Assuming that a flac stream starts with bytes
['f', 'L', 'a', 'C', 0, 0, 0, 0x22] is not always correct as it could
also start with ['f', 'L', 'a', 'C', 0x80, 0, 0, 0x22]
(see https://xiph.org/flac/format.html#metadata_block_streaminfo).
PiperOrigin-RevId: 279080562
