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      1 /*
      2  * Copyright (C) 2008 The Android Open Source Project
      3  *
      4  * Licensed under the Apache License, Version 2.0 (the "License");
      5  * you may not use this file except in compliance with the License.
      6  * You may obtain a copy of the License at
      7  *
      8  *      http://www.apache.org/licenses/LICENSE-2.0
      9  *
     10  * Unless required by applicable law or agreed to in writing, software
     11  * distributed under the License is distributed on an "AS IS" BASIS,
     12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
     13  * See the License for the specific language governing permissions and
     14  * limitations under the License.
     15  */
     16 
     17 #ifndef ANDROID_AUDIOSYSTEM_H_
     18 #define ANDROID_AUDIOSYSTEM_H_
     19 
     20 #include <utils/RefBase.h>
     21 #include <utils/threads.h>
     22 #include <media/IAudioFlinger.h>
     23 
     24 namespace android {
     25 
     26 typedef void (*audio_error_callback)(status_t err);
     27 typedef int audio_io_handle_t;
     28 
     29 class IAudioPolicyService;
     30 class String8;
     31 
     32 class AudioSystem
     33 {
     34 public:
     35 
     36     enum stream_type {
     37         DEFAULT          =-1,
     38         VOICE_CALL       = 0,
     39         SYSTEM           = 1,
     40         RING             = 2,
     41         MUSIC            = 3,
     42         ALARM            = 4,
     43         NOTIFICATION     = 5,
     44         BLUETOOTH_SCO    = 6,
     45         ENFORCED_AUDIBLE = 7, // Sounds that cannot be muted by user and must be routed to speaker
     46         DTMF             = 8,
     47         TTS              = 9,
     48         NUM_STREAM_TYPES
     49     };
     50 
     51     // Audio sub formats (see AudioSystem::audio_format).
     52     enum pcm_sub_format {
     53         PCM_SUB_16_BIT          = 0x1, // must be 1 for backward compatibility
     54         PCM_SUB_8_BIT           = 0x2, // must be 2 for backward compatibility
     55     };
     56 
     57     // MP3 sub format field definition : can use 11 LSBs in the same way as MP3 frame header to specify
     58     // bit rate, stereo mode, version...
     59     enum mp3_sub_format {
     60         //TODO
     61     };
     62 
     63     // AMR NB/WB sub format field definition: specify frame block interleaving, bandwidth efficient or octet aligned,
     64     // encoding mode for recording...
     65     enum amr_sub_format {
     66         //TODO
     67     };
     68 
     69     // AAC sub format field definition: specify profile or bitrate for recording...
     70     enum aac_sub_format {
     71         //TODO
     72     };
     73 
     74     // VORBIS sub format field definition: specify quality for recording...
     75     enum vorbis_sub_format {
     76         //TODO
     77     };
     78 
     79     // Audio format consists in a main format field (upper 8 bits) and a sub format field (lower 24 bits).
     80     // The main format indicates the main codec type. The sub format field indicates options and parameters
     81     // for each format. The sub format is mainly used for record to indicate for instance the requested bitrate
     82     // or profile. It can also be used for certain formats to give informations not present in the encoded
     83     // audio stream (e.g. octet alignement for AMR).
