Add support for offsets to the low-level mixing API.

research/ma_mixing.h

@@ -599,7 +599,7 @@ ma_mixer_mix_pcm_frames()
 ma_mixer_begin()
 ma_mixer_end()
 */
-MA_API ma_result ma_mixer_mix_pcm_frames(ma_mixer* pMixer, const void* pFramesIn, ma_uint64 frameCountIn, float volume, ma_format formatIn, ma_uint32 channelsIn);
+MA_API ma_result ma_mixer_mix_pcm_frames(ma_mixer* pMixer, const void* pFramesIn, ma_uint64 offsetInFrames, ma_uint64 frameCountIn, float volume, ma_format formatIn, ma_uint32 channelsIn);
 
 /*
 Mixes audio data from a data source
@@ -645,9 +645,9 @@ See Also
 ma_mixer_begin()
 ma_mixer_end()
 */
-MA_API ma_result ma_mixer_mix_data_source(ma_mixer* pMixer, ma_data_source* pDataSource, ma_uint64 frameCountIn, ma_uint64* pFrameCountOut, float volume, ma_effect* pEffect, ma_bool32 loop);
-MA_API ma_result ma_mixer_mix_rb(ma_mixer* pMixer, ma_rb* pRB, ma_uint64 frameCountIn, ma_uint64* pFrameCountOut, float volume, ma_effect* pEffect, ma_format formatIn, ma_uint32 channelsIn); /* Caller is the consumer. */
-MA_API ma_result ma_mixer_mix_pcm_rb(ma_mixer* pMixer, ma_pcm_rb* pRB, ma_uint64 frameCountIn, ma_uint64* pFrameCountOut, float volume, ma_effect* pEffect);                                   /* Caller is the consumer. */
+MA_API ma_result ma_mixer_mix_data_source(ma_mixer* pMixer, ma_data_source* pDataSource, ma_uint64 offsetInFrames, ma_uint64 frameCountIn, ma_uint64* pFrameCountOut, float volume, ma_effect* pEffect, ma_bool32 loop);
+MA_API ma_result ma_mixer_mix_rb(ma_mixer* pMixer, ma_rb* pRB, ma_uint64 offsetInFrames, ma_uint64 frameCountIn, ma_uint64* pFrameCountOut, float volume, ma_effect* pEffect, ma_format formatIn, ma_uint32 channelsIn); /* Caller is the consumer. */
+MA_API ma_result ma_mixer_mix_pcm_rb(ma_mixer* pMixer, ma_pcm_rb* pRB, ma_uint64 offsetInFrames, ma_uint64 frameCountIn, ma_uint64* pFrameCountOut, float volume, ma_effect* pEffect);                                   /* Caller is the consumer. */
 
 MA_API ma_result ma_mixer_set_volume(ma_mixer* pMixer, float volume);
 MA_API ma_result ma_mixer_get_volume(ma_mixer* pMixer, float* pVolume);
@@ -2463,7 +2463,7 @@ MA_API ma_result ma_mixer_end(ma_mixer* pMixer, ma_mixer* pParentMixer, void* pF
     return MA_SUCCESS;
 }
 
-MA_API ma_result ma_mixer_mix_pcm_frames(ma_mixer* pMixer, const void* pFramesIn, ma_uint64 frameCountIn, float volume, ma_format formatIn, ma_uint32 channelsIn)
+MA_API ma_result ma_mixer_mix_pcm_frames(ma_mixer* pMixer, const void* pFramesIn, ma_uint64 offsetInFrames, ma_uint64 frameCountIn, float volume, ma_format formatIn, ma_uint32 channelsIn)
 {
     if (pMixer == NULL || pFramesIn == NULL) {
         return MA_INVALID_ARGS;
@@ -2473,16 +2473,16 @@ MA_API ma_result ma_mixer_mix_pcm_frames(ma_mixer* pMixer, const void* pFramesIn
         return MA_INVALID_ARGS; /* Passing in too many input frames. */
     }
 
