Android Audio框架 audio_policy.conf文件

Android系统可以通过配置audio_policy.conf文件，来实现不同产品的差异化，audio_policy.conf文件中，配置了当前项目audio策略中支持的输入输出设备，对应的播放模式，采样率，采样精度，声道数等等。例如下面：

1 Primary {

2 sampling_rates 44100|48000

3 channel_masks AUDIO_CHANNEL_OUT_STEREO

4 formats AUDIO_FORMAT_PCM_16_BIT

6 flags AUDIO_OUTPUT_FLAG_PRIMARY

7 }

8 low_latency {

9 sampling_rates 44100|48000

10 channel_masks AUDIO_CHANNEL_OUT_STEREO

11 formats AUDIO_FORMAT_PCM_16_BIT

13 flags AUDIO_OUTPUT_FLAG_FAST

14 }

15 compress_offload {

16 sampling_rates 8000|11025|16000|22050|32000|44100|48000

17 channel_masks AUDIO_CHANNEL_OUT_MONO|AUDIO_CHANNEL_OUT_STEREO

18 formats AUDIO_FORMAT_MP3|AUDIO_FORMAT_AAC_LC|AUDIO_FORMAT_AAC_HE_V1|AUDIO_FORMAT_AAC_HE_V2

20 flags AUDIO_OUTPUT_FLAG_DIRECT|AUDIO_OUTPUT_FLAG_COMPRESS_OFFLOAD|AUDIO_OUTPUT_FLAG_NON_BLOCKING

21 }

1 a2dp {

2 outputs {

3 a2dp {

4 sampling_rates 44100

5 channel_masks AUDIO_CHANNEL_OUT_STEREO

6 formats AUDIO_FORMAT_PCM_16_BIT

7 devices AUDIO_DEVICE_OUT_ALL_A2DP

8 }

9 }

10 }

11 usb {

12 outputs {

13 usb_accessory {

14 sampling_rates 44100

15 channel_masks AUDIO_CHANNEL_OUT_STEREO

16 formats AUDIO_FORMAT_PCM_16_BIT

17 devices AUDIO_DEVICE_OUT_USB_ACCESSORY

18 }

19 usb_device {

20 sampling_rates dynamic

21 channel_masks dynamic

22 formats dynamic

23 devices AUDIO_DEVICE_OUT_USB_DEVICE

24 }

25 }

26 inputs {

27 usb_device {

28 sampling_rates dynamic

29 channel_masks AUDIO_CHANNEL_IN_STEREO

30 formats AUDIO_FORMAT_PCM_16_BIT

31 devices AUDIO_DEVICE_IN_USB_DEVICE

32 }

33 }

34 }

在AudioPolicyManager中会解析此文件，获取此信息，那什么时候会需要修改此文件呢，例如：如果所在项目没有听筒设备，所以在接听电话的时候需要默认切换到喇叭输出，这个时候就需要修改此文件，把听筒设备AUDIO_DEVICE_OUT_EARPIECE从所有场景下支持的输出设备中删除，这样的话，就会切换到默认输出设备喇叭下。这个文件的信息，也可以通过指令

adb shell dumpsys media.audio_policy 打印出来，如下：

1 HW Modules dump:

2 - HW Module 1:

3 - name: primary

4 - handle: 1

5 - version: 2.0

6 - outputs:

7 output 0:

8 - name: primary

9 - sampling rates: 44100, 48000

10 - channel masks: 0x0003

11 - formats: AUDIO_FORMAT_PCM_16_BIT

12 - flags: 0x0002

13 - devices:

14 Device 1:

15 - type: AUDIO_DEVICE_OUT_EARPIECE

16 Device 2:

17 - type: AUDIO_DEVICE_OUT_SPEAKER

18 Device 3:

19 - type: AUDIO_DEVICE_OUT_WIRED_HEADSET

20 Device 4:

21 - type: AUDIO_DEVICE_OUT_WIRED_HEADPHONE

22 Device 5:

23 - type: AUDIO_DEVICE_OUT_ALL_SCO

24 Device 6:

25 - type: AUDIO_DEVICE_OUT_PROXY

26 Device 7:

27 - type: AUDIO_DEVICE_OUT_AUX_DIGITAL

28 Device 8:

29 - type: AUDIO_DEVICE_OUT_ANLG_DOCK_HEADSET

30 Device 9:

31 - type: AUDIO_DEVICE_OUT_FM

32 Device 10:

33 - type: AUDIO_DEVICE_OUT_FM_TX

34 output 1:

35 - name: low_latency

36 - sampling rates: 44100, 48000

37 - channel masks: 0x0003

38 - formats: AUDIO_FORMAT_PCM_16_BIT

39 - flags: 0x0004

40 - devices:

41 Device 1:

42 - type: AUDIO_DEVICE_OUT_SPEAKER

43 Device 2:

44 - type: AUDIO_DEVICE_OUT_EARPIECE

45 Device 3:

46 - type: AUDIO_DEVICE_OUT_WIRED_HEADSET

47 Device 4:

48 - type: AUDIO_DEVICE_OUT_WIRED_HEADPHONE

49 Device 5:

50 - type: AUDIO_DEVICE_OUT_ALL_SCO

51 Device 6:

52 - type: AUDIO_DEVICE_OUT_AUX_DIGITAL

53 Device 7:

54 - type: AUDIO_DEVICE_OUT_PROXY

55 Device 8:

56 - type: AUDIO_DEVICE_OUT_ANLG_DOCK_HEADSET

57 Device 9:

58 - type: AUDIO_DEVICE_OUT_FM

59 Device 10:

在文件系统里，有两个地方存放此文件/system/etc/audio_policy.conf 和 /vendor/etc/audio_policy.conf，在创建AudioPolicyManager的时候会加载此配置文件：

1 AudioPolicyManager::AudioPolicyManager(AudioPolicyClientInterface *clientInterface)

2 {

3 /*将默认输出设备设置成SPEAKER*/

4 mDefaultOutputDevice = new DeviceDescriptor(String8(""), AUDIO_DEVICE_OUT_SPEAKER);

5 /*加载audio_policy.conf文件，先默认去加载vendor目录下的文件，如果找不到就去加载system目录下的*/

6 if (loadAudioPolicyConfig(AUDIO_POLICY_VENDOR_CONFIG_FILE) != NO_ERROR) {

7 if (loadAudioPolicyConfig(AUDIO_POLICY_CONFIG_FILE) != NO_ERROR) {

8 ALOGE("could not load audio policy configuration file, setting defaults");

9 /*如果两个目录都没有找到，就去加载一个默认的配置，默认的配置中会创建一个Primary module,

10 为它创建一个默认的输出设备speaker和默认输出设备主Mic.

11 */

12 defaultAudioPolicyConfig();

13 }

14 }

16 /*把所有的输入输出设备都会操作打开一遍，检查该设备是否是有效的*/

17 // open all output streams needed to access attached devices

18 audio_devices_t outputDeviceTypes = mAvailableOutputDevices.types();

19 audio_devices_t inputDeviceTypes = mAvailableInputDevices.types() & ~AUDIO_DEVICE_BIT_IN;

20 for (size_t i = 0; i < mHwModules.size(); i++) {

21 mHwModules[i]->mHandle = mpClientInterface->loadHwModule(mHwModules[i]->mName);

22 if (mHwModules[i]->mHandle == 0) {

23 ALOGW("could not open HW module %s", mHwModules[i]->mName);

24 continue;

25 }

26 // open all output streams needed to access attached devices

27 // except for direct output streams that are only opened when they are actually

28 // required by an app.

29 // This also validates mAvailableOutputDevices list

30 for (size_t j = 0; j < mHwModules[i]->mOutputProfiles.size(); j++)

31 {

32 const sp<IOProfile> outProfile = mHwModules[i]->mOutputProfiles[j];

34 if (outProfile->mSupportedDevices.isEmpty()) {

35 ALOGW("Output profile contains no device on module %s", mHwModules[i]->mName);

36 continue;

37 }

39 if ((outProfile->mFlags & AUDIO_OUTPUT_FLAG_DIRECT) != 0) {

40 continue;

41 }

42 audio_devices_t profileType = outProfile->mSupportedDevices.types();

43 if ((profileType & mDefaultOutputDevice->mDeviceType) != AUDIO_DEVICE_NONE) {

44 profileType = mDefaultOutputDevice->mDeviceType;

45 } else {

46 // chose first device present in mSupportedDevices also part of

47 // outputDeviceTypes

48 for (size_t k = 0; k < outProfile->mSupportedDevices.size(); k++) {

49 profileType = outProfile->mSupportedDevices[k]->mDeviceType;

50 if ((profileType & outputDeviceTypes) != 0) {

51 break;

52 }

53 }

54 }

55 if ((profileType & outputDeviceTypes) == 0) {

56 continue;

57 }

58 sp<AudioOutputDescriptor> outputDesc = new AudioOutputDescriptor(outProfile);

60 outputDesc->mDevice = profileType;

