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      1 /*
      2  * Copyright (C) 2007 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_AUDIOTRACK_H
     18 #define ANDROID_AUDIOTRACK_H
     19 
     20 #include <cutils/sched_policy.h>
     21 #include <media/AudioSystem.h>
     22 #include <media/AudioTimestamp.h>
     23 #include <media/IAudioTrack.h>
     24 #include <utils/threads.h>
     25 
     26 namespace android {
     27 
     28 // ----------------------------------------------------------------------------
     29 
     30 class audio_track_cblk_t;
     31 class AudioTrackClientProxy;
     32 class StaticAudioTrackClientProxy;
     33 
     34 // ----------------------------------------------------------------------------
     35 
     36 class AudioTrack : public RefBase
     37 {
     38 public:
     39     enum channel_index {
     40         MONO   = 0,
     41         LEFT   = 0,
     42         RIGHT  = 1
     43     };
     44 
     45     /* Events used by AudioTrack callback function (callback_t).
     46      * Keep in sync with frameworks/base/media/java/android/media/AudioTrack.java NATIVE_EVENT_*.
     47      */
     48     enum event_type {
     49         EVENT_MORE_DATA = 0,        // Request to write more data to buffer.
     50                                     // If this event is delivered but the callback handler
     51                                     // does not want to write more data, the handler must explicitly
     52                                     // ignore the event by setting frameCount to zero.
     53         EVENT_UNDERRUN = 1,         // Buffer underrun occurred.
     54         EVENT_LOOP_END = 2,         // Sample loop end was reached; playback restarted from
     55                                     // loop start if loop count was not 0.
     56         EVENT_MARKER = 3,           // Playback head is at the specified marker position
     57                                     // (See setMarkerPosition()).
     58         EVENT_NEW_POS = 4,          // Playback head is at a new position
     59                                     // (See setPositionUpdatePeriod()).
     60         EVENT_BUFFER_END = 5,       // Playback head is at the end of the buffer.
     61                                     // Not currently used by android.media.AudioTrack.
     62         EVENT_NEW_IAUDIOTRACK = 6,  // IAudioTrack was re-created, either due to re-routing and
     63                                     // voluntary invalidation by mediaserver, or mediaserver crash.
     64         EVENT_STREAM_END = 7,       // Sent after all the buffers queued in AF and HW are played
     65                                     // back (after stop is called)
     66         EVENT_NEW_TIMESTAMP = 8,    // Delivered periodically and when there's a significant change
     67                                     // in the mapping from frame position to presentation time.
     68                                     // See AudioTimestamp for the information included with event.
     69     };
     70 
     71     /* Client should declare Buffer on the stack and pass address to obtainBuffer()
     72      * and releaseBuffer().  See also callback_t for EVENT_MORE_DATA.
     73      */
     74 
     75     class Buffer
     76     {
     77     public:
     78         // FIXME use m prefix
     79         size_t      frameCount;   // number of sample frames corresponding to size;
     80                                   // on input it is the number of frames desired,
     81                                   // on output is the number of frames actually filled
     82                                   // (currently ignored, but will make the primary field in future)
     83 
     84         size_t      size;         // input/output in bytes == frameCount * frameSize
     85                                   // on output is the number of bytes actually filled
     86                                   // FIXME this is redundant with respect to frameCount,
     87                                   // and TRANSFER_OBTAIN mode is broken for 8-bit data
     88                                   // since we don't define the frame format
     89 
     90         union {
     91             void*       raw;
     92             short*      i16;      // signed 16-bit
     93             int8_t*     i8;       // unsigned 8-bit, offset by 0x80
     94         };
     95     };
     96 
     97     /* As a convenience, if a callback is supplied, a handler thread
     98      * is automatically created with the appropriate priority. This thread
     99      * invokes the callback when a new buffer becomes available or various conditions occur.
    100      * Parameters:
    101      *
    102      * event:   type of event notified (see enum AudioTrack::event_type).
    103      * user:    Pointer to context for use by the callback receiver.
    104      * info:    Pointer to optional parameter according to event type:
    105      *          - EVENT_MORE_DATA: pointer to AudioTrack::Buffer struct. The callback must not write
    106      *            more bytes than indicated by 'size' field and update 'size' if fewer bytes are
    107      *            written.
    108      *          - EVENT_UNDERRUN: unused.
    109      *          - EVENT_LOOP_END: pointer to an int indicating the number of loops remaining.
    110      *          - EVENT_MARKER: pointer to const uint32_t containing the marker position in frames.
    111      *          - EVENT_NEW_POS: pointer to const uint32_t containing the new position in frames.
