Fixed SDL 1.2 compatibility problem.

The API specifies that SDL_OpenAudio() will fill out the 'desired' audio spec
with the correct samples and size set by the driver.  This value is important
since it may be used by applications that size audio buffers, etc.

However, we want to allow advanced applications to call SDL_OpenAudioDevice()
which gets passed a const 'desired' parameter, and have the correct data filled
into the 'obtained' parameter, possibly allowing or not allowing format changes.

So... 'obtained' becomes the audio format the user callback is expected to use,
and we add flags to allow the application to specify which format changes are
allowed.

Note: We really need to add a way to query the 'obtained' audio spec.

--HG--
extra : convert_revision : svn%3Ac70aab31-4412-0410-b14c-859654838e24/trunk%403328

include/SDL_audio.h

@@ -129,6 +129,11 @@ typedef struct SDL_AudioSpec
 #define AUDIO_F32SYS	AUDIO_F32MSB
 #endif
 
+/* Which audio format changes are allowed when opening a device */
+#define SDL_AUDIO_ALLOW_FREQUENCY_CHANGE    0x00000001
+#define SDL_AUDIO_ALLOW_FORMAT_CHANGE       0x00000002
+#define SDL_AUDIO_ALLOW_CHANNELS_CHANGE     0x00000004
+#define SDL_AUDIO_ALLOW_ANY_CHANGE          (SDL_AUDIO_ALLOW_FREQUENCY_CHANGE|SDL_AUDIO_ALLOW_FORMAT_CHANGE|SDL_AUDIO_ALLOW_CHANNELS_CHANGE)
 
 /* A structure to hold a set of audio conversion filters and buffers */
 struct SDL_AudioCVT;
@@ -217,7 +222,7 @@ extern DECLSPEC const char *SDLCALL SDL_GetCurrentAudioDriver(void);
  * may modify the requested size of the audio buffer, you should allocate
  * any local mixing buffers after you open the audio device.
  */
-extern DECLSPEC int SDLCALL SDL_OpenAudio(const SDL_AudioSpec * desired,
+extern DECLSPEC int SDLCALL SDL_OpenAudio(SDL_AudioSpec * desired,
                                           SDL_AudioSpec * obtained);
 
 /*
@@ -277,7 +282,9 @@ extern DECLSPEC SDL_AudioDeviceID SDLCALL SDL_OpenAudioDevice(const char
                                                               SDL_AudioSpec *
                                                               desired,
                                                               SDL_AudioSpec *
-                                                              obtained);
+                                                              obtained,
+                                                              int
+                                                              allowed_changes);
 
 
 

src/audio/SDL_audio.c

@@ -792,12 +792,13 @@ prepare_audiospec(const SDL_AudioSpec * orig, SDL_AudioSpec * prepared)
 
 static SDL_AudioDeviceID
 open_audio_device(const char *devname, int iscapture,
-                  const SDL_AudioSpec * _desired, SDL_AudioSpec * obtained,
-                  int min_id)
+                  const SDL_AudioSpec * desired, SDL_AudioSpec * obtained,
+                  int allowed_changes, int min_id)
 {
     SDL_AudioDeviceID id = 0;
-    SDL_AudioSpec desired;
+    SDL_AudioSpec _obtained;
     SDL_AudioDevice *device;
+    SDL_bool build_cvt;
     int i = 0;
 
     if (!SDL_WasInit(SDL_INIT_AUDIO)) {
@@ -810,7 +811,10 @@ open_audio_device(const char *devname, int iscapture,
         return 0;
     }
 
-    if (!prepare_audiospec(_desired, &desired)) {
+    if (!obtained) {
+        obtained = &_obtained;
+    }
+    if (!prepare_audiospec(desired, obtained)) {
         return 0;
     }
 
@@ -865,7 +869,7 @@ open_audio_device(const char *devname, int iscapture,
         return 0;
     }
     SDL_memset(device, '\0', sizeof(SDL_AudioDevice));
-    SDL_memcpy(&device->spec, &desired, sizeof(SDL_AudioSpec));
+    device->spec = *obtained;
     device->enabled = 1;
     device->paused = 1;
     device->iscapture = iscapture;
@@ -886,12 +890,6 @@ open_audio_device(const char *devname, int iscapture,
     }
     device->opened = 1;
 