     84     enum audio_format {
     85         INVALID_FORMAT      = -1,
     86         FORMAT_DEFAULT      = 0,
     87         PCM                 = 0x00000000, // must be 0 for backward compatibility
     88         MP3                 = 0x01000000,
     89         AMR_NB              = 0x02000000,
     90         AMR_WB              = 0x03000000,
     91         AAC                 = 0x04000000,
     92         HE_AAC_V1           = 0x05000000,
     93         HE_AAC_V2           = 0x06000000,
     94         VORBIS              = 0x07000000,
     95         MAIN_FORMAT_MASK    = 0xFF000000,
     96         SUB_FORMAT_MASK     = 0x00FFFFFF,
     97         // Aliases
     98         PCM_16_BIT          = (PCM|PCM_SUB_16_BIT),
     99         PCM_8_BIT          = (PCM|PCM_SUB_8_BIT)
    100     };
    101 
    102 
    103     // Channel mask definitions must be kept in sync with JAVA values in /media/java/android/media/AudioFormat.java
    104     enum audio_channels {
    105         // output channels
    106         CHANNEL_OUT_FRONT_LEFT = 0x4,
    107         CHANNEL_OUT_FRONT_RIGHT = 0x8,
    108         CHANNEL_OUT_FRONT_CENTER = 0x10,
    109         CHANNEL_OUT_LOW_FREQUENCY = 0x20,
    110         CHANNEL_OUT_BACK_LEFT = 0x40,
    111         CHANNEL_OUT_BACK_RIGHT = 0x80,
    112         CHANNEL_OUT_FRONT_LEFT_OF_CENTER = 0x100,
    113         CHANNEL_OUT_FRONT_RIGHT_OF_CENTER = 0x200,
    114         CHANNEL_OUT_BACK_CENTER = 0x400,
    115         CHANNEL_OUT_MONO = CHANNEL_OUT_FRONT_LEFT,
    116         CHANNEL_OUT_STEREO = (CHANNEL_OUT_FRONT_LEFT | CHANNEL_OUT_FRONT_RIGHT),
    117         CHANNEL_OUT_QUAD = (CHANNEL_OUT_FRONT_LEFT | CHANNEL_OUT_FRONT_RIGHT |
    118                 CHANNEL_OUT_BACK_LEFT | CHANNEL_OUT_BACK_RIGHT),
    119         CHANNEL_OUT_SURROUND = (CHANNEL_OUT_FRONT_LEFT | CHANNEL_OUT_FRONT_RIGHT |
    120                 CHANNEL_OUT_FRONT_CENTER | CHANNEL_OUT_BACK_CENTER),
    121         CHANNEL_OUT_5POINT1 = (CHANNEL_OUT_FRONT_LEFT | CHANNEL_OUT_FRONT_RIGHT |
    122                 CHANNEL_OUT_FRONT_CENTER | CHANNEL_OUT_LOW_FREQUENCY | CHANNEL_OUT_BACK_LEFT | CHANNEL_OUT_BACK_RIGHT),
    123         CHANNEL_OUT_7POINT1 = (CHANNEL_OUT_FRONT_LEFT | CHANNEL_OUT_FRONT_RIGHT |
    124                 CHANNEL_OUT_FRONT_CENTER | CHANNEL_OUT_LOW_FREQUENCY | CHANNEL_OUT_BACK_LEFT | CHANNEL_OUT_BACK_RIGHT |
    125                 CHANNEL_OUT_FRONT_LEFT_OF_CENTER | CHANNEL_OUT_FRONT_RIGHT_OF_CENTER),
    126         CHANNEL_OUT_ALL = (CHANNEL_OUT_FRONT_LEFT | CHANNEL_OUT_FRONT_RIGHT |
    127                 CHANNEL_OUT_FRONT_CENTER | CHANNEL_OUT_LOW_FREQUENCY | CHANNEL_OUT_BACK_LEFT | CHANNEL_OUT_BACK_RIGHT |
    128                 CHANNEL_OUT_FRONT_LEFT_OF_CENTER | CHANNEL_OUT_FRONT_RIGHT_OF_CENTER | CHANNEL_OUT_BACK_CENTER),
    129 
    130         // input channels
    131         CHANNEL_IN_LEFT = 0x4,
    132         CHANNEL_IN_RIGHT = 0x8,
    133         CHANNEL_IN_FRONT = 0x10,
    134         CHANNEL_IN_BACK = 0x20,
    135         CHANNEL_IN_LEFT_PROCESSED = 0x40,
    136         CHANNEL_IN_RIGHT_PROCESSED = 0x80,
    137         CHANNEL_IN_FRONT_PROCESSED = 0x100,
    138         CHANNEL_IN_BACK_PROCESSED = 0x200,
    139         CHANNEL_IN_PRESSURE = 0x400,
    140         CHANNEL_IN_X_AXIS = 0x800,
    141         CHANNEL_IN_Y_AXIS = 0x1000,
    142         CHANNEL_IN_Z_AXIS = 0x2000,
    143         CHANNEL_IN_VOICE_UPLINK = 0x4000,
    144         CHANNEL_IN_VOICE_DNLINK = 0x8000,
    145         CHANNEL_IN_MONO = CHANNEL_IN_FRONT,
    146         CHANNEL_IN_STEREO = (CHANNEL_IN_LEFT | CHANNEL_IN_RIGHT),
    147         CHANNEL_IN_ALL = (CHANNEL_IN_LEFT | CHANNEL_IN_RIGHT | CHANNEL_IN_FRONT | CHANNEL_IN_BACK|
    148                 CHANNEL_IN_LEFT_PROCESSED | CHANNEL_IN_RIGHT_PROCESSED | CHANNEL_IN_FRONT_PROCESSED | CHANNEL_IN_BACK_PROCESSED|
    149                 CHANNEL_IN_PRESSURE | CHANNEL_IN_X_AXIS | CHANNEL_IN_Y_AXIS | CHANNEL_IN_Z_AXIS |
    150                 CHANNEL_IN_VOICE_UPLINK | CHANNEL_IN_VOICE_DNLINK)
    151     };
    152 
    153     enum audio_mode {
    154         MODE_INVALID = -2,
    155         MODE_CURRENT = -1,
    156         MODE_NORMAL = 0,
    157         MODE_RINGTONE,
    158         MODE_IN_CALL,
    159         MODE_IN_COMMUNICATION,