    112      *          - EVENT_BUFFER_END: unused.
    113      *          - EVENT_NEW_IAUDIOTRACK: unused.
    114      *          - EVENT_STREAM_END: unused.
    115      *          - EVENT_NEW_TIMESTAMP: pointer to const AudioTimestamp.
    116      */
    117 
    118     typedef void (*callback_t)(int event, void* user, void *info);
    119 
    120     /* Returns the minimum frame count required for the successful creation of
    121      * an AudioTrack object.
    122      * Returned status (from utils/Errors.h) can be:
    123      *  - NO_ERROR: successful operation
    124      *  - NO_INIT: audio server or audio hardware not initialized
    125      *  - BAD_VALUE: unsupported configuration
    126      */
    127 
    128     static status_t getMinFrameCount(size_t* frameCount,
    129                                      audio_stream_type_t streamType,
    130                                      uint32_t sampleRate);
    131 
    132     /* How data is transferred to AudioTrack
    133      */
    134     enum transfer_type {
    135         TRANSFER_DEFAULT,   // not specified explicitly; determine from the other parameters
    136         TRANSFER_CALLBACK,  // callback EVENT_MORE_DATA
    137         TRANSFER_OBTAIN,    // FIXME deprecated: call obtainBuffer() and releaseBuffer()
    138         TRANSFER_SYNC,      // synchronous write()
    139         TRANSFER_SHARED,    // shared memory
    140     };
    141 
    142     /* Constructs an uninitialized AudioTrack. No connection with
    143      * AudioFlinger takes place.  Use set() after this.
    144      */
    145                         AudioTrack();
    146 
    147     /* Creates an AudioTrack object and registers it with AudioFlinger.
    148      * Once created, the track needs to be started before it can be used.
    149      * Unspecified values are set to appropriate default values.
    150      * With this constructor, the track is configured for streaming mode.
    151      * Data to be rendered is supplied by write() or by the callback EVENT_MORE_DATA.
    152      * Intermixing a combination of write() and non-ignored EVENT_MORE_DATA is not allowed.
    153      *
    154      * Parameters:
    155      *
    156      * streamType:         Select the type of audio stream this track is attached to
    157      *                     (e.g. AUDIO_STREAM_MUSIC).
    158      * sampleRate:         Data source sampling rate in Hz.
    159      * format:             Audio format (e.g AUDIO_FORMAT_PCM_16_BIT for signed
    160      *                     16 bits per sample).
    161      * channelMask:        Channel mask.
    162      * frameCount:         Minimum size of track PCM buffer in frames. This defines the
    163      *                     application's contribution to the
    164      *                     latency of the track. The actual size selected by the AudioTrack could be
    165      *                     larger if the requested size is not compatible with current audio HAL
    166      *                     configuration.  Zero means to use a default value.
    167      * flags:              See comments on audio_output_flags_t in <system/audio.h>.
    168      * cbf:                Callback function. If not null, this function is called periodically
    169      *                     to provide new data and inform of marker, position updates, etc.
    170      * user:               Context for use by the callback receiver.
    171      * notificationFrames: The callback function is called each time notificationFrames PCM
    172      *                     frames have been consumed from track input buffer.
    173      *                     This is expressed in units of frames at the initial source sample rate.
    174      * sessionId:          Specific session ID, or zero to use default.
    175      * transferType:       How data is transferred to AudioTrack.
    176      * threadCanCallJava:  Not present in parameter list, and so is fixed at false.
    177      */
    178 
    179                         AudioTrack( audio_stream_type_t streamType,
    180                                     uint32_t sampleRate,
    181                                     audio_format_t format,
    182                                     audio_channel_mask_t,
    183                                     int frameCount       = 0,
    184                                     audio_output_flags_t flags = AUDIO_OUTPUT_FLAG_NONE,
    185                                     callback_t cbf       = NULL,
    186                                     void* user           = NULL,
    187                                     int notificationFrames = 0,
    188                                     int sessionId        = 0,
    189                                     transfer_type transferType = TRANSFER_DEFAULT,
    190                                     const audio_offload_info_t *offloadInfo = NULL);
    191 
    192     /* Creates an audio track and registers it with AudioFlinger.
    193      * With this constructor, the track is configured for static buffer mode.
    194      * The format must not be 8-bit linear PCM.
    195      * Data to be rendered is passed in a shared memory buffer
    196      * identified by the argument sharedBuffer, which must be non-0.
    197      * The memory should be initialized to the desired data before calling start().
    198      * The write() method is not supported in this case.
