AudioHardwareInterface.h

Go to the documentation of this file.

/*
 * Copyright (C) 2007 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

#ifndef ANDROID_AUDIO_HARDWARE_INTERFACE_H
#define ANDROID_AUDIO_HARDWARE_INTERFACE_H

#include <stdint.h>
#include <sys/types.h>

#include <utils/Errors.h>
#include <utils/Vector.h>
#include <utils/String16.h>

#include <media/IAudioFlinger.h>
#include "media/AudioSystem.h"


namespace android {

// ----------------------------------------------------------------------------

/**
 * AudioStreamOut is the abstraction interface for the audio output hardware.
 *
 * It provides information about various properties of the audio output hardware driver.
 */
class AudioStreamOut {
public:
    virtual             ~AudioStreamOut() = 0;

    /** return audio sampling rate in hz - eg. 44100 */
    virtual uint32_t    sampleRate() const = 0;

    /** returns size of output buffer - eg. 4800 */
    virtual size_t      bufferSize() const = 0;

    /**
     * return number of output audio channels.
     * Acceptable values are 1 (mono) or 2 (stereo)
     */
    virtual int         channelCount() const = 0;

    /**
     * return audio format in 8bit or 16bit PCM format -
     * eg. AudioSystem:PCM_16_BIT
     */
    virtual int         format() const = 0;

    /**
     * return the frame size (number of bytes per sample).
     */
    uint32_t    frameSize() const { return channelCount()*((format()==AudioSystem::PCM_16_BIT)?sizeof(int16_t):sizeof(int8_t)); }

    /**
     * return the audio hardware driver latency in milli seconds.
     */
    virtual uint32_t    latency() const = 0;

    /**
     * Use this method in situations where audio mixing is done in the
     * hardware. This method serves as a direct interface with hardware,
     * allowing you to directly set the volume as apposed to via the framework.
     * This method might produce multiple PCM outputs or hardware accelerated
     * codecs, such as MP3 or AAC.
     */
    virtual status_t    setVolume(float volume) = 0;

    /** write audio buffer to driver. Returns number of bytes written */
    virtual ssize_t     write(const void* buffer, size_t bytes) = 0;

    /**
     * Put the audio hardware output into standby mode. Returns
     * status based on include/utils/Errors.h
     */
    virtual status_t    standby() = 0;

    /** dump the state of the audio output device */
    virtual status_t dump(int fd, const Vector<String16>& args) = 0;
};

/**
 * AudioStreamIn is the abstraction interface for the audio input hardware.
 *
 * It defines the various properties of the audio hardware input driver.
 */
class AudioStreamIn {
public:
    virtual             ~AudioStreamIn() = 0;

    /** return the input buffer size allowed by audio driver */
    virtual size_t      bufferSize() const = 0;

    /** return the number of audio input channels */
    virtual int         channelCount() const = 0;

    /**
     * return audio format in 8bit or 16bit PCM format -
     * eg. AudioSystem:PCM_16_BIT
     */
    virtual int         format() const = 0;

    /**
     * return the frame size (number of bytes per sample).
     */
    uint32_t    frameSize() const { return channelCount()*((format()==AudioSystem::PCM_16_BIT)?sizeof(int16_t):sizeof(int8_t)); }

    /** set the input gain for the audio driver. This method is for
     *  for future use */
    virtual status_t    setGain(float gain) = 0;

    /** read audio buffer in from audio driver */
    virtual ssize_t     read(void* buffer, ssize_t bytes) = 0;

    /** dump the state of the audio input device */
    virtual status_t dump(int fd, const Vector<String16>& args) = 0;

    /**
     * Put the audio hardware input into standby mode. Returns
     * status based on include/utils/Errors.h
     */
    virtual status_t    standby() = 0;

};

/**
 * AudioHardwareInterface.h defines the interface to the audio hardware abstraction layer.
 *
 * The interface supports setting and getting parameters, selecting audio routing
 * paths, and defining input and output streams.
 *
 * AudioFlinger initializes the audio hardware and immediately opens an output stream.
 * You can set Audio routing to output to handset, speaker, Bluetooth, or a headset.
 *
 * The audio input stream is initialized when AudioFlinger is called to carry out
 * a record operation.
 */
class AudioHardwareInterface
{
public:
    virtual ~AudioHardwareInterface() {}

    /**
     * check to see if the audio hardware interface has been initialized.
     * return status based on values defined in include/utils/Errors.h
     */
    virtual status_t    initCheck() = 0;

    /** set the audio volume of a voice call. Range is between 0.0 and 1.0 */
    virtual status_t    setVoiceVolume(float volume) = 0;

    /**
     * set the audio volume for all audio activities other than voice call.
     * Range between 0.0 and 1.0. If any value other than NO_ERROR is returned,
     * the software mixer will emulate this capability.
     */
    virtual status_t    setMasterVolume(float volume) = 0;

    /**
     * Audio routing methods. Routes defined in include/hardware_legacy/AudioSystem.h.
     * Audio routes can be (ROUTE_EARPIECE | ROUTE_SPEAKER | ROUTE_BLUETOOTH
     *                    | ROUTE_HEADSET)
     *
     * setRouting sets the routes for a mode. This is called at startup. It is
     * also called when a new device is connected, such as a wired headset is
     * plugged in or a Bluetooth headset is paired.
     */
    virtual status_t    setRouting(int mode, uint32_t routes) = 0;

    virtual status_t    getRouting(int mode, uint32_t* routes) = 0;

    /**
     * setMode is called when the audio mode changes. NORMAL mode is for
     * standard audio playback, RINGTONE when a ringtone is playing, and IN_CALL
     * when a call is in progress.
     */
    virtual status_t    setMode(int mode) = 0;
    virtual status_t    getMode(int* mode) = 0;

    // mic mute
    virtual status_t    setMicMute(bool state) = 0;
    virtual status_t    getMicMute(bool* state) = 0;

    // Temporary interface, do not use
    // TODO: Replace with a more generic key:value get/set mechanism
    virtual status_t    setParameter(const char* key, const char* value) = 0;

    // Returns audio input buffer size according to parameters passed or 0 if one of the
    // parameters is not supported
    virtual size_t    getInputBufferSize(uint32_t sampleRate, int format, int channelCount) = 0;
    
    /** This method creates and opens the audio hardware output stream */
    virtual AudioStreamOut* openOutputStream(
                                int format=0,
                                int channelCount=0,
                                uint32_t sampleRate=0,
                                status_t *status=0) = 0;

    /** This method creates and opens the audio hardware input stream */
    virtual AudioStreamIn* openInputStream(
                                int inputSource,
                                int format,
                                int channelCount,
                                uint32_t sampleRate,
                                status_t *status,
                                AudioSystem::audio_in_acoustics acoustics) = 0;

    /**This method dumps the state of the audio hardware */
    virtual status_t dumpState(int fd, const Vector<String16>& args) = 0;

    static AudioHardwareInterface* create();

protected:
    /**
     * doRouting actually initiates the routing. A call to setRouting
     * or setMode may result in a routing change. The generic logic calls
     * doRouting when required. If the device has any special requirements these
     * methods can be overriden.
     */
    virtual status_t    doRouting() = 0;

    virtual status_t dump(int fd, const Vector<String16>& args) = 0;
};

// ----------------------------------------------------------------------------

extern "C" AudioHardwareInterface* createAudioHardware(void);

}; // namespace android

#endif // ANDROID_AUDIO_HARDWARE_INTERFACE_H