Add support for pitch shifting.

This commit should bring the mini_al backend up to feature parity with
the OpenAL backend.

1 files changed, 84 insertions, 9 deletions

diff --git a/src/external/mini_al.h b/src/external/mini_al.h
index 58f542cf..fad9952f 100644
--- a/src/external/mini_al.h
+++ b/src/external/mini_al.h
@@ -570,7 +570,6 @@ struct mal_src
     mal_src_config config;
     mal_src_read_proc onRead;
     void* pUserData;
-    float ratio;
     float bin[256];
     mal_src_cache cache;    // <-- For simplifying and optimizing client -> memory reading.
 
@@ -1353,6 +1352,12 @@ static inline mal_device_config mal_device_config_init_playback(mal_format forma
 // Initializes a sample rate conversion object.
 mal_result mal_src_init(mal_src_config* pConfig, mal_src_read_proc onRead, void* pUserData, mal_src* pSRC);
 
+// Dynamically adjusts the output sample rate.
+//
+// This is useful for dynamically adjust pitch. Keep in mind, however, that this will speed up or slow down the sound. If this
+// is not acceptable you will need to use your own algorithm.
+mal_result mal_src_set_output_sample_rate(mal_src* pSRC, mal_uint32 sampleRateOut);
+
 // Reads a number of frames.
 //
 // Returns the number of frames actually read.
@@ -1376,6 +1381,12 @@ mal_uint32 mal_src_read_frames_ex(mal_src* pSRC, mal_uint32 frameCount, void* pF
 // Initializes a DSP object.
 mal_result mal_dsp_init(mal_dsp_config* pConfig, mal_dsp_read_proc onRead, void* pUserData, mal_dsp* pDSP);
 
+// Dynamically adjusts the output sample rate.
+//
+// This is useful for dynamically adjust pitch. Keep in mind, however, that this will speed up or slow down the sound. If this
+// is not acceptable you will need to use your own algorithm.
+mal_result mal_dsp_set_output_sample_rate(mal_dsp* pDSP, mal_uint32 sampleRateOut);
+
 // Reads a number of frames and runs them through the DSP processor.
 //
 // This this _not_ flush the internal buffers which means you may end up with a few less frames than you may expect. Look at
@@ -9313,21 +9324,27 @@ mal_result mal_src_init(mal_src_config* pConfig, mal_src_read_proc onRead, void*
     pSRC->onRead = onRead;
     pSRC->pUserData = pUserData;
 
-    // If the in and out sample rates are the same, fall back to the passthrough algorithm.
-    if (pSRC->config.sampleRateIn == pSRC->config.sampleRateOut) {
-        pSRC->config.algorithm = mal_src_algorithm_none;
-    }
-
     if (pSRC->config.cacheSizeInFrames > MAL_SRC_CACHE_SIZE_IN_FRAMES || pSRC->config.cacheSizeInFrames == 0) {
         pSRC->config.cacheSizeInFrames = MAL_SRC_CACHE_SIZE_IN_FRAMES;
     }
 
-    pSRC->ratio = (float)pSRC->config.sampleRateIn / pSRC->config.sampleRateOut;
-
     mal_src_cache_init(pSRC, &pSRC->cache);
     return MAL_SUCCESS;
 }
 
+mal_result mal_src_set_output_sample_rate(mal_src* pSRC, mal_uint32 sampleRateOut)
+{
+    if (pSRC == NULL) return MAL_INVALID_ARGS;
+
+    // Must have a sample rate of > 0.
+    if (sampleRateOut == 0) {
+        return MAL_INVALID_ARGS;
+    }
+
+    pSRC->config.sampleRateOut = sampleRateOut;
+    return MAL_SUCCESS;
+}
+
 mal_uint32 mal_src_read_frames(mal_src* pSRC, mal_uint32 frameCount, void* pFramesOut)
 {
     return mal_src_read_frames_ex(pSRC, frameCount, pFramesOut, MAL_FALSE);
@@ -9337,6 +9354,13 @@ mal_uint32 mal_src_read_frames_ex(mal_src* pSRC, mal_uint32 frameCount, void* pF
 {
     if (pSRC == NULL || frameCount == 0 || pFramesOut == NULL) return 0;
 