-    /* If the audio driver changes the buffer size, accept it */
-    if (device->spec.samples != desired.samples) {
-        desired.samples = device->spec.samples;
-        SDL_CalculateAudioSpec(&device->spec);
-    }
-
     /* Allocate a fake audio memory buffer */
     device->fake_stream = SDL_AllocAudioMem(device->spec.size);
     if (device->fake_stream == NULL) {
@@ -900,23 +898,47 @@ open_audio_device(const char *devname, int iscapture,
         return 0;
     }
 
+    /* If the audio driver changes the buffer size, accept it */
+    if (device->spec.samples != obtained->samples) {
+        obtained->samples = device->spec.samples;
+        SDL_CalculateAudioSpec(obtained);
+    }
+
     /* See if we need to do any conversion */
-    if (obtained != NULL) {
-        SDL_memcpy(obtained, &device->spec, sizeof(SDL_AudioSpec));
-    } else if (desired.freq != device->spec.freq ||
-               desired.format != device->spec.format ||
-               desired.channels != device->spec.channels) {
+    build_cvt = SDL_FALSE;
+    if (obtained->freq != device->spec.freq) {
+        if (allowed_changes & SDL_AUDIO_ALLOW_FREQUENCY_CHANGE) {
+            obtained->freq = device->spec.freq;
+        } else {
+            build_cvt = SDL_TRUE;
+        }
+    }
+    if (obtained->format != device->spec.format) {
+        if (allowed_changes & SDL_AUDIO_ALLOW_FORMAT_CHANGE) {
+            obtained->format = device->spec.format;
+        } else {
+            build_cvt = SDL_TRUE;
+        }
+    }
+    if (obtained->channels != device->spec.channels) {
+        if (allowed_changes & SDL_AUDIO_ALLOW_CHANNELS_CHANGE) {
+            obtained->channels = device->spec.channels;
+        } else {
+            build_cvt = SDL_TRUE;
+        }
+    }
+    if (build_cvt) {
         /* Build an audio conversion block */
         if (SDL_BuildAudioCVT(&device->convert,
-                              desired.format, desired.channels,
-                              desired.freq,
+                              obtained->format, obtained->channels,
+                              obtained->freq,
                               device->spec.format, device->spec.channels,
                               device->spec.freq) < 0) {
             close_audio_device(device);
             return 0;
         }
         if (device->convert.needed) {
-            device->convert.len = (int) (((double) desired.size) /
+            device->convert.len = (int) (((double) obtained->size) /
                                          device->convert.len_ratio);
 
             device->convert.buf =
@@ -966,7 +988,7 @@ open_audio_device(const char *devname, int iscapture,
 
 
 int
-SDL_OpenAudio(const SDL_AudioSpec * desired, SDL_AudioSpec * obtained)
+SDL_OpenAudio(SDL_AudioSpec * desired, SDL_AudioSpec * obtained)
 {
     SDL_AudioDeviceID id = 0;
 
@@ -983,7 +1005,12 @@ SDL_OpenAudio(const SDL_AudioSpec * desired, SDL_AudioSpec * obtained)
         return (-1);
     }
 
-    id = open_audio_device(NULL, 0, desired, obtained, 1);
+    if (obtained) {
+        id = open_audio_device(NULL, 0, desired, obtained,
+                               SDL_AUDIO_ALLOW_ANY_CHANGE, 1);
+    } else {
+        id = open_audio_device(NULL, 0, desired, desired, 0, 1);
+    }
     if (id > 1) {               /* this should never happen in theory... */
         SDL_CloseAudioDevice(id);
         SDL_SetError("Internal error"); /* MUST be Device ID #1! */
@@ -995,9 +1022,11 @@ SDL_OpenAudio(const SDL_AudioSpec * desired, SDL_AudioSpec * obtained)
 
 SDL_AudioDeviceID
 SDL_OpenAudioDevice(const char *device, int iscapture,
-                    const SDL_AudioSpec * desired, SDL_AudioSpec * obtained)
+                    const SDL_AudioSpec * desired, SDL_AudioSpec * obtained,
+                    int allowed_changes)
 {
-    return open_audio_device(device, iscapture, desired, obtained, 2);
+    return open_audio_device(device, iscapture, desired, obtained,
+                             allowed_changes, 2);
 }
 
 SDL_audiostatus