SDL2 (version >=2.0) prefers float32 audio format over integer audio format. QEMU sdlaudio.c does not handle any kind of AUDIO_F32 formats, but SDL_OpenAudio(req, obt) will return float32 audio format in obt and QEMU prints error about unknown format 33056 (0x8120).

The following simple patch fix the error by forcing SDL2 internal audio format conversion.

diff -ru ../orig/qemu-4.2.0/audio/sdlaudio.c ../qemu-4.2.0/audio/sdlaudio.c

--- ../orig/qemu-4.2.0/audio/sdlaudio.c 2019-12-12 10:20:47.000000000 -0800

+++ ../qemu-4.2.0/audio/sdlaudio.c      2020-01-15 15:56:25.059841600 -0800

@@ -147,10 +147,11 @@

     }

#endif

-    status = SDL_OpenAudio (req, obt);

+    status = SDL_OpenAudio (req, NULL);

     if (status) {

         sdl_logerr ("SDL_OpenAudio failed\n");

     }

+    memcpy(obt, req, sizeof(SDL_AudioSpec));

#ifndef _WIN32

     err = pthread_sigmask (SIG_SETMASK, &old, NULL);