[flac-dev] Disable all checksum verification in flac/metaflac

Manuel Bertsch malu.bertsch at gmail.com
Thu Jun 29 20:28:39 UTC 2023

Hello all,


I’m trying to use flac and metaflac as tooling to analyze the generated FLAC
files of a new encoder implementation. However, while my own third-party
decoder can handle the output just fine, flac, metaflac, and other tools
discard the output since the frame checksum (footer CRC-16) is invalid. This
is expected, since I have no checksum generation implemented apart from the
frame header checksum (all other checksums are written as 0), but it
prevents me from making development process without being able to check my
outputs against the reference implementation. I looked around and I couldn’t
find a way to turn off either tool’s checksum verification. So I’d like to
know how one could turn off checksum verification in the tools, and if
that’s not currently possible, I’d like to see that as a feature in a future
version of flac. (In that case I would also try to disable the checks in
code permanently, though my solution is most likely not going to be
upstreamable in any capacity.)


FYI, the third-party decoder is highly compliant according to the spec test
suite, producing identical audio playback on almost all of the files, but it
also doesn’t verify or error on any checksums. ffplay and ffmpeg both accept
the file and can play and transcode it correctly, although they ignore the
sample count in the streaminfo header and will read all frames they can
find. The latter leads me to believe that checksums are the actual issue,
even though flac reports the generic “Bad Header” and “Lost Sync”.


Greetings and thanks in advance,


Kleines Filmröllchen

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