-    ma_mix_pcm_frames(pMixer->pAccumulationBuffer, pFramesIn, frameCountIn, formatIn, channelsIn, volume);
+    ma_mix_pcm_frames(ma_offset_ptr(pMixer->pAccumulationBuffer, offsetInFrames * ma_get_accumulation_bytes_per_frame(pMixer->format, pMixer->channels)), pFramesIn, frameCountIn, formatIn, channelsIn, volume);
 
     return MA_SUCCESS;
 }
 
-static ma_result ma_mixer_mix_data_source_mmap(ma_mixer* pMixer, ma_data_source* pDataSource, ma_uint64 frameCountIn, ma_uint64* pFrameCountOut, float volume, ma_effect* pEffect, ma_format formatIn, ma_uint32 channelsIn, ma_bool32 loop)
+static ma_result ma_mixer_mix_data_source_mmap(ma_mixer* pMixer, ma_data_source* pDataSource, ma_uint64 offsetInFrames, ma_uint64 frameCountIn, ma_uint64* pFrameCountOut, float volume, ma_effect* pEffect, ma_format formatIn, ma_uint32 channelsIn, ma_bool32 loop)
 {
     ma_result result = MA_SUCCESS;
     ma_uint64 totalFramesProcessed = 0;
-    void* pRunningAccumulationBuffer = pMixer->pAccumulationBuffer;
+    void* pRunningAccumulationBuffer = NULL;
     ma_bool32 preEffectConversionRequired = MA_FALSE;
     ma_format effectFormatIn = ma_format_unknown;
     ma_uint32 effectChannelsIn = 0;
@@ -2496,10 +2496,13 @@ static ma_result ma_mixer_mix_data_source_mmap(ma_mixer* pMixer, ma_data_source*
         *pFrameCountOut = 0;
     }
 
-    if (frameCountIn > pMixer->mixingState.frameCountIn) {
+    if ((offsetInFrames + frameCountIn) > pMixer->mixingState.frameCountIn) {
         return MA_INVALID_ARGS; /* Passing in too many input frames. */
     }
 
+    /* Initially offset the accumulation buffer by the offset. */
+    pRunningAccumulationBuffer = ma_offset_ptr(pMixer->pAccumulationBuffer, offsetInFrames * ma_get_accumulation_bytes_per_frame(pMixer->format, pMixer->channels));
+
     if (pEffect != NULL) {
         /* We need to know the effect's input and output data format before we'll be able to apply it properly. */
         result = ma_effect_get_input_data_format(pEffect, &effectFormatIn, &effectChannelsIn, NULL);
@@ -2597,7 +2600,7 @@ static ma_result ma_mixer_mix_data_source_mmap(ma_mixer* pMixer, ma_data_source*
     return result;
 }
 
-static ma_result ma_mixer_mix_data_source_read(ma_mixer* pMixer, ma_data_source* pDataSource, ma_uint64 frameCountIn, ma_uint64* pFrameCountOut, float volume, ma_effect* pEffect, ma_format formatIn, ma_uint32 channelsIn, ma_bool32 loop)
+static ma_result ma_mixer_mix_data_source_read(ma_mixer* pMixer, ma_data_source* pDataSource, ma_uint64 offsetInFrames, ma_uint64 frameCountIn, ma_uint64* pFrameCountOut, float volume, ma_effect* pEffect, ma_format formatIn, ma_uint32 channelsIn, ma_bool32 loop)
 {
     ma_result result = MA_SUCCESS;
     ma_uint8  preMixBuffer[MA_DATA_CONVERTER_STACK_BUFFER_SIZE];
@@ -2617,7 +2620,7 @@ static ma_result ma_mixer_mix_data_source_read(ma_mixer* pMixer, ma_data_source*
         *pFrameCountOut = 0;
     }
 
-    if (frameCountIn > pMixer->mixingState.frameCountIn) {
+    if ((offsetInFrames + frameCountIn) > pMixer->mixingState.frameCountIn) {
         return MA_INVALID_ARGS; /* Passing in too many input frames. */
     }
 
@@ -2642,7 +2645,9 @@ static ma_result ma_mixer_mix_data_source_read(ma_mixer* pMixer, ma_data_source*
     preMixBufferCap = sizeof(preMixBuffer) / ma_get_bytes_per_frame(preMixFormat, preMixChannels);
 
     totalFramesProcessed = 0;
-    pRunningAccumulationBuffer = pMixer->pAccumulationBuffer;
+
+    /* Initially offset the accumulation buffer by the offset. */
+    pRunningAccumulationBuffer = ma_offset_ptr(pMixer->pAccumulationBuffer, offsetInFrames * ma_get_accumulation_bytes_per_frame(pMixer->format, pMixer->channels));
 
     while (totalFramesProcessed < frameCountIn) {
         ma_uint64 framesRead;
@@ -2714,7 +2719,7 @@ static ma_result ma_mixer_mix_data_source_read(ma_mixer* pMixer, ma_data_source*
     return result;
 }
 
