stream = createStream(sourceParams, formatContext);
    if (!stream)
        return nullptr;
 
    const AVCodecID codecId = avCodecID(encoderSettings);
    const bool needsGlobalHeader = muxerNeedsGlobalHeader(formatContext);
 
    // first we try to open a hardware encoder
    VideoFrameEncoderUPtr encoder = [&]() -> VideoFrameEncoderUPtr {
        const std::vector encoders = findAndScoreEncoders(codecId, [](const Codec &codec) {
            std::optional<AVHWDeviceType> deviceType = getHwDeviceType(codec);
            if (!deviceType)
                return NotSuitableAVScore;
 
            const QSpan deviceTypes = HWAccel::encodingDeviceTypes();
            auto found = ranges::find(deviceTypes, *deviceType);
            Q_ASSERT(found != deviceTypes.end());
 
            return DefaultAVScore - static_cast<AVScore>(found - deviceTypes.begin());
        });
 
        for (const auto &[codec, score] : encoders) {
            HWAccelUPtr hwAccel = HWAccel::create(*getHwDeviceType(codec));
            if (!hwAccel)
                continue;
            if (!hwAccel->matchesSizeContraints(encoderSettings.videoResolution()))
                continue;
            auto encoder = create(stream, codec, std::move(hwAccel), sourceParams, encoderSettings,
                                  needsGlobalHeader);
            if (encoder)
                return encoder;
        }
        return nullptr;
    }();
 
    if (!encoder) {
        // otherwise fall back to software
        encoder = [&]() -> VideoFrameEncoderUPtr {
            const std::vector encoders = findAndScoreEncoders(codecId, [&](const Codec &codec) {
                const QSize resolution = adjustVideoResolution(codec, encoderSettings.videoResolution());
                return findSWFormatScores(codec, sourceParams.swFormat, resolution);
            });
 
            for (const auto &[codec, score] : encoders) {
                auto encoder = create(stream, codec, nullptr, sourceParams, encoderSettings,
                                      needsGlobalHeader);
                if (encoder)
                    return encoder;
            }
            return nullptr;
        }();
    }
 
    if (encoder)
        qCDebug(qLcVideoFrameEncoder)
                << "found" << (encoder->m_accel ? "hw" : "sw") << "encoder"
                << encoder->m_codec.name() << "for id" << encoder->m_codec.id();
    else
        qCWarning(qLcVideoFrameEncoder) << "No valid video codecs found";
 
    return encoder;
}
 
static AVPixelFormat inferHardwareFormat(AVPixelFormat sourceSwFormat, const Codec &codec,
                                         HWAccel *accel, QSize targetSize)
{
    const std::optional format = findTargetFormat(sourceSwFormat, codec, accel, targetSize);
    if (!format)
        qWarning() << "Could not find target format for codecId" << codec.id();
 
    return format.value_or(AV_PIX_FMT_NONE);
}
 
static QSize computeTargetSize(const Codec &codec, const QMediaEncoderSettings &settings)
{
    QSize targetSize = adjustVideoResolution(codec, settings.videoResolution());
 
#ifdef Q_OS_WINDOWS
    // TODO: investigate, there might be more encoders not supporting odd resolution
    if (codec.name() == u"h264_mf") {
        auto makeEven = [](int size) { return size & ~1; };
        const QSize fixedSize(makeEven(targetSize.width()), makeEven(targetSize.height()));
        if (fixedSize != targetSize) {
            qCDebug(qLcVideoFrameEncoder) << "Fix odd video resolution for codec" << codec.name()
                                          << ":" << targetSize << "->" << fixedSize;
            targetSize = fixedSize;
        }
    }
#endif
 
    return targetSize;
}
 
VideoFrameEncoder::VideoFrameEncoder(AVStream *stream, const Codec &codec, HWAccelUPtr hwAccel,
                                     const SourceParams &sourceParams,
                                     const QMediaEncoderSettings &encoderSettings,
                                     bool needsGlobalHeader)
    : m_settings(encoderSettings),
      m_stream(stream),
      m_codec(codec),
      m_accel(std::move(hwAccel)),
      m_needsGlobalHeader(needsGlobalHeader),
      m_sourceSize(sourceParams.size),
      m_targetSize(computeTargetSize(codec, encoderSettings)),
      m_sourceFormat(sourceParams.format),
      m_sourceSWFormat(sourceParams.swFormat),
      m_targetFormat(inferHardwareFormat(sourceParams.swFormat, codec, m_accel.get(), m_targetSize)),
      m_sourceFrameRate(sourceParams.frameRate)
{
    initCodecFrameRate();
    initStream();
}
 
