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

[Martijn van Beurden]

Hi,

Is it possible for you to compile flac/metaflac yourself? Then you'll only
need to remove a few lines, namely these 4:
https://github.com/xiph/flac/blob/28e4f0528c76b296c561e922ba67d43751990599/src/libFLAC/stream_decoder.c#L2118-L2121
and these 7:
https://github.com/xiph/flac/blob/28e4f0528c76b296c561e922ba67d43751990599/src/libFLAC/stream_decoder.c#L2141-L2147
As you can see these lines are also disabled on fuzzing.

I think providing an API function and flac+metaflac command line option is
going to be confusing and they will probably be misused. A compile time
option might be possible though, libogg provides that too.

Kind regards,

Martijn van Beurden

Op do 29 jun. 2023 22:28 schreef Manuel Bertsch <malu.bertsch at gmail.com>:

> 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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> flac-dev at xiph.org
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>
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