音频之Android NDK读写声卡

通过Android NDK读写声卡通过 AudioRecord和AudioTrack两个类实现。

AudioTrack：负责声音数据的输出
AudioRecord：负责声音数据的采集

相关头文件位置

system/media/audio/include/system
├── audio-base.h
├── audio-base-utils.h
├── audio_effect-base.h
├── audio_effect.h
├── audio_effects
├── audio.h
├── audio_policy.h
└── sound_trigger.h

音频源：
typedef enum {
AUDIO_SOURCE_DEFAULT = 0, //默认输入源
AUDIO_SOURCE_MIC = 1, //Microphone audio source 麦克风输入源
AUDIO_SOURCE_VOICE_UPLINK = 2, //Voice call uplink (Tx) audio source 语音呼叫上行(Tx)输入源
AUDIO_SOURCE_VOICE_DOWNLINK = 3, //Voice call downlink (Rx) audio source 语音呼叫下行(Rx)输入源
AUDIO_SOURCE_VOICE_CALL = 4, //Voice call uplink + downlink audio source 语音呼叫上下行输入源
AUDIO_SOURCE_CAMCORDER = 5, //Microphone audio source tuned for video recording 视频录制的麦克风音频源
AUDIO_SOURCE_VOICE_RECOGNITION = 6, //Microphone audio source tuned for voice recognition 针对语音唤醒的输入源
AUDIO_SOURCE_VOICE_COMMUNICATION = 7, //Microphone audio source tuned for voice communications such as VoIP 针对VOIP语音的输入源
AUDIO_SOURCE_REMOTE_SUBMIX = 8,
AUDIO_SOURCE_UNPROCESSED = 9,
AUDIO_SOURCE_VOICE_PERFORMANCE = 10,
AUDIO_SOURCE_ECHO_REFERENCE = 1997,
AUDIO_SOURCE_FM_TUNER = 1998,
#ifndef AUDIO_NO_SYSTEM_DECLARATIONS
/**
* A low-priority, preemptible audio source for for background software
* hotword detection. Same tuning as VOICE_RECOGNITION.
* Used only internally by the framework.
*/
AUDIO_SOURCE_HOTWORD = 1999,
#endif // AUDIO_NO_SYSTEM_DECLARATIONS
} audio_source_t;

typedef enum {
AUDIO_SESSION_OUTPUT_STAGE = -1, // (-1)
AUDIO_SESSION_OUTPUT_MIX = 0,
AUDIO_SESSION_ALLOCATE = 0,
AUDIO_SESSION_NONE = 0,
} audio_session_t;

//音频格式
typedef enum {//省略部分定义
AUDIO_FORMAT_INVALID = 0xFFFFFFFFu,
AUDIO_FORMAT_DEFAULT = 0,
AUDIO_FORMAT_PCM = 0x00000000u,
AUDIO_FORMAT_MP3 = 0x01000000u,
AUDIO_FORMAT_AMR_NB = 0x02000000u,
/* Subformats */
AUDIO_FORMAT_PCM_SUB_16_BIT = 0x1u,
AUDIO_FORMAT_PCM_SUB_8_BIT = 0x2u,
AUDIO_FORMAT_PCM_SUB_32_BIT = 0x3u,
AUDIO_FORMAT_PCM_SUB_8_24_BIT = 0x4u,
AUDIO_FORMAT_PCM_SUB_FLOAT = 0x5u,
AUDIO_FORMAT_PCM_SUB_24_BIT_PACKED = 0x6u,

/* Aliases */
AUDIO_FORMAT_PCM_16_BIT = 0x1u, // (PCM | PCM_SUB_16_BIT) //PCM16位
AUDIO_FORMAT_PCM_8_BIT = 0x2u, // (PCM | PCM_SUB_8_BIT) //PCM 8位
AUDIO_FORMAT_PCM_32_BIT = 0x3u, // (PCM | PCM_SUB_32_BIT)
AUDIO_FORMAT_PCM_8_24_BIT = 0x4u, // (PCM | PCM_SUB_8_24_BIT)
AUDIO_FORMAT_PCM_FLOAT = 0x5u, // (PCM | PCM_SUB_FLOAT)
AUDIO_FORMAT_PCM_24_BIT_PACKED = 0x6u, // (PCM | PCM_SUB_24_BIT_PACKED)
AUDIO_FORMAT_AAC_MAIN = 0x4000001u, // (AAC | AAC_SUB_MAIN)
AUDIO_FORMAT_AAC_LC = 0x4000002u, // (AAC | AAC_SUB_LC)
AUDIO_FORMAT_AAC_SSR = 0x4000004u, // (AAC | AAC_SUB_SSR)