AVStream *VideoFrameEncoder::createStream(const SourceParams &sourceParams,
                                          AVFormatContext *formatContext)
{
    AVStream *stream = avformat_new_stream(formatContext, nullptr);
 
    if (!stream)
        return stream;
 
    stream->id = formatContext->nb_streams - 1;
    stream->codecpar->codec_type = AVMEDIA_TYPE_VIDEO;
 
    stream->codecpar->color_trc = sourceParams.colorTransfer;
    stream->codecpar->color_space = sourceParams.colorSpace;
    stream->codecpar->color_range = sourceParams.colorRange;
 
    if (sourceParams.transform.rotation != QtVideo::Rotation::None || sourceParams.transform.mirroredHorizontallyAfterRotation) {
        constexpr auto displayMatrixSize = sizeof(int32_t) * 9;
        AVPacketSideData sideData = { reinterpret_cast<uint8_t *>(av_malloc(displayMatrixSize)),
                                      displayMatrixSize, AV_PKT_DATA_DISPLAYMATRIX };
        int32_t *matrix = reinterpret_cast<int32_t *>(sideData.data);
        av_display_rotation_set(matrix, static_cast<double>(sourceParams.transform.rotation));
        if (sourceParams.transform.mirroredHorizontallyAfterRotation)
            av_display_matrix_flip(matrix, sourceParams.transform.mirroredHorizontallyAfterRotation, false);
 
        addStreamSideData(stream, sideData);
    }
 
    return stream;
}
 
VideoFrameEncoderUPtr VideoFrameEncoder::create(AVStream *stream, const Codec &codec,
                                                HWAccelUPtr hwAccel,
                                                const SourceParams &sourceParams,
                                                const QMediaEncoderSettings &encoderSettings,
                                                bool needsGlobalHeader)
{
    VideoFrameEncoderUPtr frameEncoder(new VideoFrameEncoder(stream, codec, std::move(hwAccel),
                                                             sourceParams, encoderSettings,
                                                             needsGlobalHeader));
 
    if (frameEncoder->targetFormat() == AV_PIX_FMT_NONE)
        return {};
 
    auto targetSwFormats = frameEncoder->enumerateTargetSwFormats();
 
    for (ScoredPixelFormat candidate : targetSwFormats) {
        if (frameEncoder->tryInitTargetSwFormat(candidate.format)) {
            qCDebug(qLcVideoFrameEncoder) << "Selected target sw format" << candidate.format
                                          << "for codec" << frameEncoder->m_codec.name();
            return frameEncoder;
        }
        qCDebug(qLcVideoFrameEncoder) << "Failed to init target sw format" << candidate.format
                                      << "for codec" << frameEncoder->m_codec.name();
    }
 
    return nullptr;
}
 
void VideoFrameEncoder::initCodecFrameRate()
{
    const auto frameRates = m_codec.frameRates();
    if (qLcVideoFrameEncoder().isEnabled(QtDebugMsg))
        for (AVRational rate : frameRates)
            qCDebug(qLcVideoFrameEncoder) << "supported frame rate:" << rate;
 
    m_codecFrameRate = adjustFrameRate(frameRates, m_settings.videoFrameRate(), m_sourceFrameRate);
    qCDebug(qLcVideoFrameEncoder) << "Adjusted frame rate:" << m_codecFrameRate;
}
 
std::vector<ScoredPixelFormat> VideoFrameEncoder::enumerateTargetSwFormats() const
{
    return QFFmpeg::findAndScoreTargetSWFormats(m_sourceSWFormat, m_codec, m_accel.get(),
                                                m_targetSize);
}
 
bool VideoFrameEncoder::tryInitTargetSwFormat(AVPixelFormat targetSwFormat)
{
    qCDebug(qLcVideoFrameEncoder) << "Trying to init target sw format" << m_targetFormat
                                  << targetSwFormat;
 
    m_targetSWFormat = targetSwFormat;
    if (m_accel) {
        m_accel->destroyFramesContext();
        m_accel->createFramesContext(m_targetSWFormat, m_targetSize);
    } else {
        m_targetFormat = targetSwFormat;
        m_stream->codecpar->format = targetSwFormat;
    }
    auto cleanup = QScopeGuard([this] {
        if (m_accel)
            m_accel->destroyFramesContext();
    });
 
    if (m_accel && !m_accel->hwFramesContextAsBuffer()) {
        qCDebug(qLcVideoFrameEncoder)
                << "Failed to create frames context for targetSwFormat" << targetSwFormat;
        return false;
    }
 
    if (!initCodecContext())
        return false;
 
    if (!open())
        return false;
 
    cleanup.dismiss();
    updateConversions();
    return true;
}
 
VideoFrameEncoder::~VideoFrameEncoder() = default;
 
void VideoFrameEncoder::initStream()
{
    m_stream->codecpar->codec_id = m_codec.id();
 
