Stereo downmixer supports generic configurations. Fix 7.1 downmix
Added a generic downmixer to stereo function to handle the
multichannel configurations not supported by the dedicated
downmix functions.
It first verifies the mask is supported, and then derives
channel indices for the downmix.
Added support for forcing the generic downmixer to be always
used instead of the format-specific functions (define
DOWNMIX_ALWAYS_USE_GENERIC_DOWNMIXER to force it).
Fixed 7.1 downmix function where handling of accumulate vs
overwrite was inversed.
Bug 4280902
Change-Id: I8259b32c4e90f76ef4dcd803592fc71df4ae90c5
diff --git a/media/libeffects/downmix/EffectDownmix.c b/media/libeffects/downmix/EffectDownmix.c
index f37cd5e..8735503 100644
--- a/media/libeffects/downmix/EffectDownmix.c
+++ b/media/libeffects/downmix/EffectDownmix.c
@@ -22,6 +22,11 @@
#include <stdbool.h>
#include "EffectDownmix.h"
+// Do not submit with DOWNMIX_TEST_CHANNEL_INDEX defined, strictly for testing
+//#define DOWNMIX_TEST_CHANNEL_INDEX 0
+// Do not submit with DOWNMIX_ALWAYS_USE_GENERIC_DOWNMIXER defined, strictly for testing
+//#define DOWNMIX_ALWAYS_USE_GENERIC_DOWNMIXER 0
+
#define MINUS_3_DB_IN_Q19_12 2896 // -3dB = 0.707 * 2^12 = 2896
typedef enum {
@@ -88,6 +93,67 @@
/*----------------------------------------------------------------------------
+ * Test code
+ *--------------------------------------------------------------------------*/
+#ifdef DOWNMIX_TEST_CHANNEL_INDEX
+// strictly for testing, logs the indices of the channels for a given mask,
+// uses the same code as Downmix_foldGeneric()
+void Downmix_testIndexComputation(uint32_t mask) {
+ ALOGI("Testing index computation for 0x%x:", mask);
+ // check against unsupported channels
+ if (mask & kUnsupported) {
+ ALOGE("Unsupported channels (top or front left/right of center)");
+ return;
+ }
+ // verify has FL/FR
+ if ((mask & AUDIO_CHANNEL_OUT_STEREO) != AUDIO_CHANNEL_OUT_STEREO) {
+ ALOGE("Front channels must be present");
+ return;
+ }
+ // verify uses SIDE as a pair (ok if not using SIDE at all)
+ bool hasSides = false;
+ if ((mask & kSides) != 0) {
+ if ((mask & kSides) != kSides) {
+ ALOGE("Side channels must be used as a pair");
+ return;
+ }
+ hasSides = true;
+ }
+ // verify uses BACK as a pair (ok if not using BACK at all)
+ bool hasBacks = false;
+ if ((mask & kBacks) != 0) {
+ if ((mask & kBacks) != kBacks) {
+ ALOGE("Back channels must be used as a pair");
+ return;
+ }
+ hasBacks = true;
+ }
+
+ const int numChan = popcount(mask);
+ const bool hasFC = ((mask & AUDIO_CHANNEL_OUT_FRONT_CENTER) == AUDIO_CHANNEL_OUT_FRONT_CENTER);
+ const bool hasLFE =
+ ((mask & AUDIO_CHANNEL_OUT_LOW_FREQUENCY) == AUDIO_CHANNEL_OUT_LOW_FREQUENCY);
+ const bool hasBC = ((mask & AUDIO_CHANNEL_OUT_BACK_CENTER) == AUDIO_CHANNEL_OUT_BACK_CENTER);
+ // compute at what index each channel is: samples will be in the following order:
