SDL: SDL 3 Loopwave : Audio no output and code freeze on USB Headphone via PulseAudio driver

Reference in https://github.com/exult/exult/issues/379

Problem description

Test with loopwave, Linux Fedora 39, USB Headphones over PipeWire, the SDL default driver is PulseAudio => no audio output, and code freeze :

build/test/loopwave --log all
INFO: Available audio drivers:
INFO: 0: pulseaudio
INFO: 1: pipewire
INFO: 2: alsa
INFO: 3: jack
INFO: 4: dsp
INFO: 5: disk
INFO: 6: dummy
INFO: Using audio driver: pulseaudio
<- No audio output, code freeze, does not stop with Ctl-C, must use kill -9 from another session

The SDL drivers PipeWire or ALSA work OK :

SDL_AUDIO_DRIVER=pipewire build/test/loopwave --log all

The SDL driver Jack fails with :

DEBUG: Parameter 'dst_spec->channels' is invalid
ERROR: Couldn't create audio stream: Parameter 'dst_spec->channels' is invalid

The SDL driver DSP fails with :

DEBUG: dsp: No such audio device
ERROR: Couldn't initialize SDL: dsp: No such audio device

The PulseAudio ( pacat -p ) and Pipewire ( pw-cat -p ) play command lines work OK.

When the audio is routed to the PCIe Audio card to Loudspeakers - by switching off the Headphone -, then loopwave with PulseAudio works.

With loopwave via PulseAudio to the USB Headphone under GDB, at code freeze, break with Ctl-C, the GDB query threads returns :