    160         NUM_MODES  // not a valid entry, denotes end-of-list
    161     };
    162 
    163     enum audio_in_acoustics {
    164         AGC_ENABLE    = 0x0001,
    165         AGC_DISABLE   = 0,
    166         NS_ENABLE     = 0x0002,
    167         NS_DISABLE    = 0,
    168         TX_IIR_ENABLE = 0x0004,
    169         TX_DISABLE    = 0
    170     };
    171 
    172     // special audio session values
    173     enum audio_sessions {
    174         SESSION_OUTPUT_STAGE = -1, // session for effects attached to a particular output stream
    175                                    // (value must be less than 0)
    176         SESSION_OUTPUT_MIX = 0,    // session for effects applied to output mix. These effects can
    177                                    // be moved by audio policy manager to another output stream
    178                                    // (value must be 0)
    179     };
    180 
    181     /* These are static methods to control the system-wide AudioFlinger
    182      * only privileged processes can have access to them
    183      */
    184 
    185     // mute/unmute microphone
    186     static status_t muteMicrophone(bool state);
    187     static status_t isMicrophoneMuted(bool *state);
    188 
    189     // set/get master volume
    190     static status_t setMasterVolume(float value);
    191     static status_t getMasterVolume(float* volume);
    192     // mute/unmute audio outputs
    193     static status_t setMasterMute(bool mute);
    194     static status_t getMasterMute(bool* mute);
    195 
    196     // set/get stream volume on specified output
    197     static status_t setStreamVolume(int stream, float value, int output);
    198     static status_t getStreamVolume(int stream, float* volume, int output);
    199 
    200     // mute/unmute stream
    201     static status_t setStreamMute(int stream, bool mute);
    202     static status_t getStreamMute(int stream, bool* mute);
    203 
    204     // set audio mode in audio hardware (see AudioSystem::audio_mode)
    205     static status_t setMode(int mode);
    206 
    207     // returns true in *state if tracks are active on the specified stream
    208     static status_t isStreamActive(int stream, bool *state);
    209 
    210     // set/get audio hardware parameters. The function accepts a list of parameters
    211     // key value pairs in the form: key1=value1;key2=value2;...
    212     // Some keys are reserved for standard parameters (See AudioParameter class).
    213     static status_t setParameters(audio_io_handle_t ioHandle, const String8& keyValuePairs);
    214     static String8  getParameters(audio_io_handle_t ioHandle, const String8& keys);
    215 
    216     static void setErrorCallback(audio_error_callback cb);
    217 
    218     // helper function to obtain AudioFlinger service handle
    219     static const sp<IAudioFlinger>& get_audio_flinger();
    220 
    221     static float linearToLog(int volume);
    222     static int logToLinear(float volume);
    223 
    224     static status_t getOutputSamplingRate(int* samplingRate, int stream = DEFAULT);
    225     static status_t getOutputFrameCount(int* frameCount, int stream = DEFAULT);
    226     static status_t getOutputLatency(uint32_t* latency, int stream = DEFAULT);
    227 
    228     static bool routedToA2dpOutput(int streamType);
    229 
    230     static status_t getInputBufferSize(uint32_t sampleRate, int format, int channelCount,
    231         size_t* buffSize);
    232 
    233     static status_t setVoiceVolume(float volume);
    234 
    235     // return the number of audio frames written by AudioFlinger to audio HAL and
    236     // audio dsp to DAC since the output on which the specificed stream is playing
    237     // has exited standby.
    238     // returned status (from utils/Errors.h) can be:
    239     // - NO_ERROR: successful operation, halFrames and dspFrames point to valid data
    240     // - INVALID_OPERATION: Not supported on current hardware platform
    241     // - BAD_VALUE: invalid parameter
    242     // NOTE: this feature is not supported on all hardware platforms and it is
    243     // necessary to check returned status before using the returned values.