+ // FL FR FC LFE BL BR BC SL SR
+ // when a channel is not present, its index is set to the same as the index of the preceding
+ // channel
+ const int indexFC = hasFC ? 2 : 1; // front center
+ const int indexLFE = hasLFE ? indexFC + 1 : indexFC; // low frequency
+ const int indexBL = hasBacks ? indexLFE + 1 : indexLFE; // back left
+ const int indexBR = hasBacks ? indexBL + 1 : indexBL; // back right
+ const int indexBC = hasBC ? indexBR + 1 : indexBR; // back center
+ const int indexSL = hasSides ? indexBC + 1 : indexBC; // side left
+ const int indexSR = hasSides ? indexSL + 1 : indexSL; // side right
+
+ ALOGI(" FL FR FC LFE BL BR BC SL SR");
+ ALOGI(" %d %d %d %d %d %d %d %d %d",
+ 0, 1, indexFC, indexLFE, indexBL, indexBR, indexBC, indexSL, indexSR);
+}
+#endif
+
+
+/*----------------------------------------------------------------------------
* Effect API implementation
*--------------------------------------------------------------------------*/
@@ -123,6 +189,26 @@
ALOGV("DownmixLib_Create()");
+#ifdef DOWNMIX_TEST_CHANNEL_INDEX
+ // should work (won't log an error)
+ ALOGI("DOWNMIX_TEST_CHANNEL_INDEX: should work:");
+ Downmix_testIndexComputation(AUDIO_CHANNEL_OUT_FRONT_LEFT | AUDIO_CHANNEL_OUT_FRONT_RIGHT |
+ AUDIO_CHANNEL_OUT_LOW_FREQUENCY | AUDIO_CHANNEL_OUT_BACK_CENTER);
+ Downmix_testIndexComputation(CHANNEL_MASK_QUAD_SIDE | CHANNEL_MASK_QUAD_BACK);
+ Downmix_testIndexComputation(CHANNEL_MASK_5POINT1_SIDE | AUDIO_CHANNEL_OUT_BACK_CENTER);
+ Downmix_testIndexComputation(CHANNEL_MASK_5POINT1_BACK | AUDIO_CHANNEL_OUT_BACK_CENTER);
+ // shouldn't work (will log an error, won't display channel indices)
+ ALOGI("DOWNMIX_TEST_CHANNEL_INDEX: should NOT work:");
+ Downmix_testIndexComputation(AUDIO_CHANNEL_OUT_FRONT_LEFT | AUDIO_CHANNEL_OUT_FRONT_RIGHT |
+ AUDIO_CHANNEL_OUT_LOW_FREQUENCY | AUDIO_CHANNEL_OUT_BACK_LEFT);
+ Downmix_testIndexComputation(AUDIO_CHANNEL_OUT_FRONT_LEFT | AUDIO_CHANNEL_OUT_FRONT_RIGHT |
+ AUDIO_CHANNEL_OUT_LOW_FREQUENCY | AUDIO_CHANNEL_OUT_SIDE_LEFT);
+ Downmix_testIndexComputation(AUDIO_CHANNEL_OUT_FRONT_LEFT |
+ AUDIO_CHANNEL_OUT_BACK_LEFT | AUDIO_CHANNEL_OUT_BACK_RIGHT);
+ Downmix_testIndexComputation(AUDIO_CHANNEL_OUT_FRONT_LEFT |
+ AUDIO_CHANNEL_OUT_SIDE_LEFT | AUDIO_CHANNEL_OUT_SIDE_RIGHT);
+#endif
+
if (pHandle == NULL || uuid == NULL) {
return -EINVAL;
}
@@ -232,6 +318,7 @@
const bool accumulate =
(pDwmModule->config.outputCfg.accessMode == EFFECT_BUFFER_ACCESS_ACCUMULATE);
+ const uint32_t downmixInputChannelMask = pDwmModule->config.inputCfg.channels;
switch(pDownmixer->type) {
@@ -256,8 +343,17 @@
break;
case DOWNMIX_TYPE_FOLD:
+#ifdef DOWNMIX_ALWAYS_USE_GENERIC_DOWNMIXER
+ // bypass the optimized downmix routines for the common formats
+ if (!Downmix_foldGeneric(
+ downmixInputChannelMask, pSrc, pDst, numFrames, accumulate)) {
+ ALOGE("Multichannel configuration 0x%x is not supported", downmixInputChannelMask);
