NBAIO.h revision f95a3c4122d67273d930c7d83c3df99f136603ed
1/* 2 * Copyright (C) 2012 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_AUDIO_NBAIO_H 18#define ANDROID_AUDIO_NBAIO_H 19 20// Non-blocking audio I/O interface 21// 22// This header file has the abstract interfaces only. Concrete implementation classes are declared 23// elsewhere. Implementations _should_ be non-blocking for all methods, especially read() and 24// write(), but this is not enforced. In general, implementations do not need to be multi-thread 25// safe, and any exceptions are noted in the particular implementation. 26 27#include <limits.h> 28#include <stdlib.h> 29#include <utils/Errors.h> 30#include <utils/RefBase.h> 31#include <media/AudioTimestamp.h> 32#include <system/audio.h> 33 34namespace android { 35 36// In addition to the usual status_t 37enum { 38 NEGOTIATE = 0x80000010, // Must (re-)negotiate format. For negotiate() only, the offeree 39 // doesn't accept offers, and proposes counter-offers 40 OVERRUN = 0x80000011, // availableToRead(), read(), or readVia() detected lost input due 41 // to overrun; an event is counted and the caller should re-try 42 UNDERRUN = 0x80000012, // availableToWrite(), write(), or writeVia() detected a gap in 43 // output due to underrun (not being called often enough, or with 44 // enough data); an event is counted and the caller should re-try 45}; 46 47// Negotiation of format is based on the data provider and data sink, or the data consumer and 48// data source, exchanging prioritized arrays of offers and counter-offers until a single offer is 49// mutually agreed upon. Each offer is an NBAIO_Format. For simplicity and performance, 50// NBAIO_Format is a typedef that ties together the most important combinations of the various 51// attributes, rather than a struct with separate fields for format, sample rate, channel count, 52// interleave, packing, alignment, etc. The reason is that NBAIO_Format tries to abstract out only 53// the combinations that are actually needed within AudioFlinger. If the list of combinations grows 54// too large, then this decision should be re-visited. 55// Sample rate and channel count are explicit, PCM interleaved 16-bit is assumed. 56struct NBAIO_Format { 57//private: 58 unsigned mPacked; 59}; 60 61extern const NBAIO_Format Format_Invalid; 62 63// Return the frame size of an NBAIO_Format in bytes 64size_t Format_frameSize(const NBAIO_Format& format); 65 66// Return the frame size of an NBAIO_Format as a bit shift 67// or -1 if frame size is not a power of 2 68int Format_frameBitShift(const NBAIO_Format& format); 69 70// Convert a sample rate in Hz and channel count to an NBAIO_Format 71// FIXME Remove the default value of AUDIO_FORMAT_PCM_16_BIT, and rename 72NBAIO_Format Format_from_SR_C(unsigned sampleRate, unsigned channelCount, 73 audio_format_t format = AUDIO_FORMAT_PCM_16_BIT); 74 75// Return the sample rate in Hz of an NBAIO_Format 76unsigned Format_sampleRate(const NBAIO_Format& format); 77 78// Return the channel count of an NBAIO_Format 79unsigned Format_channelCount(const NBAIO_Format& format); 80 81// Callbacks used by NBAIO_Sink::writeVia() and NBAIO_Source::readVia() below. 82typedef ssize_t (*writeVia_t)(void *user, void *buffer, size_t count); 83typedef ssize_t (*readVia_t)(void *user, const void *buffer, 84 size_t count, int64_t readPTS); 85 86// Check whether an NBAIO_Format is valid 87bool Format_isValid(const NBAIO_Format& format); 88 89// Compare two NBAIO_Format values 90bool Format_isEqual(const NBAIO_Format& format1, const NBAIO_Format& format2); 91 92// Abstract class (interface) representing a data port. 93class NBAIO_Port : public RefBase { 94 95public: 96 97 // negotiate() must called first. The purpose of negotiate() is to check compatibility of 98 // formats, not to automatically adapt if they are incompatible. It's the responsibility of 99 // whoever sets up the graph connections to make sure formats are compatible, and this method 100 // just verifies that. The edges are "dumb" and don't attempt to adapt to bad connections. 101 // How it works: offerer proposes an array of formats, in descending order of preference from 102 // offers[0] to offers[numOffers - 1]. If offeree accepts one of these formats, it returns 103 // the index of that offer. Otherwise, offeree sets numCounterOffers to the number of 104 // counter-offers (up to a maximumum of the entry value of numCounterOffers), fills in the 105 // provided array counterOffers[] with its counter-offers, in descending order of preference 106 // from counterOffers[0] to counterOffers[numCounterOffers - 1], and returns NEGOTIATE. 