https://ffmpeg.org/pipermail/ffmpeg-user/2015-April/025906.html
https://trac.ffmpeg.org/ticket/4421
Some ffmpeg-encoded FLAC files can be successfully decoded by ffmpeg,
but not FLAC. So it's either a bug somewhere (presumably in ffmpeg, but
maybe in FLAC), or ffmpeg treats something differently than FLAC.
libFLAC has routines like FLAC__lpc_compute_residual_from_qlp_coefficients
and FLAC__lpc_restore_signal (and their ..._wide counterparts).
libFLAC doens't allow the "sum" variable in them to overflow,
right? It seems
that ffmpeg routines allow this, and that's the reason of these problems.