-MA_API ma_result ma_mixer_mix_data_source(ma_mixer* pMixer, ma_data_source* pDataSource, ma_uint64 frameCountIn, ma_uint64* pFrameCountOut, float volume, ma_effect* pEffect, ma_bool32 loop)
+MA_API ma_result ma_mixer_mix_data_source(ma_mixer* pMixer, ma_data_source* pDataSource, ma_uint64 offsetInFrames, ma_uint64 frameCountIn, ma_uint64* pFrameCountOut, float volume, ma_effect* pEffect, ma_bool32 loop)
 {
     ma_result result;
     ma_format formatIn;
@@ -2738,10 +2743,10 @@ MA_API ma_result ma_mixer_mix_data_source(ma_mixer* pMixer, ma_data_source* pDat
 
     if (supportsMMap) {
         /* Fast path. This is memory mapping mode. */
-        return ma_mixer_mix_data_source_mmap(pMixer, pDataSourceCallbacks, frameCountIn, pFrameCountOut, volume, pEffect, formatIn, channelsIn, loop);
+        return ma_mixer_mix_data_source_mmap(pMixer, pDataSourceCallbacks, offsetInFrames, frameCountIn, pFrameCountOut, volume, pEffect, formatIn, channelsIn, loop);
     } else {
         /* Slow path. This is reading mode. */
-        return ma_mixer_mix_data_source_read(pMixer, pDataSourceCallbacks, frameCountIn, pFrameCountOut, volume, pEffect, formatIn, channelsIn, loop);
+        return ma_mixer_mix_data_source_read(pMixer, pDataSourceCallbacks, offsetInFrames, frameCountIn, pFrameCountOut, volume, pEffect, formatIn, channelsIn, loop);
     }
 }
 
@@ -2815,18 +2820,18 @@ static ma_result ma_rb_data_source_init(ma_rb* pRB, ma_format format, ma_uint32
     return MA_SUCCESS;
 }
 
-MA_API ma_result ma_mixer_mix_rb(ma_mixer* pMixer, ma_rb* pRB, ma_uint64 frameCountIn, ma_uint64* pFrameCountOut, float volume, ma_effect* pEffect, ma_format formatIn, ma_uint32 channelsIn)
+MA_API ma_result ma_mixer_mix_rb(ma_mixer* pMixer, ma_rb* pRB, ma_uint64 offsetInFrames, ma_uint64 frameCountIn, ma_uint64* pFrameCountOut, float volume, ma_effect* pEffect, ma_format formatIn, ma_uint32 channelsIn)
 {
     /* Ring buffer mixing can be implemented in terms of a memory mapped data source. */
     ma_rb_data_source ds;
     ma_rb_data_source_init(pRB, formatIn, channelsIn, &ds); /* Will never fail and does not require an uninit() implementation. */
 
-    return ma_mixer_mix_data_source(pMixer, &ds, frameCountIn, pFrameCountOut, volume, pEffect, MA_TRUE);   /* Ring buffers always loop, but the loop parameter will never actually be used because ma_rb_data_source__on_unmap() will never return MA_AT_END. */
+    return ma_mixer_mix_data_source(pMixer, &ds, offsetInFrames, frameCountIn, pFrameCountOut, volume, pEffect, MA_TRUE);   /* Ring buffers always loop, but the loop parameter will never actually be used because ma_rb_data_source__on_unmap() will never return MA_AT_END. */
 }
 
-MA_API ma_result ma_mixer_mix_pcm_rb(ma_mixer* pMixer, ma_pcm_rb* pRB, ma_uint64 frameCountIn, ma_uint64* pFrameCountOut, float volume, ma_effect* pEffect)
+MA_API ma_result ma_mixer_mix_pcm_rb(ma_mixer* pMixer, ma_pcm_rb* pRB, ma_uint64 offsetInFrames, ma_uint64 frameCountIn, ma_uint64* pFrameCountOut, float volume, ma_effect* pEffect)
 {
-    return ma_mixer_mix_rb(pMixer, &pRB->rb, frameCountIn, pFrameCountOut, volume, pEffect, pRB->format, pRB->channels);
+    return ma_mixer_mix_rb(pMixer, &pRB->rb, offsetInFrames, frameCountIn, pFrameCountOut, volume, pEffect, pRB->format, pRB->channels);
 }