AP4_Track *test_videoTrack = nullptr;
AP4_ByteStream *input = nullptr;
AP4_Result result = AP4_FileByteStream::Create(filename, AP4_FileByteStream::STREAM_MODE_READ, input);

AP4_File m_file (*input, true);

//
// Read movie tracks, and metadata, find the video track
size_t index = 0;
uint32_t m_width = 0, m_height = 0;
auto item = m_file.GetMovie()->GetTracks().FirstItem();
auto track = item->GetData();
if (track->GetType() == AP4_Track::TYPE_VIDEO)
{
    m_width = (uint32_t)((double)test_videoTrack->GetWidth() / double(1 << 16));
    m_height = (uint32_t)((double)test_videoTrack->GetHeight() / double(1 << 16));

    std::string codec("unknown");
    auto sd = track->GetSampleDescription(0);
    AP4_String c;
    if (AP4_SUCCEEDED(sd->GetCodecString(c)))
    {
        codec = c.GetChars();
    }

    // Find and instantiate the decoder
    AP4_Sample sample;
    AP4_DataBuffer sampleData;
    test_videoTrack->ReadSample(0, sample, sampleData);
}