Merge "Add audio dithering for intermediate quantizations" into gingerbread (85e40799) · Commits · e / os / android_frameworks_base

media/libeffects/cyanogen-dsp/Effect.cpp

+2 −2

Original line number	Diff line number	Diff line
		@@ -65,7 +65,7 @@ int32_t Effect::command(uint32_t cmdCode, uint32_t cmdSize, void *pCmdData, uint
		switch (cmdCode) {
		case EFFECT_CMD_ENABLE:
		case EFFECT_CMD_DISABLE: {
		enable = cmdCode == EFFECT_CMD_ENABLE;
		mEnable = cmdCode == EFFECT_CMD_ENABLE;
		int32_t replyData = (int32_t ) pReplyData;
		*replyData = 0;
		break;
		@@ -110,7 +110,7 @@ int32_t Effect::command(uint32_t cmdCode, uint32_t cmdSize, void *pCmdData, uint

		int32_t Effect::process(audio_buffer_t in, audio_buffer_t out)
		{
		if (! enable) {
		if (! mEnable) {
		for (uint32_t i = 0; i < in->frameCount; i ++) {
		int32_t tmpL = read(in, i * 2);
		int32_t tmpR = read(in, i * 2 + 1);

+19 −5

Original line number	Diff line number	Diff line
		@@ -3,6 +3,12 @@
		#include <stdint.h>
		#include <media/EffectApi.h>

		static inline uint16_t prng() {
		static uint32_t seed;
		seed = seed * 1664525 + 1013904223;
		return seed >> 14;
		}

		class Effect {
		private:
		audio_format_e mFormatIn;
		@@ -10,9 +16,18 @@ class Effect {
		effect_buffer_access_e mAccessMode;

		protected:
		bool enable;
		bool mEnable;
		float mSamplingRate;
		uint32_t mChannels;
		uint16_t mPreviousRandom;

		/* High-passed triangular probability density function. */
		inline int32_t triangularDither16() {
		uint16_t newRandom = prng();
		int32_t rnd = mPreviousRandom - newRandom;
		mPreviousRandom = newRandom;
		return rnd;
		}

		inline int32_t read(audio_buffer_t *in, int32_t idx) {
		switch (mFormatIn) {
		@@ -51,10 +66,9 @@ class Effect {
		}
		}

		/* I should probably apply dithering for S15 / U8. */
		switch (mFormatOut) {
		case SAMPLE_FORMAT_PCM_S15:
		sample >>= 8;
		sample = (sample + (triangularDither16() >> 8)) >> 8;
		if (sample > 32767) {
		sample = 32767;
		}
		@@ -65,7 +79,7 @@ class Effect {
		break;

		case SAMPLE_FORMAT_PCM_U8:
		sample >>= 16;
		sample = (sample + triangularDither16()) >> 16;
		sample += 128;
		if (sample > 255) {
		sample = 255;