Method GetSeekablePacketNumber

src/core/audiosource.cpp:459–493

}

size_t FFMS_AudioSource::GetSeekablePacketNumber(FFMS_Track const& Frames, size_t PacketNumber) {
    // Packets don't always have unique PTSes, so we may not be able to
    // uniquely identify the packet we want. This function attempts to find
    // a PTS we can seek to which will let us figure out which packet we're
    // on before we get to the packet we actually wanted

    // MatroskaAudioSource doesn't need this, as it seeks by byte offset
    // rather than PTS. LAVF theoretically can seek by byte offset, but we
    // don't use it as not all demuxers support it and it's broken in some of
    // those that claim to support it

    // However much we might wish to, we can't seek to before packet zero
    if (PacketNumber == 0) return PacketNumber;

    // Desired packet's PTS is unique, so don't do anything
    if (Frames[PacketNumber].PTS != Frames[PacketNumber - 1].PTS &&
        (PacketNumber + 1 == Frames.size() || Frames[PacketNumber].PTS != Frames[PacketNumber + 1].PTS))
        return PacketNumber;

    // When decoding, we only reliably know what packet we're at when the
    // newly parsed packet has a different PTS from the previous one. As such,
    // we walk backwards until we hit a different PTS and then seek to there,
    // so that we can then decode until we hit the PTS group we actually wanted
    // (and thereby know that we're at the first packet in the group rather
    // than whatever the splitter happened to choose)

    // This doesn't work if our desired packet has the same PTS as the first
    // packet, but this scenario should never come up anyway; we permanently
    // cache the decoded results from those packets, so there's no need to ever
    // seek to them
    int64_t PTS = Frames[PacketNumber].PTS;
    while (PacketNumber > 0 && PTS == Frames[PacketNumber].PTS)
        --PacketNumber;
    return PacketNumber;
}

void FFMS_AudioSource::OpenFile() {
    avcodec_free_context(&CodecContext);