61 audio_config_t config = AUDIO_CONFIG_INITIALIZER;

62 config.sample_rate = outputDesc->mSamplingRate;

63 config.channel_mask = outputDesc->mChannelMask;

64 config.format = outputDesc->mFormat;

65 audio_io_handle_t output = AUDIO_IO_HANDLE_NONE;

66 status_t status = mpClientInterface->openOutput(outProfile->mModule->mHandle,

67 &output,

68 &config,

69 &outputDesc->mDevice,

70 String8(""),

71 &outputDesc->mLatency,

72 outputDesc->mFlags);

74 if (status != NO_ERROR) {

75 ALOGW("Cannot open output stream for device %08x on hw module %s",

76 outputDesc->mDevice,

77 mHwModules[i]->mName);

78 } else {

79 outputDesc->mSamplingRate = config.sample_rate;

80 outputDesc->mChannelMask = config.channel_mask;

81 outputDesc->mFormat = config.format;

83 for (size_t k = 0; k < outProfile->mSupportedDevices.size(); k++) {

84 audio_devices_t type = outProfile->mSupportedDevices[k]->mDeviceType;

85 ssize_t index =

86 mAvailableOutputDevices.indexOf(outProfile->mSupportedDevices[k]);

87 /*如果打开的输出设备有效，为它分配一个有效的ID，赋值对应的module*/

88 // give a valid ID to an attached device once confirmed it is reachable

89 if ((index >= 0) && (mAvailableOutputDevices[index]->mId == 0)) {

90 mAvailableOutputDevices[index]->mId = nextUniqueId();

91 mAvailableOutputDevices[index]->mModule = mHwModules[i];

92 }

93 }

94 if (mPrimaryOutput == 0 &&

95 outProfile->mFlags & AUDIO_OUTPUT_FLAG_PRIMARY) {

96 mPrimaryOutput = output;

97 }

98 addOutput(output, outputDesc);

99 setOutputDevice(output,

100 outputDesc->mDevice,

101 true);

102 }

103 }

104 // open input streams needed to access attached devices to validate

105 // mAvailableInputDevices list

106 for (size_t j = 0; j < mHwModules[i]->mInputProfiles.size(); j++)

107 {

108 const sp<IOProfile> inProfile = mHwModules[i]->mInputProfiles[j];

109

110 if (inProfile->mSupportedDevices.isEmpty()) {

111 ALOGW("Input profile contains no device on module %s", mHwModules[i]->mName);

112 continue;

113 }

114 // chose first device present in mSupportedDevices also part of

115 // inputDeviceTypes

116 audio_devices_t profileType = AUDIO_DEVICE_NONE;

117 for (size_t k = 0; k < inProfile->mSupportedDevices.size(); k++) {

118 profileType = inProfile->mSupportedDevices[k]->mDeviceType;

119 if (profileType & inputDeviceTypes) {

120 break;

121 }

122 }

123 if ((profileType & inputDeviceTypes) == 0) {

124 continue;

125 }

126 sp<AudioInputDescriptor> inputDesc = new AudioInputDescriptor(inProfile);

127

128 inputDesc->mInputSource = AUDIO_SOURCE_MIC;

129 inputDesc->mDevice = profileType;

130

131 // find the address

132 DeviceVector inputDevices = mAvailableInputDevices.getDevicesFromType(profileType);

133 // the inputs vector must be of size 1, but we don't want to crash here

134 String8 address = inputDevices.size() > 0 ? inputDevices.itemAt(0)->mAddress

135 : String8("");

136 ALOGV(" for input device 0x%x using address %s", profileType, address.string());

137 ALOGE_IF(inputDevices.size() == 0, "Input device list is empty!");

138

139 audio_config_t config = AUDIO_CONFIG_INITIALIZER;

140 config.sample_rate = inputDesc->mSamplingRate;

141 config.channel_mask = inputDesc->mChannelMask;

142 config.format = inputDesc->mFormat;

143 audio_io_handle_t input = AUDIO_IO_HANDLE_NONE;

144 status_t status = mpClientInterface->openInput(inProfile->mModule->mHandle,

145 &input,

146 &config,

147 &inputDesc->mDevice,

148 address,

149 AUDIO_SOURCE_MIC,

150 AUDIO_INPUT_FLAG_NONE);

151

152 if (status == NO_ERROR) {

153 for (size_t k = 0; k < inProfile->mSupportedDevices.size(); k++) {

154 audio_devices_t type = inProfile->mSupportedDevices[k]->mDeviceType;