    199      * It is recommended to pass a callback function to be notified of playback end by an
    200      * EVENT_UNDERRUN event.
    201      */
    202 
    203                         AudioTrack( audio_stream_type_t streamType,
    204                                     uint32_t sampleRate,
    205                                     audio_format_t format,
    206                                     audio_channel_mask_t channelMask,
    207                                     const sp<IMemory>& sharedBuffer,
    208                                     audio_output_flags_t flags = AUDIO_OUTPUT_FLAG_NONE,
    209                                     callback_t cbf      = NULL,
    210                                     void* user          = NULL,
    211                                     int notificationFrames = 0,
    212                                     int sessionId       = 0,
    213                                     transfer_type transferType = TRANSFER_DEFAULT,
    214                                     const audio_offload_info_t *offloadInfo = NULL);
    215 
    216     /* Terminates the AudioTrack and unregisters it from AudioFlinger.
    217      * Also destroys all resources associated with the AudioTrack.
    218      */
    219 protected:
    220                         virtual ~AudioTrack();
    221 public:
    222 
    223     /* Initialize an AudioTrack that was created using the AudioTrack() constructor.
    224      * Don't call set() more than once, or after the AudioTrack() constructors that take parameters.
    225      * Returned status (from utils/Errors.h) can be:
    226      *  - NO_ERROR: successful initialization
    227      *  - INVALID_OPERATION: AudioTrack is already initialized
    228      *  - BAD_VALUE: invalid parameter (channelMask, format, sampleRate...)
    229      *  - NO_INIT: audio server or audio hardware not initialized
    230      * If status is not equal to NO_ERROR, don't call any other APIs on this AudioTrack.
    231      * If sharedBuffer is non-0, the frameCount parameter is ignored and
    232      * replaced by the shared buffer's total allocated size in frame units.
    233      *
    234      * Parameters not listed in the AudioTrack constructors above:
    235      *
    236      * threadCanCallJava:  Whether callbacks are made from an attached thread and thus can call JNI.
    237      */
    238             status_t    set(audio_stream_type_t streamType,
    239                             uint32_t sampleRate,
    240                             audio_format_t format,
    241                             audio_channel_mask_t channelMask,
    242                             int frameCount      = 0,
    243                             audio_output_flags_t flags = AUDIO_OUTPUT_FLAG_NONE,
    244                             callback_t cbf      = NULL,
    245                             void* user          = NULL,
    246                             int notificationFrames = 0,
    247                             const sp<IMemory>& sharedBuffer = 0,
    248                             bool threadCanCallJava = false,
    249                             int sessionId       = 0,
    250                             transfer_type transferType = TRANSFER_DEFAULT,
    251                             const audio_offload_info_t *offloadInfo = NULL);
    252 
    253     /* Result of constructing the AudioTrack. This must be checked for successful initialization
    254      * before using any AudioTrack API (except for set()), because using
    255      * an uninitialized AudioTrack produces undefined results.
    256      * See set() method above for possible return codes.
    257      */
    258             status_t    initCheck() const   { return mStatus; }
    259 
    260     /* Returns this track's estimated latency in milliseconds.
    261      * This includes the latency due to AudioTrack buffer size, AudioMixer (if any)
    262      * and audio hardware driver.
    263      */
    264             uint32_t    latency() const     { return mLatency; }
    265 
    266     /* getters, see constructors and set() */
    267 
    268             audio_stream_type_t streamType() const { return mStreamType; }
    269             audio_format_t format() const   { return mFormat; }
    270 
    271     /* Return frame size in bytes, which for linear PCM is
    272      * channelCount * (bit depth per channel / 8).
    273      * channelCount is determined from channelMask, and bit depth comes from format.
    274      * For non-linear formats, the frame size is typically 1 byte.
    275      */
    276             size_t      frameSize() const   { return mFrameSize; }
    277 
    278             uint32_t    channelCount() const { return mChannelCount; }
    279             uint32_t    frameCount() const  { return mFrameCount; }
    280 
    281     /* Return the static buffer specified in constructor or set(), or 0 for streaming mode */
    282             sp<IMemory> sharedBuffer() const { return mSharedBuffer; }
    283 
    284     /* After it's created the track is not active. Call start() to
    285      * make it active. If set, the callback will start being called.
    286      * If the track was previously paused, volume is ramped up over the first mix buffer.
    287      */
    288             status_t        start();
    289 
    290     /* Stop a track.
    291      * In static buffer mode, the track is stopped immediately.
    292      * In streaming mode, the callback will cease being called.  Note that obtainBuffer() still
    293      * works and will fill up buffers until the pool is exhausted, and then will return WOULD_BLOCK.