    // Apples HEVC decoders don't like the hev1 tag ffmpeg uses by default, use hvc1 as the more
    // commonly accepted tag
    if (m_codec.id() == AV_CODEC_ID_HEVC)
        m_stream->codecpar->codec_tag = MKTAG('h', 'v', 'c', '1');
    else
        m_stream->codecpar->codec_tag = 0;
 
    // ### Fix hardcoded values
    m_stream->codecpar->format = m_targetFormat;
    m_stream->codecpar->width = m_targetSize.width();
    m_stream->codecpar->height = m_targetSize.height();
    m_stream->codecpar->sample_aspect_ratio = AVRational{ 1, 1 };
#if QT_CODEC_PARAMETERS_HAVE_FRAMERATE
    // Some codecs (e.g. Windows Media Foundation encoders) require a concrete,
    // non-zero frame rate
    m_stream->codecpar->framerate = effectiveCodecFrameRate();
#endif
 
    const auto frameRates = m_codec.frameRates();
    const bool isFixedRate = m_codecFrameRate.den > 0 && m_codecFrameRate.num > 0;
    m_stream->time_base = adjustFrameTimeBase(frameRates, effectiveCodecFrameRate(), isFixedRate);
}
 
bool VideoFrameEncoder::initCodecContext()
{
    namespace views = QtMultimediaPrivate::views;
 
    Q_ASSERT(m_stream->codecpar->codec_id);
 
    m_codecContext.reset(avcodec_alloc_context3(m_codec.get()));
    if (!m_codecContext) {
        qWarning() << "Could not allocate codec context";
        return false;
    }
 
    // copies format, size, color params, framerate
    const int status = avcodec_parameters_to_context(m_codecContext.get(), m_stream->codecpar);
    if (status < 0) {
        qCWarning(qLcVideoFrameEncoder)
                << "Cannot set codec parameters; result:" << AVError(status);
        return false;
    }
 
#if !QT_CODEC_PARAMETERS_HAVE_FRAMERATE
    m_codecContext->framerate = effectiveCodecFrameRate();
#endif
    m_codecContext->time_base = m_stream->time_base;
    qCDebug(qLcVideoFrameEncoder) << "codecContext time base" << m_codecContext->time_base.num
                                  << m_codecContext->time_base.den;
 
    if (m_needsGlobalHeader)
        m_codecContext->flags |= AV_CODEC_FLAG_GLOBAL_HEADER;
 
    if (m_accel) {
        const AVHWDeviceType deviceType = m_accel->deviceType();
        auto hwConfigs = m_codec.hwConfigs();
        auto matchingConfigs = hwConfigs | views::filter([&](const AVCodecHWConfig *cfg) {
            return cfg->device_type == deviceType;
        });
 
        bool supportsDeviceCtx = false;
        bool supportsFramesCtx = false;
        for (const AVCodecHWConfig *cfg : matchingConfigs) {
            if (cfg->methods & AV_CODEC_HW_CONFIG_METHOD_HW_DEVICE_CTX)
                supportsDeviceCtx = true;
            if (cfg->methods & AV_CODEC_HW_CONFIG_METHOD_HW_FRAMES_CTX)
                supportsFramesCtx = true;
        }
 
        if (supportsDeviceCtx) {
            auto deviceContext = m_accel->hwDeviceContextAsBuffer();
            Q_ASSERT(deviceContext);
            m_codecContext->hw_device_ctx = av_buffer_ref(deviceContext);
        }
 
        if (supportsFramesCtx)
            if (auto framesContext = m_accel->hwFramesContextAsBuffer())
                m_codecContext->hw_frames_ctx = av_buffer_ref(framesContext);
    }
 
    return true;
}
 
bool VideoFrameEncoder::open()
{
    Q_ASSERT(m_codecContext);
 