(gdb) info threads
  Id   Target Id                                         Frame 
* 1    Thread 0x7ffff7f32480 (LWP 21213) "loopwave"      0x00007ffff7af71a3 in clock_nanosleep@GLIBC_2.2.5 () from /lib64/libc.so.6
  2    Thread 0x7ffff72ec6c0 (LWP 21216) "PulseMainloop" 0x00007ffff7b25bcd in poll () from /lib64/libc.so.6
  3    Thread 0x7ffff7fb96c0 (LWP 21217) "PulseHotplug"  0x00007ffff7aa9169 in __futex_abstimed_wait_common () from /lib64/libc.so.6
  4    Thread 0x7ffff2a756c0 (LWP 21218) "SDLAudioP27"   0x00007ffff7aa9169 in __futex_abstimed_wait_common () from /lib64/libc.so.6
(gdb) t 1
[Switching to thread 1 (Thread 0x7ffff7f32480 (LWP 21213))]
#0  0x00007ffff7af71a3 in clock_nanosleep@GLIBC_2.2.5 () from /lib64/libc.so.6
(gdb) bt
#0  0x00007ffff7af71a3 in clock_nanosleep@GLIBC_2.2.5 () from /lib64/libc.so.6
#1  0x00007ffff7b09a37 in nanosleep () from /lib64/libc.so.6
#2  0x00007ffff7e61fa2 in SDL_DelayNS_REAL () from <edited>/SDL.git/build/libSDL3.so.0
#3  0x00007ffff7e628d4 in SDL_EnterAppMainCallbacks_REAL () from <edited>/SDL.git/build/libSDL3.so.0
#4  0x00007ffff7c59228 in SDL_EnterAppMainCallbacks () from <edited>/SDL.git/build/libSDL3.so.0
#5  0x0000000000404b59 in SDL_main ()
#6  0x00007ffff7c46e14 in SDL_RunApp_REAL () from <edited>/SDL.git/build/libSDL3.so.0
#7  0x00007ffff7c4c756 in SDL_RunApp_DEFAULT () from <edited>/SDL.git/build/libSDL3.so.0
#8  0x00007ffff7c55cb9 in SDL_RunApp () from <edited>/SDL.git/build/libSDL3.so.0
#9  0x0000000000404b82 in main ()
(gdb) t 2
[Switching to thread 2 (Thread 0x7ffff72ec6c0 (LWP 21216))]
#0  0x00007ffff7b25bcd in poll () from /lib64/libc.so.6
(gdb) bt
#0  0x00007ffff7b25bcd in poll () from /lib64/libc.so.6
#1  0x00007ffff76c7536 in poll_func () from /lib64/libpulse.so.0
#2  0x00007ffff76b0694 in pa_mainloop_poll () from /lib64/libpulse.so.0
#3  0x00007ffff76bb163 in pa_mainloop_iterate () from /lib64/libpulse.so.0
#4  0x00007ffff76bb228 in pa_mainloop_run () from /lib64/libpulse.so.0
#5  0x00007ffff76cb741 in thread () from /lib64/libpulse.so.0
#6  0x00007ffff766dccb in internal_thread_func () from /usr/lib64/pulseaudio/libpulsecommon-16.1.so
#7  0x00007ffff7aac897 in start_thread () from /lib64/libc.so.6
#8  0x00007ffff7b336fc in clone3 () from /lib64/libc.so.6
(gdb) t 3
[Switching to thread 3 (Thread 0x7ffff7fb96c0 (LWP 21217))]
#0  0x00007ffff7aa9169 in __futex_abstimed_wait_common () from /lib64/libc.so.6
(gdb) bt
#0  0x00007ffff7aa9169 in __futex_abstimed_wait_common () from /lib64/libc.so.6
#1  0x00007ffff7aabb09 in pthread_cond_wait@@GLIBC_2.3.2 () from /lib64/libc.so.6
#2  0x00007ffff76c85a4 in pa_threaded_mainloop_wait () from /lib64/libpulse.so.0
#3  0x00007ffff7df06b6 in HotplugThread () from <edited>/SDL.git/build/libSDL3.so.0
#4  0x00007ffff7ce2124 in SDL_RunThread () from <edited>/SDL.git/build/libSDL3.so.0
#5  0x00007ffff7e5e7a4 in RunThread () from <edited>/SDL.git/build/libSDL3.so.0
#6  0x00007ffff7aac897 in start_thread () from /lib64/libc.so.6
#7  0x00007ffff7b336fc in clone3 () from /lib64/libc.so.6
(gdb) t 4
[Switching to thread 4 (Thread 0x7ffff2a756c0 (LWP 21218))]
#0  0x00007ffff7aa9169 in __futex_abstimed_wait_common () from /lib64/libc.so.6
(gdb) bt
#0  0x00007ffff7aa9169 in __futex_abstimed_wait_common () from /lib64/libc.so.6
#1  0x00007ffff7aabb09 in pthread_cond_wait@@GLIBC_2.3.2 () from /lib64/libc.so.6
#2  0x00007ffff76c85a4 in pa_threaded_mainloop_wait () from /lib64/libpulse.so.0
#3  0x00007ffff7def3cd in PULSEAUDIO_WaitDevice () from <edited>/SDL.git/build/libSDL3.so.0
#4  0x00007ffff7c33a19 in OutputAudioThread () from <edited>/SDL.git/build/libSDL3.so.0
#5  0x00007ffff7ce2124 in SDL_RunThread () from <edited>/SDL.git/build/libSDL3.so.0
#6  0x00007ffff7e5e7a4 in RunThread () from <edited>/SDL.git/build/libSDL3.so.0
#7  0x00007ffff7aac897 in start_thread () from /lib64/libc.so.6
#8  0x00007ffff7b336fc in clone3 () from /lib64/libc.so.6
(gdb) q

Complement information

• PipeWire is installed as pipewire-(various-)1.0.0-2.fc39,

• PipeWire provides a PulseAudio API in installed pipewire-pulseaudio-1.0.0-2.fc39,

• The PulseAudio core pulseaudio-16.1-5.fc39 is not installed and cannot be installed because the installed pipewire-pulseaudio is in conflict,

• The PulseAudio library pulseaudio-libs-16.1-5.fc39 is installed.

• SDL 3 is at Git main of 2024-01-06, commit e100992c1, no mod.