+    mal_src_algorithm algorithm = pSRC->config.algorithm;
+
+    // Always use passthrough if the sample rates are the same.
+    if (pSRC->config.sampleRateIn == pSRC->config.sampleRateOut) {
+        algorithm = mal_src_algorithm_none;
+    }
+
     // Could just use a function pointer instead of a switch for this...
     switch (pSRC->config.algorithm)
     {
@@ -9408,7 +9432,7 @@ mal_uint32 mal_src_read_frames_linear(mal_src* pSRC, mal_uint32 frameCount, void
         pSRC->linear.isNextFramesLoaded = MAL_TRUE;
     }
 
-    float factor = pSRC->ratio;
+    float factor = (float)pSRC->config.sampleRateIn / pSRC->config.sampleRateOut;
 
     mal_uint32 totalFramesRead = 0;
     while (frameCount > 0) {
@@ -9995,6 +10019,57 @@ mal_result mal_dsp_init(mal_dsp_config* pConfig, mal_dsp_read_proc onRead, void*
     return MAL_SUCCESS;
 }
 
+mal_result mal_dsp_set_output_sample_rate(mal_dsp* pDSP, mal_uint32 sampleRateOut)
+{
+    if (pDSP == NULL) return MAL_INVALID_ARGS;
+
+    // Must have a sample rate of > 0.
+    if (sampleRateOut == 0) {
+        return MAL_INVALID_ARGS;
+    }
+
+    pDSP->config.sampleRateOut = sampleRateOut;
+
+    // If we already have an SRC pipeline initialized we do _not_ want to re-create it. Instead we adjust it. If we didn't previously
+    // have an SRC pipeline in place we'll need to initialize it.
+    if (pDSP->isSRCRequired) {
+        if (pDSP->config.sampleRateIn != pDSP->config.sampleRateOut) {
+            mal_src_set_output_sample_rate(&pDSP->src, sampleRateOut);
+        } else {
+            pDSP->isSRCRequired = MAL_FALSE;
+        }
+    } else {
+        // We may need a new SRC pipeline.
+        if (pDSP->config.sampleRateIn != pDSP->config.sampleRateOut) {
+            pDSP->isSRCRequired = MAL_TRUE;
+
+            mal_src_config srcConfig;
+            srcConfig.sampleRateIn      = pDSP->config.sampleRateIn;
+            srcConfig.sampleRateOut     = pDSP->config.sampleRateOut;
+            srcConfig.formatIn          = pDSP->config.formatIn;
+            srcConfig.formatOut         = mal_format_f32;
+            srcConfig.channels          = pDSP->config.channelsIn;
+            srcConfig.algorithm         = mal_src_algorithm_linear;
+            srcConfig.cacheSizeInFrames = pDSP->config.cacheSizeInFrames;
+            mal_result result = mal_src_init(&srcConfig, mal_dsp__src_on_read, pDSP, &pDSP->src);
+            if (result != MAL_SUCCESS) {
+                return result;
+            }
+        } else {
+            pDSP->isSRCRequired = MAL_FALSE;
+        }
+    }
+
+    // Update whether or not the pipeline is a passthrough.
+    if (pDSP->config.formatIn == pDSP->config.formatOut && pDSP->config.channelsIn == pDSP->config.channelsOut && pDSP->config.sampleRateIn == pDSP->config.sampleRateOut && !pDSP->isChannelMappingRequired) {
+        pDSP->isPassthrough = MAL_TRUE;
+    } else {
+        pDSP->isPassthrough = MAL_FALSE;
+    }
+
+    return MAL_SUCCESS;
+}
+
 mal_uint32 mal_dsp_read_frames(mal_dsp* pDSP, mal_uint32 frameCount, void* pFramesOut)
 {
     return mal_dsp_read_frames_ex(pDSP, frameCount, pFramesOut, MAL_FALSE);