    AVDictionaryHolder opts;
    applyVideoEncoderOptions(m_settings, m_codec.name(), m_codecContext.get(), opts);
    applyExperimentalCodecOptions(m_codec, opts);
 
    qCDebug(qLcVideoFrameEncoder) << "Opening encoder" << m_codec.name() << "with" << opts;
 
    int res = avcodec_open2(m_codecContext.get(), m_codec.get(), opts);
    if (res < 0) {
        qCWarning(qLcVideoFrameEncoder)
                << "Couldn't open video encoder" << m_codec.name() << "; result:" << AVError(res);
        return false;
    }
    qCDebug(qLcVideoFrameEncoder) << "video codec opened" << res << "time base"
                                  << m_codecContext->time_base;
 
    res = avcodec_parameters_from_context(m_stream->codecpar, m_codecContext.get());
    if (res < 0) {
        qCWarning(qLcVideoFrameEncoder) << "Cannot get parameters from video codec context"
                                        << m_codec.name() << "; result:" << AVError(res);
        return false;
    }
 
    return true;
}
 
qreal VideoFrameEncoder::codecFrameRate() const
{
    return m_codecFrameRate.den ? qreal(m_codecFrameRate.num) / m_codecFrameRate.den : 0.;
}
 
qint64 VideoFrameEncoder::getPts(qint64 us) const
{
    qint64 div = 1'000'000 * m_stream->time_base.num;
    return div != 0 ? (us * m_stream->time_base.den + div / 2) / div : 0;
}
 
const AVRational &VideoFrameEncoder::getTimeBase() const
{
    return m_stream->time_base;
}
 
namespace {
struct FrameConverter
{
    FrameConverter(AVFrameUPtr inputFrame) : m_inputFrame{ std::move(inputFrame) } { }
 
    int downloadFromHw()
    {
        AVFrameUPtr cpuFrame = makeAVFrame();
 
        int err = av_hwframe_transfer_data(cpuFrame.get(), currentFrame(), 0);
        if (err < 0) {
            qCDebug(qLcVideoFrameEncoder)
                    << "Error transferring frame data to surface." << AVError(err);
            return err;
        }
 
        setFrame(std::move(cpuFrame));
        return 0;
    }
 
    void convert(SwsContext *scaleContext, AVPixelFormat format, const QSize &size)
    {
        AVFrameUPtr scaledFrame = makeAVFrame();
 
        scaledFrame->format = format;
        scaledFrame->width = size.width();
        scaledFrame->height = size.height();
 
        const int status = av_frame_get_buffer(scaledFrame.get(), 0);
        if (status < 0) {
            qCWarning(qLcVideoFrameEncoder)
                    << "Failed to allocate scaled frame buffer:" << AVError(status);
            return;
        }
 
        const AVFrame *srcFrame = currentFrame();
 
        const auto scaledHeight =
                sws_scale(scaleContext, srcFrame->data, srcFrame->linesize, 0, srcFrame->height,
                          scaledFrame->data, scaledFrame->linesize);
 
        if (scaledHeight != scaledFrame->height)
            qCWarning(qLcVideoFrameEncoder)
                    << "Scaled height" << scaledHeight << "!=" << scaledFrame->height;
 
        setFrame(std::move(scaledFrame));
    }
 
    int uploadToHw(HWAccel *accel)
    {
        auto *hwFramesContext = accel->hwFramesContextAsBuffer();
        Q_ASSERT(hwFramesContext);
        AVFrameUPtr hwFrame = makeAVFrame();
        if (!hwFrame)
            return AVERROR(ENOMEM);
 
        int err = av_hwframe_get_buffer(hwFramesContext, hwFrame.get(), 0);
        if (err < 0) {
            qCDebug(qLcVideoFrameEncoder) << "Error getting HW buffer" << AVError(err);
            return err;
        } else {
            qCDebug(qLcVideoFrameEncoder) << "got HW buffer";
        }
        if (!hwFrame->hw_frames_ctx) {
            qCDebug(qLcVideoFrameEncoder) << "no hw frames context";
            return AVERROR(ENOMEM);
        }
        err = av_hwframe_transfer_data(hwFrame.get(), currentFrame(), 0);
        if (err < 0) {
            qCDebug(qLcVideoFrameEncoder)
                    << "Error transferring frame data to surface." << AVError(err);
            return err;
        }
 
        setFrame(std::move(hwFrame));
 
        return 0;
    }
 
    q23::expected<AVFrameUPtr, int> takeResultFrame()
    {
        // Ensure that object is reset to empty state
        AVFrameUPtr converted = std::move(m_convertedFrame);
        AVFrameUPtr input = std::move(m_inputFrame);
 
        if (!converted)
            return input;
 