    244     static status_t getRenderPosition(uint32_t *halFrames, uint32_t *dspFrames, int stream = DEFAULT);
    245 
    246     static unsigned int  getInputFramesLost(audio_io_handle_t ioHandle);
    247 
    248     static int newAudioSessionId();
    249     //
    250     // AudioPolicyService interface
    251     //
    252 
    253     enum audio_devices {
    254         // output devices
    255         DEVICE_OUT_EARPIECE = 0x1,
    256         DEVICE_OUT_SPEAKER = 0x2,
    257         DEVICE_OUT_WIRED_HEADSET = 0x4,
    258         DEVICE_OUT_WIRED_HEADPHONE = 0x8,
    259         DEVICE_OUT_BLUETOOTH_SCO = 0x10,
    260         DEVICE_OUT_BLUETOOTH_SCO_HEADSET = 0x20,
    261         DEVICE_OUT_BLUETOOTH_SCO_CARKIT = 0x40,
    262         DEVICE_OUT_BLUETOOTH_A2DP = 0x80,
    263         DEVICE_OUT_BLUETOOTH_A2DP_HEADPHONES = 0x100,
    264         DEVICE_OUT_BLUETOOTH_A2DP_SPEAKER = 0x200,
    265         DEVICE_OUT_AUX_DIGITAL = 0x400,
    266         DEVICE_OUT_DEFAULT = 0x8000,
    267         DEVICE_OUT_ALL = (DEVICE_OUT_EARPIECE | DEVICE_OUT_SPEAKER | DEVICE_OUT_WIRED_HEADSET |
    268                 DEVICE_OUT_WIRED_HEADPHONE | DEVICE_OUT_BLUETOOTH_SCO | DEVICE_OUT_BLUETOOTH_SCO_HEADSET |
    269                 DEVICE_OUT_BLUETOOTH_SCO_CARKIT | DEVICE_OUT_BLUETOOTH_A2DP | DEVICE_OUT_BLUETOOTH_A2DP_HEADPHONES |
    270                 DEVICE_OUT_BLUETOOTH_A2DP_SPEAKER | DEVICE_OUT_AUX_DIGITAL | DEVICE_OUT_DEFAULT),
    271         DEVICE_OUT_ALL_A2DP = (DEVICE_OUT_BLUETOOTH_A2DP | DEVICE_OUT_BLUETOOTH_A2DP_HEADPHONES |
    272                 DEVICE_OUT_BLUETOOTH_A2DP_SPEAKER),
    273 
    274         // input devices
    275         DEVICE_IN_COMMUNICATION = 0x10000,
    276         DEVICE_IN_AMBIENT = 0x20000,
    277         DEVICE_IN_BUILTIN_MIC = 0x40000,
    278         DEVICE_IN_BLUETOOTH_SCO_HEADSET = 0x80000,
    279         DEVICE_IN_WIRED_HEADSET = 0x100000,
    280         DEVICE_IN_AUX_DIGITAL = 0x200000,
    281         DEVICE_IN_VOICE_CALL = 0x400000,
    282         DEVICE_IN_BACK_MIC = 0x800000,
    283         DEVICE_IN_DEFAULT = 0x80000000,
    284 
    285         DEVICE_IN_ALL = (DEVICE_IN_COMMUNICATION | DEVICE_IN_AMBIENT | DEVICE_IN_BUILTIN_MIC |
    286                 DEVICE_IN_BLUETOOTH_SCO_HEADSET | DEVICE_IN_WIRED_HEADSET | DEVICE_IN_AUX_DIGITAL |
    287                 DEVICE_IN_VOICE_CALL | DEVICE_IN_BACK_MIC | DEVICE_IN_DEFAULT)
    288     };
    289 
    290     // device connection states used for setDeviceConnectionState()
    291     enum device_connection_state {
    292         DEVICE_STATE_UNAVAILABLE,
    293         DEVICE_STATE_AVAILABLE,
    294         NUM_DEVICE_STATES
    295     };
    296 
    297     // request to open a direct output with getOutput() (by opposition to sharing an output with other AudioTracks)
    298     enum output_flags {
    299         OUTPUT_FLAG_INDIRECT = 0x0,
    300         OUTPUT_FLAG_DIRECT = 0x1
    301     };
    302 
    303     // device categories used for setForceUse()
    304     enum forced_config {
    305         FORCE_NONE,
    306         FORCE_SPEAKER,
    307         FORCE_HEADPHONES,
    308         FORCE_BT_SCO,
    309         FORCE_BT_A2DP,
    310         FORCE_WIRED_ACCESSORY,
    311         FORCE_BT_CAR_DOCK,
    312         FORCE_BT_DESK_DOCK,
    313         NUM_FORCE_CONFIG,
    314         FORCE_DEFAULT = FORCE_NONE
    315     };
    316 
    317     // usages used for setForceUse()
    318     enum force_use {
    319         FOR_COMMUNICATION,
    320         FOR_MEDIA,
    321         FOR_RECORD,
    322         FOR_DOCK,
    323         NUM_FORCE_USE
    324     };
    325 
    326     // types of io configuration change events received with ioConfigChanged()
    327     enum io_config_event {
    328         OUTPUT_OPENED,
    329         OUTPUT_CLOSED,
    330         OUTPUT_CONFIG_CHANGED,
    331         INPUT_OPENED,
    332         INPUT_CLOSED,
    333         INPUT_CONFIG_CHANGED,
    334         STREAM_CONFIG_CHANGED,
    335         NUM_CONFIG_EVENTS
    336     };
    337 
    338     // audio output descritor used to cache output configurations in client process to avoid frequent calls
    339     // through IAudioFlinger