    294      * In streaming mode the stop does not occur immediately: any data remaining in the buffer
    295      * is first drained, mixed, and output, and only then is the track marked as stopped.
    296      */
    297             void        stop();
    298             bool        stopped() const;
    299 
    300     /* Flush a stopped or paused track. All previously buffered data is discarded immediately.
    301      * This has the effect of draining the buffers without mixing or output.
    302      * Flush is intended for streaming mode, for example before switching to non-contiguous content.
    303      * This function is a no-op if the track is not stopped or paused, or uses a static buffer.
    304      */
    305             void        flush();
    306 
    307     /* Pause a track. After pause, the callback will cease being called and
    308      * obtainBuffer returns WOULD_BLOCK. Note that obtainBuffer() still works
    309      * and will fill up buffers until the pool is exhausted.
    310      * Volume is ramped down over the next mix buffer following the pause request,
    311      * and then the track is marked as paused.  It can be resumed with ramp up by start().
    312      */
    313             void        pause();
    314 
    315     /* Set volume for this track, mostly used for games' sound effects
    316      * left and right volumes. Levels must be >= 0.0 and <= 1.0.
    317      * This is the older API.  New applications should use setVolume(float) when possible.
    318      */
    319             status_t    setVolume(float left, float right);
    320 
    321     /* Set volume for all channels.  This is the preferred API for new applications,
    322      * especially for multi-channel content.
    323      */
    324             status_t    setVolume(float volume);
    325 
    326     /* Set the send level for this track. An auxiliary effect should be attached
    327      * to the track with attachEffect(). Level must be >= 0.0 and <= 1.0.
    328      */
    329             status_t    setAuxEffectSendLevel(float level);
    330             void        getAuxEffectSendLevel(float* level) const;
    331 
    332     /* Set source sample rate for this track in Hz, mostly used for games' sound effects
    333      */
    334             status_t    setSampleRate(uint32_t sampleRate);
    335 
    336     /* Return current source sample rate in Hz, or 0 if unknown */
    337             uint32_t    getSampleRate() const;
    338 
    339     /* Enables looping and sets the start and end points of looping.
    340      * Only supported for static buffer mode.
    341      *
    342      * Parameters:
    343      *
    344      * loopStart:   loop start in frames relative to start of buffer.
    345      * loopEnd:     loop end in frames relative to start of buffer.
    346      * loopCount:   number of loops to execute. Calling setLoop() with loopCount == 0 cancels any
    347      *              pending or active loop. loopCount == -1 means infinite looping.
    348      *
    349      * For proper operation the following condition must be respected:
    350      *      loopCount != 0 implies 0 <= loopStart < loopEnd <= frameCount().
    351      *
    352      * If the loop period (loopEnd - loopStart) is too small for the implementation to support,
    353      * setLoop() will return BAD_VALUE.  loopCount must be >= -1.
    354      *
    355      */
    356             status_t    setLoop(uint32_t loopStart, uint32_t loopEnd, int loopCount);
    357 
    358     /* Sets marker position. When playback reaches the number of frames specified, a callback with
    359      * event type EVENT_MARKER is called. Calling setMarkerPosition with marker == 0 cancels marker
    360      * notification callback.  To set a marker at a position which would compute as 0,
    361      * a workaround is to the set the marker at a nearby position such as ~0 or 1.
    362      * If the AudioTrack has been opened with no callback function associated, the operation will
    363      * fail.
    364      *
    365      * Parameters:
    366      *
    367      * marker:   marker position expressed in wrapping (overflow) frame units,
    368      *           like the return value of getPosition().
    369      *
    370      * Returned status (from utils/Errors.h) can be:
    371      *  - NO_ERROR: successful operation
    372      *  - INVALID_OPERATION: the AudioTrack has no callback installed.
    373      */
    374             status_t    setMarkerPosition(uint32_t marker);
    375             status_t    getMarkerPosition(uint32_t *marker) const;
    376 
    377     /* Sets position update period. Every time the number of frames specified has been played,
    378      * a callback with event type EVENT_NEW_POS is called.
    379      * Calling setPositionUpdatePeriod with updatePeriod == 0 cancels new position notification
    380      * callback.
    381      * If the AudioTrack has been opened with no callback function associated, the operation will
    382      * fail.
    383      * Extremely small values may be rounded up to a value the implementation can support.
    384      *
    385      * Parameters:
    386      *
    387      * updatePeriod:  position update notification period expressed in frames.