+ return -EINVAL;
+ }
+ break;
+#endif
// optimize for the common formats
- switch((downmix_input_channel_mask_t)pDwmModule->config.inputCfg.channels) {
+ switch((downmix_input_channel_mask_t)downmixInputChannelMask) {
case CHANNEL_MASK_QUAD_BACK:
case CHANNEL_MASK_QUAD_SIDE:
Downmix_foldFromQuad(pSrc, pDst, numFrames, accumulate);
@@ -273,8 +369,11 @@
Downmix_foldFrom7Point1(pSrc, pDst, numFrames, accumulate);
break;
default:
- // FIXME implement generic downmix
- ALOGE("Multichannel configurations other than quad, 4.0, 5.1 and 7.1 are not supported");
+ if (!Downmix_foldGeneric(
+ downmixInputChannelMask, pSrc, pDst, numFrames, accumulate)) {
+ ALOGE("Multichannel configuration 0x%x is not supported", downmixInputChannelMask);
+ return -EINVAL;
+ }
break;
}
break;
@@ -707,6 +806,8 @@
* Inputs:
* pSrc quad audio samples to downmix
* numFrames the number of quad frames to downmix
+ * accumulate whether to mix (when true) the result of the downmix with the contents of pDst,
+ * or overwrite pDst (when false)
*
* Outputs:
* pDst downmixed stereo audio samples
@@ -751,6 +852,8 @@
* Inputs:
* pSrc surround signal to downmix
* numFrames the number of surround frames to downmix
+ * accumulate whether to mix (when true) the result of the downmix with the contents of pDst,
+ * or overwrite pDst (when false)
*
* Outputs:
* pDst downmixed stereo audio samples
@@ -763,6 +866,8 @@
// sample at index 1 is FR
// sample at index 2 is FC
// sample at index 3 is RC
+ // code is mostly duplicated between the two values of accumulate to avoid repeating the test
+ // for every sample
if (accumulate) {
while (numFrames) {
// centerPlusRearContrib = FC(-3dB) + RC(-3dB)
@@ -771,6 +876,7 @@
lt = (pSrc[0] << 12) + centerPlusRearContrib;
// FR + centerPlusRearContrib
rt = (pSrc[1] << 12) + centerPlusRearContrib;
+ // accumulate in destination
pDst[0] = clamp16(pDst[0] + (lt >> 12));
pDst[1] = clamp16(pDst[1] + (rt >> 12));
pSrc += 4;
@@ -785,8 +891,9 @@
lt = (pSrc[0] << 12) + centerPlusRearContrib;
// FR + centerPlusRearContrib
rt = (pSrc[1] << 12) + centerPlusRearContrib;
- pDst[0] = clamp16(lt >> 12);
- pDst[1] = clamp16(rt >> 12);
+ // store in destination
+ pDst[0] = clamp16(lt >> 12); // differs from when accumulate is true above
+ pDst[1] = clamp16(rt >> 12); // differs from when accumulate is true above
pSrc += 4;
pDst += 2;
numFrames--;
@@ -804,6 +911,8 @@
* Inputs:
* pSrc 5.1 audio samples to downmix
* numFrames the number of 5.1 frames to downmix
+ * accumulate whether to mix (when true) the result of the downmix with the contents of pDst,
+ * or overwrite pDst (when false)
*
* Outputs:
* pDst downmixed stereo audio samples
@@ -818,6 +927,8 @@
// sample at index 3 is LFE
// sample at index 4 is RL
// sample at index 5 is RR
+ // code is mostly duplicated between the two values of accumulate to avoid repeating the test
+ // for every sample