        // Copy metadata except size and format from input frame
        const int status = av_frame_copy_props(converted.get(), input.get());
        if (status != 0)
            return q23::unexpected{ status };
 
        return converted;
    }
 
private:
    void setFrame(AVFrameUPtr frame) { m_convertedFrame = std::move(frame); }
 
    AVFrame *currentFrame() const
    {
        if (m_convertedFrame)
            return m_convertedFrame.get();
        return m_inputFrame.get();
    }
 
    AVFrameUPtr m_inputFrame;
    AVFrameUPtr m_convertedFrame;
};
} // namespace
 
int VideoFrameEncoder::sendFrame(AVFrameUPtr inputFrame)
{
    if (!m_codecContext) {
        qWarning() << "codec context is not initialized!";
        return AVERROR(EINVAL);
    }
 
    if (!inputFrame)
        return avcodec_send_frame(m_codecContext.get(), nullptr); // Flush
 
    if (!updateSourceFormatAndSize(inputFrame.get()))
        return AVERROR(EINVAL);
 
    // some codecs require quality to be set on each frame and ignore global_quality
    inputFrame->quality = m_codecContext->global_quality;
 
    FrameConverter converter{ std::move(inputFrame) };
 
    if (m_downloadFromHW) {
        const int status = converter.downloadFromHw();
        if (status != 0)
            return status;
    }
 
    if (m_scaleContext)
        converter.convert(m_scaleContext.get(), m_targetSWFormat, m_targetSize);
 
    if (m_uploadToHW) {
        const int status = converter.uploadToHw(m_accel.get());
        if (status != 0)
            return status;
    }
 
    const q23::expected<AVFrameUPtr, int> resultFrame = converter.takeResultFrame();
    if (!resultFrame)
        return resultFrame.error();
 
    AVRational timeBase{};
    int64_t pts{};
    getAVFrameTime(*resultFrame.value(), pts, timeBase);
    qCDebug(qLcVideoFrameEncoder) << "sending frame" << pts << "*" << timeBase;
 
    return avcodec_send_frame(m_codecContext.get(), resultFrame.value().get());
}
 
qint64 VideoFrameEncoder::estimateDuration(const AVPacket &packet, bool isFirstPacket)
{
    qint64 duration = 0; // In stream units, multiply by time_base to get seconds
 
    if (isFirstPacket) {
        // First packet - Estimate duration from frame rate. Duration must
        // be set for single-frame videos, otherwise they won't open in
        // media player. The codec frame rate is 0 for variable-rate sources,
        // so fall back to a default rate to avoid dividing by zero.
        AVRational frameRate = m_codecContext->framerate;
        if (frameRate.num <= 0)
            frameRate = AVRational{ DefaultVideoFrameRate, 1 };
 
        const AVRational frameDuration = av_inv_q(frameRate);
        duration = av_rescale_q(1, frameDuration, m_stream->time_base);
    } else {
        // Duration is calculated from actual packet times. TODO: Handle discontinuities
        duration = packet.pts - m_lastPacketTime;
    }
 
    return duration;
}
 
AVPacketUPtr VideoFrameEncoder::retrievePacket()
{
    if (!m_codecContext)
        return nullptr;
 
    auto getPacket = [&]() {
        AVPacketUPtr packet(av_packet_alloc());
        const int ret = avcodec_receive_packet(m_codecContext.get(), packet.get());
        if (ret < 0) {
            if (ret != AVERROR(EOF) && ret != AVERROR(EAGAIN) && ret != AVERROR_EOF)
                qCDebug(qLcVideoFrameEncoder) << "Error receiving packet" << ret << AVError(ret);
            return AVPacketUPtr{};
        }
        auto ts = timeStampMs(packet->pts, m_stream->time_base);
 
        qCDebug(qLcVideoFrameEncoder)
                << "got a packet" << packet->pts << packet->dts << (ts ? *ts : 0);
 
        packet->stream_index = m_stream->id;
 
        if (packet->duration == 0) {
            const bool firstFrame = m_lastPacketTime == AV_NOPTS_VALUE;
            packet->duration = estimateDuration(*packet, firstFrame);
        }
 
        m_lastPacketTime = packet->pts;
 