    388      *
    389      * Returned status (from utils/Errors.h) can be:
    390      *  - NO_ERROR: successful operation
    391      *  - INVALID_OPERATION: the AudioTrack has no callback installed.
    392      */
    393             status_t    setPositionUpdatePeriod(uint32_t updatePeriod);
    394             status_t    getPositionUpdatePeriod(uint32_t *updatePeriod) const;
    395 
    396     /* Sets playback head position.
    397      * Only supported for static buffer mode.
    398      *
    399      * Parameters:
    400      *
    401      * position:  New playback head position in frames relative to start of buffer.
    402      *            0 <= position <= frameCount().  Note that end of buffer is permitted,
    403      *            but will result in an immediate underrun if started.
    404      *
    405      * Returned status (from utils/Errors.h) can be:
    406      *  - NO_ERROR: successful operation
    407      *  - INVALID_OPERATION: the AudioTrack is not stopped or paused, or is streaming mode.
    408      *  - BAD_VALUE: The specified position is beyond the number of frames present in AudioTrack
    409      *               buffer
    410      */
    411             status_t    setPosition(uint32_t position);
    412 
    413     /* Return the total number of frames played since playback start.
    414      * The counter will wrap (overflow) periodically, e.g. every ~27 hours at 44.1 kHz.
    415      * It is reset to zero by flush(), reload(), and stop().
    416      *
    417      * Parameters:
    418      *
    419      *  position:  Address where to return play head position.
    420      *
    421      * Returned status (from utils/Errors.h) can be:
    422      *  - NO_ERROR: successful operation
    423      *  - BAD_VALUE:  position is NULL
    424      */
    425             status_t    getPosition(uint32_t *position) const;
    426 
    427     /* For static buffer mode only, this returns the current playback position in frames
    428      * relative to start of buffer.  It is analogous to the position units used by
    429      * setLoop() and setPosition().  After underrun, the position will be at end of buffer.
    430      */
    431             status_t    getBufferPosition(uint32_t *position);
    432 
    433     /* Forces AudioTrack buffer full condition. When playing a static buffer, this method avoids
    434      * rewriting the buffer before restarting playback after a stop.
    435      * This method must be called with the AudioTrack in paused or stopped state.
    436      * Not allowed in streaming mode.
    437      *
    438      * Returned status (from utils/Errors.h) can be:
    439      *  - NO_ERROR: successful operation
    440      *  - INVALID_OPERATION: the AudioTrack is not stopped or paused, or is streaming mode.
    441      */
    442             status_t    reload();
    443 
    444     /* Returns a handle on the audio output used by this AudioTrack.
    445      *
    446      * Parameters:
    447      *  none.
    448      *
    449      * Returned value:
    450      *  handle on audio hardware output
    451      */
    452             audio_io_handle_t    getOutput();
    453 
    454     /* Returns the unique session ID associated with this track.
    455      *
    456      * Parameters:
    457      *  none.
    458      *
    459      * Returned value:
    460      *  AudioTrack session ID.
    461      */
    462             int    getSessionId() const { return mSessionId; }
    463 
    464     /* Attach track auxiliary output to specified effect. Use effectId = 0
    465      * to detach track from effect.
    466      *
    467      * Parameters:
    468      *
    469      * effectId:  effectId obtained from AudioEffect::id().
    470      *
    471      * Returned status (from utils/Errors.h) can be:
    472      *  - NO_ERROR: successful operation
    473      *  - INVALID_OPERATION: the effect is not an auxiliary effect.
    474      *  - BAD_VALUE: The specified effect ID is invalid
    475      */
    476             status_t    attachAuxEffect(int effectId);
    477 
    478     /* Obtains a buffer of up to "audioBuffer->frameCount" empty slots for frames.
    479      * After filling these slots with data, the caller should release them with releaseBuffer().
    480      * If the track buffer is not full, obtainBuffer() returns as many contiguous
    481      * [empty slots for] frames as are available immediately.
    482      * If the track buffer is full and track is stopped, obtainBuffer() returns WOULD_BLOCK
    483      * regardless of the value of waitCount.
    484      * If the track buffer is full and track is not stopped, obtainBuffer() blocks with a
    485      * maximum timeout based on waitCount; see chart below.
    486      * Buffers will be returned until the pool
    487      * is exhausted, at which point obtainBuffer() will either block
    488      * or return WOULD_BLOCK depending on the value of the "waitCount"
    489      * parameter.
    490      * Each sample is 16-bit signed PCM.
    491      *
    492      * obtainBuffer() and releaseBuffer() are deprecated for direct use by applications,
    493      * which should use write() or callback EVENT_MORE_DATA instead.