} audio_format_t;

enum {//省略部分定义
AUDIO_CHANNEL_REPRESENTATION_POSITION = 0x0u,
AUDIO_CHANNEL_REPRESENTATION_INDEX = 0x2u,
AUDIO_CHANNEL_NONE = 0x0u,
AUDIO_CHANNEL_INVALID = 0xC0000000u,

AUDIO_CHANNEL_OUT_FRONT_LEFT = 0x1u,
AUDIO_CHANNEL_OUT_FRONT_RIGHT = 0x2u,
AUDIO_CHANNEL_IN_TOP_RIGHT = 0x400000u,
AUDIO_CHANNEL_IN_VOICE_UPLINK = 0x4000u,
AUDIO_CHANNEL_IN_VOICE_DNLINK = 0x8000u,
AUDIO_CHANNEL_IN_MONO = 0x10u, // IN_FRONT //单声道
AUDIO_CHANNEL_IN_STEREO = 0xCu, // IN_LEFT | IN_RIGHT 立体声
AUDIO_CHANNEL_IN_FRONT_BACK = 0x30u, // IN_FRONT | IN_BACK
AUDIO_CHANNEL_IN_6 = 0xFCu, // IN_LEFT | IN_RIGHT | IN_FRONT | IN_BACK | IN_LEFT_PROCESSED | IN_RIGHT_PROCESSED
AUDIO_CHANNEL_IN_2POINT0POINT2 = 0x60000Cu, // IN_LEFT | IN_RIGHT | IN_TOP_LEFT | IN_TOP_RIGHT
AUDIO_CHANNEL_IN_2POINT1POINT2 = 0x70000Cu, // IN_LEFT | IN_RIGHT | IN_TOP_LEFT | IN_TOP_RIGHT | IN_LOW_FREQUENCY
AUDIO_CHANNEL_IN_3POINT0POINT2 = 0x64000Cu, // IN_LEFT | IN_CENTER | IN_RIGHT | IN_TOP_LEFT | IN_TOP_RIGHT
AUDIO_CHANNEL_IN_3POINT1POINT2 = 0x74000Cu, // IN_LEFT | IN_CENTER | IN_RIGHT | IN_TOP_LEFT | IN_TOP_RIGHT | IN_LOW_FREQUENCY
AUDIO_CHANNEL_IN_5POINT1 = 0x17000Cu, // IN_LEFT | IN_CENTER | IN_RIGHT | IN_BACK_LEFT | IN_BACK_RIGHT | IN_LOW_FREQUENCY
AUDIO_CHANNEL_IN_VOICE_UPLINK_MONO = 0x4010u, // IN_VOICE_UPLINK | IN_MONO
AUDIO_CHANNEL_IN_VOICE_DNLINK_MONO = 0x8010u, // IN_VOICE_DNLINK | IN_MONO
AUDIO_CHANNEL_IN_VOICE_CALL_MONO = 0xC010u, // IN_VOICE_UPLINK_MONO | IN_VOICE_DNLINK_MONO
};

typedef enum {
AUDIO_INPUT_FLAG_NONE = 0x0,
AUDIO_INPUT_FLAG_FAST = 0x1,
AUDIO_INPUT_FLAG_HW_HOTWORD = 0x2,
AUDIO_INPUT_FLAG_RAW = 0x4,
AUDIO_INPUT_FLAG_SYNC = 0x8,
AUDIO_INPUT_FLAG_MMAP_NOIRQ = 0x10,
AUDIO_INPUT_FLAG_VOIP_TX = 0x20,
AUDIO_INPUT_FLAG_HW_AV_SYNC = 0x40,
#ifndef AUDIO_NO_SYSTEM_DECLARATIONS // TODO: Expose at HAL interface, remove FRAMEWORK_FLAGS mask
AUDIO_INPUT_FLAG_DIRECT = 0x80,
AUDIO_INPUT_FRAMEWORK_FLAGS = AUDIO_INPUT_FLAG_DIRECT,
#endif
} audio_input_flags_t;