if (accumulate) {
while (numFrames) {
// centerPlusLfeContrib = FC(-3dB) + LFE(-3dB)
@@ -827,6 +938,7 @@
lt = (pSrc[0] << 12) + centerPlusLfeContrib + (pSrc[4] << 12);
// FR + centerPlusLfeContrib + RR
rt = (pSrc[1] << 12) + centerPlusLfeContrib + (pSrc[5] << 12);
+ // accumulate in destination
pDst[0] = clamp16(pDst[0] + (lt >> 12));
pDst[1] = clamp16(pDst[1] + (rt >> 12));
pSrc += 6;
@@ -842,8 +954,9 @@
lt = (pSrc[0] << 12) + centerPlusLfeContrib + (pSrc[4] << 12);
// FR + centerPlusLfeContrib + RR
rt = (pSrc[1] << 12) + centerPlusLfeContrib + (pSrc[5] << 12);
- pDst[0] = clamp16(lt >> 12);
- pDst[1] = clamp16(rt >> 12);
+ // store in destination
+ pDst[0] = clamp16(lt >> 12); // differs from when accumulate is true above
+ pDst[1] = clamp16(rt >> 12); // differs from when accumulate is true above
pSrc += 6;
pDst += 2;
numFrames--;
@@ -861,6 +974,8 @@
* Inputs:
* pSrc 7.1 audio samples to downmix
* numFrames the number of 7.1 frames to downmix
+ * accumulate whether to mix (when true) the result of the downmix with the contents of pDst,
+ * or overwrite pDst (when false)
*
* Outputs:
* pDst downmixed stereo audio samples
@@ -877,6 +992,8 @@
// sample at index 5 is RR
// sample at index 6 is SL
// sample at index 7 is SR
+ // code is mostly duplicated between the two values of accumulate to avoid repeating the test
+ // for every sample
if (accumulate) {
while (numFrames) {
// centerPlusLfeContrib = FC(-3dB) + LFE(-3dB)
@@ -886,8 +1003,9 @@
lt = (pSrc[0] << 12) + centerPlusLfeContrib + (pSrc[6] << 12) + (pSrc[4] << 12);
// FR + centerPlusLfeContrib + SR + RR
rt = (pSrc[1] << 12) + centerPlusLfeContrib + (pSrc[7] << 12) + (pSrc[5] << 12);
- pDst[0] = clamp16(lt >> 12);
- pDst[1] = clamp16(rt >> 12);
+ //accumulate in destination
+ pDst[0] = clamp16(pDst[0] + (lt >> 12));
+ pDst[1] = clamp16(pDst[1] + (rt >> 12));
pSrc += 8;
pDst += 2;
numFrames--;
@@ -901,8 +1019,9 @@
lt = (pSrc[0] << 12) + centerPlusLfeContrib + (pSrc[6] << 12) + (pSrc[4] << 12);
// FR + centerPlusLfeContrib + SR + RR
rt = (pSrc[1] << 12) + centerPlusLfeContrib + (pSrc[7] << 12) + (pSrc[5] << 12);
- pDst[0] = clamp16(pDst[0] + (lt >> 12));
- pDst[1] = clamp16(pDst[1] + (rt >> 12));
+ // store in destination
+ pDst[0] = clamp16(lt >> 12); // differs from when accumulate is true above
+ pDst[1] = clamp16(rt >> 12); // differs from when accumulate is true above
pSrc += 8;
pDst += 2;
numFrames--;
@@ -910,3 +1029,142 @@
}
}
+
+/*----------------------------------------------------------------------------
+ * Downmix_foldGeneric()
+ *----------------------------------------------------------------------------
+ * Purpose:
+ * downmix to stereo a multichannel signal whose format is:
+ * - has FL/FR
+ * - if using AUDIO_CHANNEL_OUT_SIDE*, it contains both left and right
+ * - if using AUDIO_CHANNEL_OUT_BACK*, it contains both left and right
+ * - doesn't use any of the AUDIO_CHANNEL_OUT_TOP* channels