    494      *
    495      * Interpretation of waitCount:
    496      *  +n  limits wait time to n * WAIT_PERIOD_MS,
    497      *  -1  causes an (almost) infinite wait time,
    498      *   0  non-blocking.
    499      *
    500      * Buffer fields
    501      * On entry:
    502      *  frameCount  number of frames requested
    503      * After error return:
    504      *  frameCount  0
    505      *  size        0
    506      *  raw         undefined
    507      * After successful return:
    508      *  frameCount  actual number of frames available, <= number requested
    509      *  size        actual number of bytes available
    510      *  raw         pointer to the buffer
    511      */
    512 
    513     /* FIXME Deprecated public API for TRANSFER_OBTAIN mode */
    514             status_t    obtainBuffer(Buffer* audioBuffer, int32_t waitCount)
    515                                 __attribute__((__deprecated__));
    516 
    517 private:
    518     /* If nonContig is non-NULL, it is an output parameter that will be set to the number of
    519      * additional non-contiguous frames that are available immediately.
    520      * FIXME We could pass an array of Buffers instead of only one Buffer to obtainBuffer(),
    521      * in case the requested amount of frames is in two or more non-contiguous regions.
    522      * FIXME requested and elapsed are both relative times.  Consider changing to absolute time.
    523      */
    524             status_t    obtainBuffer(Buffer* audioBuffer, const struct timespec *requested,
    525                                      struct timespec *elapsed = NULL, size_t *nonContig = NULL);
    526 public:
    527 
    528 //EL_FIXME to be reconciled with new obtainBuffer() return codes and control block proxy
    529 //            enum {
    530 //            NO_MORE_BUFFERS = 0x80000001,   // same name in AudioFlinger.h, ok to be different value
    531 //            TEAR_DOWN       = 0x80000002,
    532 //            STOPPED = 1,
    533 //            STREAM_END_WAIT,
    534 //            STREAM_END
    535 //        };
    536 
    537     /* Release a filled buffer of "audioBuffer->frameCount" frames for AudioFlinger to process. */
    538     // FIXME make private when obtainBuffer() for TRANSFER_OBTAIN is removed
    539             void        releaseBuffer(Buffer* audioBuffer);
    540 
    541     /* As a convenience we provide a write() interface to the audio buffer.
    542      * Input parameter 'size' is in byte units.
    543      * This is implemented on top of obtainBuffer/releaseBuffer. For best
    544      * performance use callbacks. Returns actual number of bytes written >= 0,
    545      * or one of the following negative status codes:
    546      *      INVALID_OPERATION   AudioTrack is configured for static buffer or streaming mode
    547      *      BAD_VALUE           size is invalid
    548      *      WOULD_BLOCK         when obtainBuffer() returns same, or
    549      *                          AudioTrack was stopped during the write
    550      *      or any other error code returned by IAudioTrack::start() or restoreTrack_l().
    551      */
    552             ssize_t     write(const void* buffer, size_t size);
    553 
    554     /*
    555      * Dumps the state of an audio track.
    556      */
    557             status_t    dump(int fd, const Vector<String16>& args) const;
    558 
    559     /*
    560      * Return the total number of frames which AudioFlinger desired but were unavailable,
    561      * and thus which resulted in an underrun.  Reset to zero by stop().
    562      */
    563             uint32_t    getUnderrunFrames() const;
    564 
    565     /* Get the flags */
    566             audio_output_flags_t getFlags() const { return mFlags; }
    567 
    568     /* Set parameters - only possible when using direct output */
    569             status_t    setParameters(const String8& keyValuePairs);
    570 
    571     /* Get parameters */
    572             String8     getParameters(const String8& keys);
    573 
    574     /* Poll for a timestamp on demand.
    575      * Use if EVENT_NEW_TIMESTAMP is not delivered often enough for your needs,
    576      * or if you need to get the most recent timestamp outside of the event callback handler.
    577      * Caution: calling this method too often may be inefficient;
    578      * if you need a high resolution mapping between frame position and presentation time,
    579      * consider implementing that at application level, based on the low resolution timestamps.
    580      * Returns NO_ERROR if timestamp is valid.
    581      */
    582             status_t    getTimestamp(AudioTimestamp& timestamp);
    583 
    584 protected:
    585     /* copying audio tracks is not allowed */
    586                         AudioTrack(const AudioTrack& other);
    587             AudioTrack& operator = (const AudioTrack& other);
    588 
    589     /* a small internal class to handle the callback */
    590     class AudioTrackThread : public Thread
    591     {
    592     public:
    593         AudioTrackThread(AudioTrack& receiver, bool bCanCallJava = false);
    594 
    595         // Do not call Thread::requestExitAndWait() without first calling requestExit().