enum {
AUDIO_IO_HANDLE_NONE = 0,
AUDIO_MODULE_HANDLE_NONE = 0,
AUDIO_PORT_HANDLE_NONE = 0,
AUDIO_PATCH_HANDLE_NONE = 0,
};

TRANSFER_CALLBACK   通过回调函数传输数据
TRANSFER_OBTAIN
TRANSFER_SYNC
TRANSFER_DEFAULT

demo源码：

├── Android.mk
├── include
└── src
└── audio_main.cpp

audio_main.cpp:

#include <stdio.h>
#include <pthread.h>
#include <math.h>
#include <system/audio.h>
#include <media/AudioRecord.h>
#include <media/AudioTrack.h>using namespace android;sp<AudioRecord> mAudioRecord;
sp<AudioTrack> mAudioTrack;
FILE *g_read_pcm = NULL;
FILE *g_write_pcm = NULL;
audio_channel_mask_t channelmask = AUDIO_CHANNEL_IN_MONO;
audio_format_t audio_format = AUDIO_FORMAT_PCM_16_BIT;
int sample_rate = 16000;
int min_buf_size = 0;void read_audio_data(int event, void *user, void *info)
{if (event != AudioRecord::EVENT_MORE_DATA) {printf("%s: event: %d\n", __FUNCTION__, event);return;}AudioRecord::Buffer *buffer = static_cast<AudioRecord::Buffer *>(info);if (buffer->size == 0) {return;}//printf("%s: buf size: %d\n", __FUNCTION__, buffer->size);fwrite(buffer->raw, buffer->size, 1, g_write_pcm);
}//read from soundcard and write into file
int ndk_audio_read()
{int ret = 0;char file[256] = {'\0'};size_t frame_count = 0;int frame_size = 0;String16  strName = String16("reader");mAudioRecord = new AudioRecord(strName);mAudioRecord.get();status_t result = AudioRecord::getMinFrameCount(&frame_count, sample_rate,audio_format, channelmask);if (result == NO_ERROR) {int channel_count = popcount(channelmask);min_buf_size = frame_count * channel_count * (audio_format == AUDIO_FORMAT_PCM_16_BIT ? 2 : 1);} else if (result == BAD_VALUE) {printf("Invalid param when get min frame count\n");return -1;} else {printf("Faield to get min frame count\n");return -1;}min_buf_size *= 2;// To prevent "buffer overflow" issueif (min_buf_size > 0) {printf("get min buf size[%d]\n", min_buf_size);} else {printf("get min buf size failed\n");return -1;}frame_size = popcount(channelmask) * (audio_format == AUDIO_FORMAT_PCM_16_BIT ? 2 : 1);frame_count = min_buf_size / frame_size;ret = mAudioRecord->set(AUDIO_SOURCE_MIC,sample_rate,audio_format,channelmask,frame_count,read_audio_data,NULL,0,false,AUDIO_SESSION_ALLOCATE,AudioRecord::TRANSFER_CALLBACK,AUDIO_INPUT_FLAG_FAST,getuid(),getpid(),NULL,AUDIO_PORT_HANDLE_NONE);if (ret != NO_ERROR) {printf("AudioRecord set failure\n");return -1;}else{printf("set success\n");}if (mAudioRecord->initCheck() != NO_ERROR) {printf("AudioRecord initialization failed!");return -1;}snprintf(file, 256, "/data/ndksound.pcm");g_write_pcm = fopen(file, "wb");ret = mAudioRecord->start();if (ret != NO_ERROR) {printf("Audio Record start failure ret: [%d]", ret);}return 0;
}void write_audio_data(int event, void *user, void *info)
{if (event != AudioTrack::EVENT_MORE_DATA) {printf("soundcard writer event: %d\n", event);return;}AudioTrack::Buffer *buffer = static_cast<AudioTrack::Buffer *>(info);if (buffer->size == 0) {return;}memset(buffer->raw, 0, buffer->size);int ret = fread(buffer->raw, 1, buffer->size, g_read_pcm);if (ret <= 0) {printf("%s: no more data:%d\n", __FUNCTION__, ret);exit(1);}
