pipewire: Report correct device default formats instead of hardcoding Float32.

The comment in the source wasn't true; PipeWire doesn't _have_ to work in
float format. It presumably does if it has to mix, but if a game is the only
thing making noise on the system--a common scenario--then it might be able to
pass, say, Sint16 data straight through to the hardware without conversion.

Fixes #12129.

src/audio/pipewire/SDL_pipewire.c

@@ -513,6 +513,25 @@ static bool get_int_param(const struct spa_pod *param, Uint32 key, int *val)
     return false;
 }
 
+static SDL_AudioFormat SPAFormatToSDL(enum spa_audio_format spafmt)
+{
+    switch (spafmt) {
+        #define CHECKFMT(spa,sdl) case SPA_AUDIO_FORMAT_##spa: return SDL_AUDIO_##sdl
+        CHECKFMT(U8, U8);
+        CHECKFMT(S8, S8);
+        CHECKFMT(S16_LE, S16LE);
+        CHECKFMT(S16_BE, S16BE);
+        CHECKFMT(S32_LE, S32LE);
+        CHECKFMT(S32_BE, S32BE);
+        CHECKFMT(F32_LE, F32LE);
+        CHECKFMT(F32_BE, F32BE);
+        #undef CHECKFMT
+        default: break;
+    }
+
+    return SDL_AUDIO_UNKNOWN;
+}
+
 // Interface node callbacks
 static void node_event_info(void *object, const struct pw_node_info *info)
 {
@@ -541,6 +560,15 @@ static void node_event_param(void *object, int seq, uint32_t id, uint32_t index,
     struct node_object *node = object;
     struct io_node *io = node->userdata;
 
+    if ((id == SPA_PARAM_Format) && (io->spec.format == SDL_AUDIO_UNKNOWN)) {
+        struct spa_audio_info_raw info;
+        SDL_zero(info);
+        if (spa_format_audio_raw_parse(param, &info) == 0) {
+            //SDL_Log("Sink Format: %d, Rate: %d Hz, Channels: %d", info.format, info.rate, info.channels);
+            io->spec.format = SPAFormatToSDL(info.format);
+        }
+    }
+
     // Get the default frequency
     if (io->spec.freq == 0) {
         get_range_param(param, SPA_FORMAT_AUDIO_rate, &io->spec.freq, NULL, NULL);
@@ -672,7 +700,9 @@ static void registry_event_global_callback(void *object, uint32_t id, uint32_t p
                 // Begin setting the node properties
                 io->id = id;
                 io->recording = recording;
-                io->spec.format = SDL_AUDIO_F32; // Pipewire uses floats internally, other formats require conversion.
+                if (io->spec.format == SDL_AUDIO_UNKNOWN) {
+                    io->spec.format = SDL_AUDIO_S16;  // we'll go conservative here if for some reason the format isn't known.
+                }
                 io->name = io->buf;
                 io->path = io->buf + desc_buffer_len;
                 SDL_strlcpy(io->buf, node_desc, desc_buffer_len);