    340     class OutputDescriptor {
    341     public:
    342         OutputDescriptor()
    343         : samplingRate(0), format(0), channels(0), frameCount(0), latency(0)  {}
    344 
    345         uint32_t samplingRate;
    346         int32_t format;
    347         int32_t channels;
    348         size_t frameCount;
    349         uint32_t latency;
    350     };
    351 
    352     //
    353     // IAudioPolicyService interface (see AudioPolicyInterface for method descriptions)
    354     //
    355     static status_t setDeviceConnectionState(audio_devices device, device_connection_state state, const char *device_address);
    356     static device_connection_state getDeviceConnectionState(audio_devices device, const char *device_address);
    357     static status_t setPhoneState(int state);
    358     static status_t setRingerMode(uint32_t mode, uint32_t mask);
    359     static status_t setForceUse(force_use usage, forced_config config);
    360     static forced_config getForceUse(force_use usage);
    361     static audio_io_handle_t getOutput(stream_type stream,
    362                                         uint32_t samplingRate = 0,
    363                                         uint32_t format = FORMAT_DEFAULT,
    364                                         uint32_t channels = CHANNEL_OUT_STEREO,
    365                                         output_flags flags = OUTPUT_FLAG_INDIRECT);
    366     static status_t startOutput(audio_io_handle_t output,
    367                                 AudioSystem::stream_type stream,
    368                                 int session = 0);
    369     static status_t stopOutput(audio_io_handle_t output,
    370                                AudioSystem::stream_type stream,
    371                                int session = 0);
    372     static void releaseOutput(audio_io_handle_t output);
    373     static audio_io_handle_t getInput(int inputSource,
    374                                     uint32_t samplingRate = 0,
    375                                     uint32_t format = FORMAT_DEFAULT,
    376                                     uint32_t channels = CHANNEL_IN_MONO,
    377                                     audio_in_acoustics acoustics = (audio_in_acoustics)0);
    378     static status_t startInput(audio_io_handle_t input);
    379     static status_t stopInput(audio_io_handle_t input);
    380     static void releaseInput(audio_io_handle_t input);
    381     static status_t initStreamVolume(stream_type stream,
    382                                       int indexMin,
    383                                       int indexMax);
    384     static status_t setStreamVolumeIndex(stream_type stream, int index);
    385     static status_t getStreamVolumeIndex(stream_type stream, int *index);
    386 
    387     static uint32_t getStrategyForStream(stream_type stream);
    388 
    389     static audio_io_handle_t getOutputForEffect(effect_descriptor_t *desc);
    390     static status_t registerEffect(effect_descriptor_t *desc,
    391                                     audio_io_handle_t output,
    392                                     uint32_t strategy,
    393                                     int session,
    394                                     int id);
    395     static status_t unregisterEffect(int id);
    396 
    397     static const sp<IAudioPolicyService>& get_audio_policy_service();
    398 
    399     // ----------------------------------------------------------------------------
    400 
    401     static uint32_t popCount(uint32_t u);
    402     static bool isOutputDevice(audio_devices device);
    403     static bool isInputDevice(audio_devices device);
    404     static bool isA2dpDevice(audio_devices device);
    405     static bool isBluetoothScoDevice(audio_devices device);
    406     static bool isLowVisibility(stream_type stream);
    407     static bool isOutputChannel(uint32_t channel);
    408     static bool isInputChannel(uint32_t channel);
    409     static bool isValidFormat(uint32_t format);
    410     static bool isLinearPCM(uint32_t format);
    411 
    412 private:
    413 