+ * - doesn't use any of the AUDIO_CHANNEL_OUT_FRONT_*_OF_CENTER channels
+ * Only handles channel masks not enumerated in downmix_input_channel_mask_t
+ *
+ * Inputs:
+ * mask the channel mask of pSrc
+ * pSrc multichannel audio buffer to downmix
+ * numFrames the number of multichannel frames to downmix
+ * accumulate whether to mix (when true) the result of the downmix with the contents of pDst,
+ * or overwrite pDst (when false)
+ *
+ * Outputs:
+ * pDst downmixed stereo audio samples
+ *
+ * Returns: false if multichannel format is not supported
+ *
+ *----------------------------------------------------------------------------
+ */
+bool Downmix_foldGeneric(
+ uint32_t mask, int16_t *pSrc, int16_t*pDst, size_t numFrames, bool accumulate) {
+ // check against unsupported channels
+ if (mask & kUnsupported) {
+ ALOGE("Unsupported channels (top or front left/right of center)");
+ return false;
+ }
+ // verify has FL/FR
+ if ((mask & AUDIO_CHANNEL_OUT_STEREO) != AUDIO_CHANNEL_OUT_STEREO) {
+ ALOGE("Front channels must be present");
+ return false;
+ }
+ // verify uses SIDE as a pair (ok if not using SIDE at all)
+ bool hasSides = false;
+ if ((mask & kSides) != 0) {
+ if ((mask & kSides) != kSides) {
+ ALOGE("Side channels must be used as a pair");
+ return false;
+ }
+ hasSides = true;
+ }
+ // verify uses BACK as a pair (ok if not using BACK at all)
+ bool hasBacks = false;
+ if ((mask & kBacks) != 0) {
+ if ((mask & kBacks) != kBacks) {
+ ALOGE("Back channels must be used as a pair");
+ return false;
+ }
+ hasBacks = true;
+ }
+
+ const int numChan = popcount(mask);
+ const bool hasFC = ((mask & AUDIO_CHANNEL_OUT_FRONT_CENTER) == AUDIO_CHANNEL_OUT_FRONT_CENTER);
+ const bool hasLFE =
+ ((mask & AUDIO_CHANNEL_OUT_LOW_FREQUENCY) == AUDIO_CHANNEL_OUT_LOW_FREQUENCY);
+ const bool hasBC = ((mask & AUDIO_CHANNEL_OUT_BACK_CENTER) == AUDIO_CHANNEL_OUT_BACK_CENTER);
+ // compute at what index each channel is: samples will be in the following order:
+ // FL FR FC LFE BL BR BC SL SR
+ // when a channel is not present, its index is set to the same as the index of the preceding
+ // channel
+ const int indexFC = hasFC ? 2 : 1; // front center
+ const int indexLFE = hasLFE ? indexFC + 1 : indexFC; // low frequency
+ const int indexBL = hasBacks ? indexLFE + 1 : indexLFE; // back left
+ const int indexBR = hasBacks ? indexBL + 1 : indexBL; // back right
+ const int indexBC = hasBC ? indexBR + 1 : indexBR; // back center
+ const int indexSL = hasSides ? indexBC + 1 : indexBC; // side left
+ const int indexSR = hasSides ? indexSL + 1 : indexSL; // side right
+
+ int32_t lt, rt, centersLfeContrib; // samples in Q19.12 format
+ // code is mostly duplicated between the two values of accumulate to avoid repeating the test
+ // for every sample
+ if (accumulate) {
+ while (numFrames) {
+ // compute contribution of FC, BC and LFE
+ centersLfeContrib = 0;
