[LigH]

It may surprise you ... but L-SMASH Works contains a README file.

According to this one, there seems to be no cache file for the functions using the L-SMASH demultiplexer:

            LSMASHVideoSource(string source, int track = 0, int threads = 0, int seek_mode = 0, int seek_threshold = 10,
                              bool dr = false, int fpsnum = 0, int fpsden = 1, bool stacked = false, string format = "")

In contrast to the functions using libavformat as demultiplexer:

            LWLibavVideoSource(string source, int stream_index = -1, int threads = 0, bool cache = true,
                               int seek_mode = 0, int seek_threshold = 10, bool dr = false,
                               int fpsnum = 0, int fpsden = 1,
                               bool repeat = false, int dominance = 0, bool stacked = false, string format = "")

So it seems quite probable that LSMASHVideoSource() relies on media file internal index chunks. It will support only a few specific media formats, though: MP4, MOV, 3GPP