Method CacheBeginning

src/core/audiosource.cpp:164–204

}

void FFMS_AudioSource::CacheBeginning() {
    // Nothing to do if the cache is already populated
    if (!Cache.empty()) return;

    // The first packet after a seek is often decoded incorrectly, which
    // makes it impossible to ever correctly seek back to the beginning, so
    // store the first block now

    // In addition, anything with the same PTS as the first packet can't be
    // distinguished from the first packet and so can't be seeked to, so
    // store those as well

    // Some of LAVF's splitters don't like to seek to the beginning of the
    // file (ts and?), so cache a few blocks even if PTSes are unique
    // Packet 7 is the last packet I've had be unseekable to, so cache up to
    // 10 for a bit of an extra buffer
    auto end = Cache.end();
    while (PacketNumber < Frames.size() &&
        ((Frames[0].PTS != AV_NOPTS_VALUE && Frames[PacketNumber].PTS == Frames[0].PTS) ||
            Cache.size() < 10)) {

        // Vorbis in particular seems to like having 60+ packets at the start
        // of the file with a PTS of 0, so we might need to expand the search
        // range to account for that.
        // Expanding slightly before it's strictly needed to ensure there's a
        // bit of space for an actual cache
        if (Cache.size() >= MaxCacheBlocks - 5) {
            if (MaxCacheBlocks >= EXCESSIVE_CACHE_SIZE)
                throw FFMS_Exception(FFMS_ERROR_DECODING, FFMS_ERROR_ALLOCATION_FAILED,
                    "Exceeded the search range for an initial valid audio PTS");
            MaxCacheBlocks *= 2;
        }

        DecodeNextBlock(&end);
    }
    // Store the iterator to the last element of the cache which is used for
    // correctness rather than speed, so that when looking for one to delete
    // we know how much to skip
    CacheNoDelete = Cache.end();
    --CacheNoDelete;
}

static int PopCount(int64_t v) {
    int c = 0;