        return packet;
    };
 
    auto fixPacketDts = [&](AVPacket &packet) {
        // Workaround for some ffmpeg codecs bugs (e.g. nvenc)
        // Ideally, packet->pts < packet->dts is not expected
 
        if (packet.dts == AV_NOPTS_VALUE)
            return true;
 
        packet.dts -= m_packetDtsOffset;
 
        if (packet.pts != AV_NOPTS_VALUE && packet.pts < packet.dts) {
            m_packetDtsOffset += packet.dts - packet.pts;
            packet.dts = packet.pts;
 
            if (m_prevPacketDts != AV_NOPTS_VALUE && packet.dts < m_prevPacketDts) {
                qCWarning(qLcVideoFrameEncoder)
                        << "Skip packet; failed to fix dts:" << packet.dts << m_prevPacketDts;
                return false;
            }
        }
 
        m_prevPacketDts = packet.dts;
 
        return true;
    };
 
    while (auto packet = getPacket()) {
        if (fixPacketDts(*packet))
            return packet;
    }
 
    return nullptr;
}
 
bool VideoFrameEncoder::updateSourceFormatAndSize(const AVFrame *frame)
{
    Q_ASSERT(frame);
 
    const QSize frameSize(frame->width, frame->height);
    const AVPixelFormat frameFormat = static_cast<AVPixelFormat>(frame->format);
 
    if (frameSize == m_sourceSize && frameFormat == m_sourceFormat)
        return true;
 
    auto applySourceFormatAndSize = [&](AVPixelFormat swFormat) {
        m_sourceSize = frameSize;
        m_sourceFormat = frameFormat;
        m_sourceSWFormat = swFormat;
        updateConversions();
        return true;
    };
 
    if (frameFormat == m_sourceFormat)
        return applySourceFormatAndSize(m_sourceSWFormat);
 
    if (frameFormat == AV_PIX_FMT_NONE) {
        qWarning() << "Got a frame with invalid pixel format";
        return false;
    }
 
    if (isSwPixelFormat(frameFormat))
        return applySourceFormatAndSize(frameFormat);
 
    auto framesCtx = reinterpret_cast<const AVHWFramesContext *>(frame->hw_frames_ctx->data);
    if (!framesCtx || framesCtx->sw_format == AV_PIX_FMT_NONE) {
        qWarning() << "Cannot update conversions as hw frame has invalid framesCtx" << framesCtx;
        return false;
    }
 
    return applySourceFormatAndSize(framesCtx->sw_format);
}
 
void VideoFrameEncoder::updateConversions()
{
    const bool needToScale = m_sourceSize != m_targetSize;
    const bool zeroCopy = m_sourceFormat == m_targetFormat && !needToScale;
 
    m_scaleContext.reset();
 
    if (zeroCopy) {
        m_downloadFromHW = false;
        m_uploadToHW = false;
 
        qCDebug(qLcVideoFrameEncoder) << "zero copy encoding, format" << m_targetFormat;
        // no need to initialize any converters
        return;
    }
 
    m_downloadFromHW = m_sourceFormat != m_sourceSWFormat;
    m_uploadToHW = m_targetFormat != m_targetSWFormat;
 
    if (m_sourceSWFormat != m_targetSWFormat || needToScale) {
        qCDebug(qLcVideoFrameEncoder)
                << "video source and encoder use different formats:" << m_sourceSWFormat
                << m_targetSWFormat << "or sizes:" << m_sourceSize << m_targetSize;
 
        const SwsFlags conversionType = getScaleConversionType(m_sourceSize, m_targetSize);
 
        m_scaleContext = createSwsContext(m_sourceSize, m_sourceSWFormat, m_targetSize,
                                          m_targetSWFormat, conversionType);
    }
 
    qCDebug(qLcVideoFrameEncoder) << "VideoFrameEncoder conversions initialized:"
                                  << "sourceFormat:" << m_sourceFormat
                                  << (isHwPixelFormat(m_sourceFormat) ? "(hw)" : "(sw)")
                                  << "targetFormat:" << m_targetFormat
                                  << (isHwPixelFormat(m_targetFormat) ? "(hw)" : "(sw)")
                                  << "sourceSWFormat:" << m_sourceSWFormat
                                  << "targetSWFormat:" << m_targetSWFormat
                                  << "scaleContext:" << m_scaleContext.get();
}
 
} // namespace QFFmpeg
 
QT_END_NAMESPACE