    596         // Thread::requestExitAndWait() is not virtual, and the implementation doesn't do enough.
    597         virtual void        requestExit();
    598 
    599                 void        pause();    // suspend thread from execution at next loop boundary
    600                 void        resume();   // allow thread to execute, if not requested to exit
    601 
    602     private:
    603                 void        pauseInternal(nsecs_t ns = 0LL);
    604                                         // like pause(), but only used internally within thread
    605 
    606         friend class AudioTrack;
    607         virtual bool        threadLoop();
    608         AudioTrack&         mReceiver;
    609         virtual ~AudioTrackThread();
    610         Mutex               mMyLock;    // Thread::mLock is private
    611         Condition           mMyCond;    // Thread::mThreadExitedCondition is private
    612         bool                mPaused;    // whether thread is requested to pause at next loop entry
    613         bool                mPausedInt; // whether thread internally requests pause
    614         nsecs_t             mPausedNs;  // if mPausedInt then associated timeout, otherwise ignored
    615         bool                mIgnoreNextPausedInt;   // whether to ignore next mPausedInt request
    616     };
    617 
    618             // body of AudioTrackThread::threadLoop()
    619             // returns the maximum amount of time before we would like to run again, where:
    620             //      0           immediately
    621             //      > 0         no later than this many nanoseconds from now
    622             //      NS_WHENEVER still active but no particular deadline
    623             //      NS_INACTIVE inactive so don't run again until re-started
    624             //      NS_NEVER    never again
    625             static const nsecs_t NS_WHENEVER = -1, NS_INACTIVE = -2, NS_NEVER = -3;
    626             nsecs_t processAudioBuffer(const sp<AudioTrackThread>& thread);
    627             status_t processStreamEnd(int32_t waitCount);
    628 
    629 
    630             // caller must hold lock on mLock for all _l methods
    631 
    632             status_t createTrack_l(audio_stream_type_t streamType,
    633                                  uint32_t sampleRate,
    634                                  audio_format_t format,
    635                                  size_t frameCount,
    636                                  audio_output_flags_t flags,
    637                                  const sp<IMemory>& sharedBuffer,
    638                                  audio_io_handle_t output,
    639                                  size_t epoch);
    640 
    641             // can only be called when mState != STATE_ACTIVE
    642             void flush_l();
    643 
    644             void setLoop_l(uint32_t loopStart, uint32_t loopEnd, int loopCount);
    645             audio_io_handle_t getOutput_l();
    646 
    647             // FIXME enum is faster than strcmp() for parameter 'from'
    648             status_t restoreTrack_l(const char *from);
    649 
    650             bool     isOffloaded() const
    651                 { return (mFlags & AUDIO_OUTPUT_FLAG_COMPRESS_OFFLOAD) != 0; }
    652 
    653     // Next 3 fields may be changed if IAudioTrack is re-created, but always != 0
    654     sp<IAudioTrack>         mAudioTrack;
    655     sp<IMemory>             mCblkMemory;
    656     audio_track_cblk_t*     mCblk;                  // re-load after mLock.unlock()
    657 
    658     sp<AudioTrackThread>    mAudioTrackThread;
    659     float                   mVolume[2];
    660     float                   mSendLevel;
    661     uint32_t                mSampleRate;
    662     size_t                  mFrameCount;            // corresponds to current IAudioTrack
    663     size_t                  mReqFrameCount;         // frame count to request the next time a new
    664                                                     // IAudioTrack is needed
    665 
    666 
    667     // constant after constructor or set()
    668     audio_format_t          mFormat;                // as requested by client, not forced to 16-bit
    669     audio_stream_type_t     mStreamType;
    670     uint32_t                mChannelCount;
    671     audio_channel_mask_t    mChannelMask;
    672     transfer_type           mTransfer;
    673 
    674     // mFrameSize is equal to mFrameSizeAF for non-PCM or 16-bit PCM data.  For 8-bit PCM data, it's
    675     // twice as large as mFrameSize because data is expanded to 16-bit before it's stored in buffer.
    676     size_t                  mFrameSize;             // app-level frame size
    677     size_t                  mFrameSizeAF;           // AudioFlinger frame size
    678 
    679     status_t                mStatus;
    680 
    681     // can change dynamically when IAudioTrack invalidated
    682     uint32_t                mLatency;               // in ms
    683 
    684     // Indicates the current track state.  Protected by mLock.