+ if (hasFC) { centersLfeContrib += pSrc[indexFC]; }
+ if (hasLFE) { centersLfeContrib += pSrc[indexLFE]; }
+ if (hasBC) { centersLfeContrib += pSrc[indexBC]; }
+ centersLfeContrib *= MINUS_3_DB_IN_Q19_12;
+ // always has FL/FR
+ lt = (pSrc[0] << 12);
+ rt = (pSrc[1] << 12);
+ // mix in sides and backs
+ if (hasSides) {
+ lt += pSrc[indexSL] << 12;
+ rt += pSrc[indexSR] << 12;
+ }
+ if (hasBacks) {
+ lt += pSrc[indexBL] << 12;
+ rt += pSrc[indexBR] << 12;
+ }
+ lt += centersLfeContrib;
+ rt += centersLfeContrib;
+ // accumulate in destination
+ pDst[0] = clamp16(pDst[0] + (lt >> 12));
+ pDst[1] = clamp16(pDst[1] + (rt >> 12));
+ pSrc += numChan;
+ pDst += 2;
+ numFrames--;
+ }
+ } else {
+ while (numFrames) {
+ // compute contribution of FC, BC and LFE
+ centersLfeContrib = 0;
+ if (hasFC) { centersLfeContrib += pSrc[indexFC]; }
+ if (hasLFE) { centersLfeContrib += pSrc[indexLFE]; }
+ if (hasBC) { centersLfeContrib += pSrc[indexBC]; }
+ centersLfeContrib *= MINUS_3_DB_IN_Q19_12;
+ // always has FL/FR
+ lt = (pSrc[0] << 12);
+ rt = (pSrc[1] << 12);
+ // mix in sides and backs
+ if (hasSides) {
+ lt += pSrc[indexSL] << 12;
+ rt += pSrc[indexSR] << 12;
+ }
+ if (hasBacks) {
+ lt += pSrc[indexBL] << 12;
+ rt += pSrc[indexBR] << 12;
+ }
+ lt += centersLfeContrib;
+ rt += centersLfeContrib;
+ // store in destination
+ pDst[0] = clamp16(lt >> 12); // differs from when accumulate is true above
+ pDst[1] = clamp16(rt >> 12); // differs from when accumulate is true above
+ pSrc += numChan;
+ pDst += 2;
+ numFrames--;
+ }
+ }
+ return true;
+}
diff --git a/media/libeffects/downmix/EffectDownmix.h b/media/libeffects/downmix/EffectDownmix.h
index 4176b5a..be3ca3f 100644
--- a/media/libeffects/downmix/EffectDownmix.h
+++ b/media/libeffects/downmix/EffectDownmix.h
@@ -49,6 +49,17 @@
downmix_object_t context;
} downmix_module_t;
+const uint32_t kSides = AUDIO_CHANNEL_OUT_SIDE_LEFT | AUDIO_CHANNEL_OUT_SIDE_RIGHT;
+const uint32_t kBacks = AUDIO_CHANNEL_OUT_BACK_LEFT | AUDIO_CHANNEL_OUT_BACK_RIGHT;
+const uint32_t kUnsupported =
+ AUDIO_CHANNEL_OUT_FRONT_LEFT_OF_CENTER | AUDIO_CHANNEL_OUT_FRONT_RIGHT_OF_CENTER |
+ AUDIO_CHANNEL_OUT_TOP_CENTER |
+ AUDIO_CHANNEL_OUT_TOP_FRONT_LEFT |
+ AUDIO_CHANNEL_OUT_TOP_FRONT_CENTER |
+ AUDIO_CHANNEL_OUT_TOP_FRONT_RIGHT |
+ AUDIO_CHANNEL_OUT_TOP_BACK_LEFT |
+ AUDIO_CHANNEL_OUT_TOP_BACK_CENTER |
+ AUDIO_CHANNEL_OUT_TOP_BACK_RIGHT;
/*------------------------------------
* Effect API
@@ -92,5 +103,7 @@
void Downmix_foldFromSurround(int16_t *pSrc, int16_t*pDst, size_t numFrames, bool accumulate);
void Downmix_foldFrom5Point1(int16_t *pSrc, int16_t*pDst, size_t numFrames, bool accumulate);
void Downmix_foldFrom7Point1(int16_t *pSrc, int16_t*pDst, size_t numFrames, bool accumulate);
+bool Downmix_foldGeneric(
+ uint32_t mask, int16_t *pSrc, int16_t*pDst, size_t numFrames, bool accumulate);
#endif /*ANDROID_EFFECTDOWNMIX_H_*/