}//read from file and write into soundcard
int ndk_audio_write()
{int ret = 0;char file[256] = {'\0'};size_t frame_count = 0;int frame_size = 0;mAudioTrack = new AudioTrack();mAudioTrack.get();status_t result = AudioTrack::getMinFrameCount(&frame_count, AUDIO_STREAM_DEFAULT,sample_rate);if (result == NO_ERROR) {int channel_count = popcount(channelmask);min_buf_size = frame_count * channel_count * (audio_format == AUDIO_FORMAT_PCM_16_BIT ? 2 : 1);} else if (result == BAD_VALUE) {printf("Invalid param when get min frame count\n");return -1;} else {printf("Faield to get min frame count\n");return -1;}if (min_buf_size > 0) {printf("get min buf size[%d]\n", min_buf_size);} else {printf("get min buf size failed\n");return -1;}channelmask = AUDIO_CHANNEL_OUT_MONO;frame_size = popcount(channelmask) * (audio_format == AUDIO_FORMAT_PCM_16_BIT ? 2 : 1);frame_count = min_buf_size / frame_size;ret = mAudioTrack->set(AUDIO_STREAM_VOICE_CALL,sample_rate,audio_format,channelmask,frame_count,AUDIO_OUTPUT_FLAG_FAST,write_audio_data,NULL,0,0,false,AUDIO_SESSION_ALLOCATE,AudioTrack::TRANSFER_CALLBACK,NULL,-1);if (ret != NO_ERROR) {printf("mAudioTrack set failure\n");return -1;}else{printf("set success\n");}if (mAudioTrack->initCheck() != NO_ERROR) {printf("mAudioTrack initialization failed!");return -1;}snprintf(file, 256, "/data/ndksound.pcm");g_read_pcm = fopen(file, "rb");if (!g_read_pcm) {printf("open file failed\n");return -1;}ret = mAudioTrack->start();if (ret != NO_ERROR) {printf("Audio Track start failure ret: [%d]", ret);return -1;}printf("start success\n");return 0;
}int main(int argc, char *argv[])
{int ret = 0;if (argc < 2) {printf("need 2 param\n");return -1;}if (0 == strcmp(argv[1], "read")) {printf("read soundcard\n");ret = ndk_audio_read();if (ret < 0) {exit(1);}} else {printf("write soundcard\n");ret = ndk_audio_write();if (ret < 0) {exit(1);}}while (1) {sleep(5);}if (g_read_pcm) {fclose(g_read_pcm);}if (g_write_pcm) {fclose(g_write_pcm);}return 0;
}

Android.mk

LOCAL_PATH := $(call my-dir)
include $(CLEAR_VARS)LOCAL_SRC_FILES += \src/audio_main.cppLOCAL_C_INCLUDES += \bionic \external/stlport/stlport \external/libcxx/include \frameworks/av/include \frameworks/av/media/libaudioclient/include \frameworks/native/libs/nativebase/include \frameworks/native/libs/math/include \frameworks/av/media/ndk/include \system/core/include \system/core/libprocessgroup/include \system/core/base/include \system/core/libutils/include \LOCAL_CFLAGS := -DANDROID -Wall -Wno-implicit-function-declaration  -Wl,--unresolved-symbols=ignore-allLOCAL_MODULE := ndk_audio
LOCAL_LDLIBS := -lm -lmediandk -landroid -laudioclient -lstdc++ -lutilsinclude $(BUILD_EXECUTABLE)

demo运行

从声卡读声音数据写到文件： ./ndk_audio read

从文件读声音数据写到声卡： ./ndk_audio write

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