155 ssize_t index =

156 mAvailableInputDevices.indexOf(inProfile->mSupportedDevices[k]);

157 // give a valid ID to an attached device once confirmed it is reachable

158 if ((index >= 0) && (mAvailableInputDevices[index]->mId == 0)) {

159 mAvailableInputDevices[index]->mId = nextUniqueId();

160 mAvailableInputDevices[index]->mModule = mHwModules[i];

161 }

162 }

163 mpClientInterface->closeInput(input);

164 } else {

165 ALOGW("Cannot open input stream for device %08x on hw module %s",

166 inputDesc->mDevice,

167 mHwModules[i]->mName);

168 }

169 }

170 }

171

172 /*确认mAvailableOutputDevices设备列表中的所有输出设备的id是有效的，如果无效，移除该设备*/

173 // make sure all attached devices have been allocated a unique ID

174 for (size_t i = 0; i < mAvailableOutputDevices.size();) {

175 if (mAvailableOutputDevices[i]->mId == 0) {

176 ALOGW("Input device %08x unreachable", mAvailableOutputDevices[i]->mDeviceType);

177 mAvailableOutputDevices.remove(mAvailableOutputDevices[i]);

178 continue;

179 }

180 i++;

181 }

182 for (size_t i = 0; i < mAvailableInputDevices.size();) {

183 if (mAvailableInputDevices[i]->mId == 0) {

184 ALOGW("Input device %08x unreachable", mAvailableInputDevices[i]->mDeviceType);

185 mAvailableInputDevices.remove(mAvailableInputDevices[i]);

186 continue;

187 }

188 i++;

189 }

190

191 /*确认默认输出设备是有效的*/

192 // make sure default device is reachable

193 if (mAvailableOutputDevices.indexOf(mDefaultOutputDevice) < 0) {

194 ALOGE("Default device %08x is unreachable", mDefaultOutputDevice->mDeviceType);

195 }

196

197 ALOGE_IF((mPrimaryOutput == 0), "Failed to open primary output");

198

199 /*更新下音频策略*/

200 updateDevicesAndOutputs();

201 }

在创建AudioPolicyManager的时候，会load audio_policy.conf文件建立起有效输出设备列表mAvailableOutputDevices 和有效输入设备列表mAvailableInputDevices。

1 status_t AudioPolicyManager::loadAudioPolicyConfig(const char *path)

2 {

3 cnode *root;

4 char *data;

6 data = (char *)load_file(path, NULL);

7 if (data == NULL) {

8 return -ENODEV;

9 }

10 root = config_node("", "");

11 config_load(root, data);

13 /*根据配置文件支持的module,分别load audio.<primary/a2dp/usb>.<device>.so 这三个so文件 */

14 loadHwModules(root);

15 // legacy audio_policy.conf files have one global_configuration section

16 /*加载audio_policy.conf 中的global_configuration 配置*/

17 loadGlobalConfig(root, getModuleFromName(AUDIO_HARDWARE_MODULE_ID_PRIMARY));

18 config_free(root);

19 free(root);

20 free(data);

22 ALOGI("loadAudioPolicyConfig() loaded %s\n", path);

23 }

配置文件中可以看到，一般平台都会支持primary, a2dp, usb三中输出方式，所以，这里会分别load三个module的so文件。如果两个地方配置文件找不到，也会创建一个默认的primary module来进行音频的输入输出。

为什么会想到看这个呢，是因为在播放的音乐的时候，选用播放模式的时候，会判断是否可以用compress_offload模式，其中，有一项判断，就是判断它的设置是否在compress_offload支持的范围，而compress_offload支持的参数，就是在此conf文件中配置的。

例如，它支持8k~48k之间的采样率，支持MP3，AAC格式，支持常见的喇叭，听筒，耳机等输出，如果设置的参数，不在此配置内，就不能使用compress_offload模式进行播放

1 compress_offload {

2 sampling_rates 8000|11025|16000|22050|32000|44100|48000

3 channel_masks AUDIO_CHANNEL_OUT_MONO|AUDIO_CHANNEL_OUT_STEREO

4 formats AUDIO_FORMAT_MP3|AUDIO_FORMAT_AAC_LC|AUDIO_FORMAT_AAC_HE_V1|AUDIO_FORMAT_AAC_HE_V2

6 flags AUDIO_OUTPUT_FLAG_DIRECT|AUDIO_OUTPUT_FLAG_COMPRESS_OFFLOAD|AUDIO_OUTPUT_FLAG_NON_BLOCKING

转载：https://www.cnblogs.com/wulizhi/p/8179067.html