    414     class AudioFlingerClient: public IBinder::DeathRecipient, public BnAudioFlingerClient
    415     {
    416     public:
    417         AudioFlingerClient() {
    418         }
    419 
    420         // DeathRecipient
    421         virtual void binderDied(const wp<IBinder>& who);
    422 
    423         // IAudioFlingerClient
    424 
    425         // indicate a change in the configuration of an output or input: keeps the cached
    426         // values for output/input parameters upto date in client process
    427         virtual void ioConfigChanged(int event, int ioHandle, void *param2);
    428     };
    429 
    430     class AudioPolicyServiceClient: public IBinder::DeathRecipient
    431     {
    432     public:
    433         AudioPolicyServiceClient() {
    434         }
    435 
    436         // DeathRecipient
    437         virtual void binderDied(const wp<IBinder>& who);
    438     };
    439 
    440     static sp<AudioFlingerClient> gAudioFlingerClient;
    441     static sp<AudioPolicyServiceClient> gAudioPolicyServiceClient;
    442     friend class AudioFlingerClient;
    443     friend class AudioPolicyServiceClient;
    444 
    445     static Mutex gLock;
    446     static sp<IAudioFlinger> gAudioFlinger;
    447     static audio_error_callback gAudioErrorCallback;
    448 
    449     static size_t gInBuffSize;
    450     // previous parameters for recording buffer size queries
    451     static uint32_t gPrevInSamplingRate;
    452     static int gPrevInFormat;
    453     static int gPrevInChannelCount;
    454 
    455     static sp<IAudioPolicyService> gAudioPolicyService;
    456 
    457     // mapping between stream types and outputs
    458     static DefaultKeyedVector<int, audio_io_handle_t> gStreamOutputMap;
    459     // list of output descritor containing cached parameters (sampling rate, framecount, channel count...)
    460     static DefaultKeyedVector<audio_io_handle_t, OutputDescriptor *> gOutputs;
    461 };
    462 
    463 class AudioParameter {
    464 
    465 public:
    466     AudioParameter() {}
    467     AudioParameter(const String8& keyValuePairs);
    468     virtual ~AudioParameter();
    469 
    470     // reserved parameter keys for changing standard parameters with setParameters() function.
    471     // Using these keys is mandatory for AudioFlinger to properly monitor audio output/input
    472     // configuration changes and act accordingly.
    473     //  keyRouting: to change audio routing, value is an int in AudioSystem::audio_devices
    474     //  keySamplingRate: to change sampling rate routing, value is an int
    475     //  keyFormat: to change audio format, value is an int in AudioSystem::audio_format
    476     //  keyChannels: to change audio channel configuration, value is an int in AudioSystem::audio_channels
    477     //  keyFrameCount: to change audio output frame count, value is an int
    478     //  keyInputSource: to change audio input source, value is an int in audio_source
    479     //     (defined in media/mediarecorder.h)
    480     static const char *keyRouting;
    481     static const char *keySamplingRate;
    482     static const char *keyFormat;
    483     static const char *keyChannels;
    484     static const char *keyFrameCount;
    485     static const char *keyInputSource;
    486 
    487     String8 toString();
    488 
    489     status_t add(const String8& key, const String8& value);
    490     status_t addInt(const String8& key, const int value);
    491     status_t addFloat(const String8& key, const float value);
    492 
    493     status_t remove(const String8& key);
    494 
    495     status_t get(const String8& key, String8& value);
    496     status_t getInt(const String8& key, int& value);
    497     status_t getFloat(const String8& key, float& value);
    498     status_t getAt(size_t index, String8& key, String8& value);
    499 
    500     size_t size() { return mParameters.size(); }
    501 
    502 private:
    503     String8 mKeyValuePairs;
    504     KeyedVector <String8, String8> mParameters;
    505 };
    506 
    507 };  // namespace android
    508 
    509 #endif  /*ANDROID_AUDIOSYSTEM_H_*/
    510