    685     enum State {
    686         STATE_ACTIVE,
    687         STATE_STOPPED,
    688         STATE_PAUSED,
    689         STATE_PAUSED_STOPPING,
    690         STATE_FLUSHED,
    691         STATE_STOPPING,
    692     }                       mState;
    693 
    694     // for client callback handler
    695     callback_t              mCbf;                   // callback handler for events, or NULL
    696     void*                   mUserData;
    697 
    698     // for notification APIs
    699     uint32_t                mNotificationFramesReq; // requested number of frames between each
    700                                                     // notification callback,
    701                                                     // at initial source sample rate
    702     uint32_t                mNotificationFramesAct; // actual number of frames between each
    703                                                     // notification callback,
    704                                                     // at initial source sample rate
    705     bool                    mRefreshRemaining;      // processAudioBuffer() should refresh next 2
    706 
    707     // These are private to processAudioBuffer(), and are not protected by a lock
    708     uint32_t                mRemainingFrames;       // number of frames to request in obtainBuffer()
    709     bool                    mRetryOnPartialBuffer;  // sleep and retry after partial obtainBuffer()
    710     uint32_t                mObservedSequence;      // last observed value of mSequence
    711 
    712     sp<IMemory>             mSharedBuffer;
    713     uint32_t                mLoopPeriod;            // in frames, zero means looping is disabled
    714     uint32_t                mMarkerPosition;        // in wrapping (overflow) frame units
    715     bool                    mMarkerReached;
    716     uint32_t                mNewPosition;           // in frames
    717     uint32_t                mUpdatePeriod;          // in frames, zero means no EVENT_NEW_POS
    718 
    719     audio_output_flags_t    mFlags;
    720     int                     mSessionId;
    721     int                     mAuxEffectId;
    722 
    723     mutable Mutex           mLock;
    724 
    725     bool                    mIsTimed;
    726     int                     mPreviousPriority;          // before start()
    727     SchedPolicy             mPreviousSchedulingGroup;
    728     bool                    mAwaitBoost;    // thread should wait for priority boost before running
    729 
    730     // The proxy should only be referenced while a lock is held because the proxy isn't
    731     // multi-thread safe, especially the SingleStateQueue part of the proxy.
    732     // An exception is that a blocking ClientProxy::obtainBuffer() may be called without a lock,
    733     // provided that the caller also holds an extra reference to the proxy and shared memory to keep
    734     // them around in case they are replaced during the obtainBuffer().
    735     sp<StaticAudioTrackClientProxy> mStaticProxy;   // for type safety only
    736     sp<AudioTrackClientProxy>       mProxy;         // primary owner of the memory
    737 
    738     bool                    mInUnderrun;            // whether track is currently in underrun state
    739     String8                 mName;                  // server's name for this IAudioTrack
    740 
    741 private:
    742     class DeathNotifier : public IBinder::DeathRecipient {
    743     public:
    744         DeathNotifier(AudioTrack* audioTrack) : mAudioTrack(audioTrack) { }
    745     protected:
    746         virtual void        binderDied(const wp<IBinder>& who);
    747     private:
    748         const wp<AudioTrack> mAudioTrack;
    749     };
    750 
    751     sp<DeathNotifier>       mDeathNotifier;
    752     uint32_t                mSequence;              // incremented for each new IAudioTrack attempt
    753     audio_io_handle_t       mOutput;                // cached output io handle
    754 };
    755 
    756 class TimedAudioTrack : public AudioTrack
    757 {
    758 public:
    759     TimedAudioTrack();
    760 
    761     /* allocate a shared memory buffer that can be passed to queueTimedBuffer */
    762     status_t allocateTimedBuffer(size_t size, sp<IMemory>* buffer);
    763 
    764     /* queue a buffer obtained via allocateTimedBuffer for playback at the
    765        given timestamp.  PTS units are microseconds on the media time timeline.
    766        The media time transform (set with setMediaTimeTransform) set by the
    767        audio producer will handle converting from media time to local time
    768        (perhaps going through the common time timeline in the case of
    769        synchronized multiroom audio case) */
    770     status_t queueTimedBuffer(const sp<IMemory>& buffer, int64_t pts);
    771 
    772     /* define a transform between media time and either common time or
    773        local time */
    774     enum TargetTimeline {LOCAL_TIME, COMMON_TIME};
    775     status_t setMediaTimeTransform(const LinearTransform& xform,
    776                                    TargetTimeline target);
    777 };
    778 
    779 }; // namespace android
    780 
    781 #endif // ANDROID_AUDIOTRACK_H
    782