LMMS / LMMS/lmms

Sound is distorted/white noise on big endian platforms

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bug
Dominant language
C++
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Description

I maintain Adélie Linux, a Linux distro focused on non-x86 systems.

I've just built LMMS 1.2.0-rc7 on my Talos II, a POWER9 based workstation (new in 2018, and more models launching in 2019). It works pretty well (after applying the patch from #4009); however, audio output is just white noise. It feels like an endianness issue to me. I've tried the PulseAudio and ALSA backends.

Other software, such as Audacious, Firefox, and Pidgin, can use Pulse just fine; raw ALSA can work but it needs to be set in s16le mode (as the Creative DAC in my Talos doesn't work with s16be).

Trying to fiddle with m_convertEndian (forcing to true, or false, or leaving it detecting) didn't help, unfortunately, though I only tried it with Pulse.

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First steps

  1. Read the whole issue, then the project's contributing guide.
  2. Comment on the issue to say you are picking it up — it saves two people doing the same work.
  3. Fork the repository and make your change on a branch.
  4. Open a pull request that references the issue number.

Research direction

Start by reproducing the white-noise output on the Talos II or another big-endian system, comparing the PulseAudio and ALSA backends. Inspect the audio sample-format and m_convertEndian handling, including the reported s16le versus s16be behavior. Done means audio output is correct on big-endian hardware without breaking the existing backends.

Written by the indexing model from the issue text.

Assessment

Tech stack
cpp, linux
Domain
audio-video-rtc
Issue type
Bug
Difficulty
4/5
Estimated time
3-5 days
Activity status
Stale
Clarity
Mostly clear
Newbie friendliness
35/100

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