Method MaybeReorderFrames

src/core/track.cpp:213–249

}

void FFMS_Track::MaybeReorderFrames() {
    frame_vec &Frames = Data->Frames;
    // First check if we need to do anything
    bool has_b_frames = false;
    for (size_t i = 1; i < size(); ++i) {
        // If the timestamps are already out of order, then they actually are
        // presentation timestamps and we don't need to do anything
        if (Frames[i].PTS < Frames[i - 1].PTS)
            return;

        if (Frames[i].FrameType == AV_PICTURE_TYPE_B) {
            has_b_frames = true;

            // Reordering files with multiple b-frames is currently not
            // supported
            if (Frames[i - 1].FrameType == AV_PICTURE_TYPE_B)
                return;
        }
    }

    // Don't need to do anything if there are no b-frames as presentation order
    // equals decoding order
    if (!has_b_frames)
        return;

    // We have b-frames, but the timestamps are monotonically increasing. This
    // means that the timestamps we have are decoding timestamps, and we want
    // presentation time stamps. Convert DTS to PTS by swapping the timestamp
    // of each b-frame with the frame before it. This only works for the
    // specific case of b-frames which reference the frame immediately after
    // them temporally, but that happens to cover the only files I've seen
    // with b-frames and no presentation timestamps.
    for (size_t i = 1; i < size(); ++i) {
        if (Frames[i].FrameType == AV_PICTURE_TYPE_B)
            std::swap(Frames[i].PTS, Frames[i - 1].PTS);
    }
}

void FFMS_Track::RevertToDTS() {
    frame_vec &Frames = Data->Frames;