[pkg-mad-maintainers] Bug#881283: libmad0: produces different results on s390x/arm64/...

[IOhannes m zmoelnig]

Package: libmad0
Version: 0.15.1b-8.1
Severity: important

Dear Maintainer,

TL;DR: it seems that libmad is not really usable on s390x.

i'm currently trying to find out why sonic-visualiser_3.0.3-1 fails to build
successfully on the s390x and arm64 architectures.
The problem is a failing test when decoding mp3 files.
The test runs fine on most release architectures, but fails on
- arm64
- s390x
- alpha
- hppa
- m68k
- sh4

Now while trying to hunt this down, i think i found an issue with libmad.
Using the following test-program:

    #!/usr/bin/env python

    import mad
    mf = mad.MadFile("sine.mp3")
    data = mf.read()

    offset = 2048
    print([_ for _ in data[offset:(offset+1024)]])


and the attached minimal MP3-file "sine.mp3" i get different results for s390x
(zelenka.debian.org) and amd64 (my laptop):

s390x = [  0,   1,   0,   1, 255, 254, 255, 254, 255, 252, 255, 252, 0, 5, ...
amd64 = [252, 255, 252, 255, 254, 255, 254, 255,   0,   0,   0,   0, 1, 0, ...

I've also ran the file through the 'minimad' example that comes with libmad
(sources), and the output differs on the two architectures (i've attached the
results as 's390x.bin' resp.  'amd64.bin').
i haven't done any checks on architectures that are supposed to be "ok"
(according to my test-suite).

Would it be possible to fix this?
If not, should the failing architectures be marked as "not-for-us"?

mgfasdr
IOhannes


-- System Information:
Debian Release: buster/sid
  APT prefers stable-updates
  APT policy: (500, 'stable-updates'), (500, 'unstable'), (500, 'stable')
Architecture: amd64 (x86_64)

Kernel: Linux 4.13.0-1-amd64 (SMP w/4 CPU cores)
Locale: LANG=en_US.utf8, LC_CTYPE=en_US.utf8 (charmap=UTF-8), LANGUAGE=en_US.utf8 (charmap=UTF-8)
Shell: /bin/sh linked to /bin/dash
Init: systemd (via /run/systemd/system)

Versions of packages libmad0 depends on:
ii  libc6  2.24-17

libmad0 recommends no packages.

libmad0 suggests no packages.

-- no debconf information
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