Function ReadStream

Source/Engine/Video/MF/VideoBackendMF.cpp:195–386

    }

    bool ReadStream(VideoBackendPlayer& player, VideoPlayerMF& playerMF, DWORD streamIndex, TimeSpan dt)
    {
        PROFILE_CPU_NAMED("ReadStream");
        ZoneText(player.DebugUrl, player.DebugUrlLen);
        const bool isVideo = streamIndex == MF_SOURCE_READER_FIRST_VIDEO_STREAM;
        const bool isAudio = streamIndex == MF_SOURCE_READER_FIRST_AUDIO_STREAM;
        int32 goodSamples = 1;
        TimeSpan validTimeRangeStart(0), validTimeRangeEnd(0);
        if (isAudio)
        {
            constexpr int32 AudioFramesQueue = 10; // How many frames to read into the audio buffers queue in advance (to improve audio playback smoothness)
            if (player.AudioBufferDuration.Ticks == 0)
            {
                // Read more samples for audio to enqueue multiple audio buffers for smoother playback
                goodSamples = AudioFramesQueue;
            }
            else
            {
                // Skip reading if the last sample was already over this range (we've got enough in a queue)
                validTimeRangeStart = player.AudioBufferTime - player.AudioBufferDuration * AudioFramesQueue;
                validTimeRangeEnd = validTimeRangeStart + player.AudioBufferDuration;
                if (Math::IsInRange(playerMF.Time, validTimeRangeStart, validTimeRangeEnd))
                {
                    return false;
                }

                // Allow to read future samples within queue range
                validTimeRangeStart = player.AudioBufferTime - player.AudioBufferDuration;
                validTimeRangeEnd = player.AudioBufferTime + player.AudioBufferDuration * AudioFramesQueue;

                // Read more samples to keep queue at capacity
                TimeSpan targetQueueEnd = playerMF.Time + player.AudioBufferDuration * AudioFramesQueue;
                TimeSpan activeBufferEnd = player.AudioBufferTime + player.AudioBufferDuration;
                TimeSpan missingQueueDuration = targetQueueEnd - activeBufferEnd;
                goodSamples = (int32)Math::DivideAndRoundUp(missingQueueDuration.Ticks, player.AudioBufferDuration.Ticks);
                if (goodSamples < 1)
                    goodSamples = 1;
            }
        }
        else if (isVideo)
        {
            // Check if the current frame is valid (eg. when playing 24fps video at 60fps)
            if (player.VideoFrameDuration.Ticks > 0 &&
                Math::IsInRange(playerMF.Time, player.VideoFrameTime, player.VideoFrameTime + player.VideoFrameDuration))
            {
                return false;
            }
        }

        // Read samples until frame is matching the current time
        int32 samplesLeft = 500;
        int32 goodSamplesLeft = goodSamples;
        HRESULT hr;
        for (; samplesLeft > 0 && goodSamplesLeft > 0; samplesLeft--)
        {
            // Read sample
            DWORD flags = 0;
            LONGLONG samplePos = 0, sampleDuration = 0;