107 // Note that since the offerer allocates space for counter-offers, but only the offeree knows 108 // how many counter-offers it has, there may be insufficient space for all counter-offers. 109 // In that case, the offeree sets numCounterOffers to the requested number of counter-offers 110 // (which is greater than the entry value of numCounterOffers), fills in as many of the most 111 // important counterOffers as will fit, and returns NEGOTIATE. As this implies a re-allocation, 112 // it should be used as a last resort. It is preferable for the offerer to simply allocate a 113 // larger space to begin with, and/or for the offeree to tolerate a smaller space than desired. 114 // Alternatively, the offerer can pass NULL for offers and counterOffers, and zero for 115 // numOffers. This indicates that it has not allocated space for any counter-offers yet. 116 // In this case, the offerree should set numCounterOffers appropriately and return NEGOTIATE. 117 // Then the offerer will allocate the correct amount of memory and retry. 118 // Format_Invalid is not allowed as either an offer or counter-offer. 119 // Returns: 120 // >= 0 Offer accepted. 121 // NEGOTIATE No offer accepted, and counter-offer(s) optionally made. See above for details. 122 virtual ssize_t negotiate(const NBAIO_Format offers[], size_t numOffers, 123 NBAIO_Format counterOffers[], size_t& numCounterOffers); 124 125 // Return the current negotiated format, or Format_Invalid if negotiation has not been done, 126 // or if re-negotiation is required. 127 virtual NBAIO_Format format() const { return mNegotiated ? mFormat : Format_Invalid; } 128 129protected: 130 NBAIO_Port(const NBAIO_Format& format) : mNegotiated(false), mFormat(format), 131 mBitShift(Format_frameBitShift(format)), 132 mFrameSize(Format_frameSize(format)) { } 133 virtual ~NBAIO_Port() { } 134 135 // Implementations are free to ignore these if they don't need them 136 137 bool mNegotiated; // mNegotiated implies (mFormat != Format_Invalid) 138 NBAIO_Format mFormat; // (mFormat != Format_Invalid) does not imply mNegotiated 139 size_t mBitShift; // assign in parallel with any assignment to mFormat 140 size_t mFrameSize; // assign in parallel with any assignment to mFormat 141}; 142 143// Abstract class (interface) representing a non-blocking data sink, for use by a data provider. 144class NBAIO_Sink : public NBAIO_Port { 145 146public: 147 148 // For the next two APIs: 149 // 32 bits rolls over after 27 hours at 44.1 kHz; if that concerns you then poll periodically. 150 151 // Return the number of frames written successfully since construction. 152 virtual size_t framesWritten() const { return mFramesWritten; } 153 154 // Number of frames lost due to underrun since construction. 155 virtual size_t framesUnderrun() const { return 0; } 156 157 // Number of underruns since construction, where a set of contiguous lost frames is one event. 158 virtual size_t underruns() const { return 0; } 159 160 // Estimate of number of frames that could be written successfully now without blocking. 161 // When a write() is actually attempted, the implementation is permitted to return a smaller or 162 // larger transfer count, however it will make a good faith effort to give an accurate estimate. 163 // Errors: 164 // NEGOTIATE (Re-)negotiation is needed. 165 // UNDERRUN write() has not been called frequently enough, or with enough frames to keep up. 166 // An underrun event is counted, and the caller should re-try this operation. 167 // WOULD_BLOCK Determining how many frames can be written without blocking would itself block. 168 virtual ssize_t availableToWrite() const { return SSIZE_MAX; } 169 170 // Transfer data to sink from single input buffer. Implies a copy. 171 // Inputs: 172 // buffer Non-NULL buffer owned by provider. 173 // count Maximum number of frames to transfer. 174 // Return value: 175 // > 0 Number of frames successfully transferred prior to first error. 176 // = 0 Count was zero. 177 // < 0 status_t error occurred prior to the first frame transfer. 178 // Errors: 179 // NEGOTIATE (Re-)negotiation is needed. 180 // WOULD_BLOCK No frames can be transferred without blocking. 181 // UNDERRUN write() has not been called frequently enough, or with enough frames to keep up. 182 // An underrun event is counted, and the caller should re-try this operation. 183 virtual ssize_t write(const void *buffer, size_t count) = 0; 184 185 // Transfer data to sink using a series of callbacks. More suitable for zero-fill, synthesis, 186 // and non-contiguous transfers (e.g. circular buffer or writev). 187 // Inputs: 188 // via Callback function that the sink will call as many times as needed to consume data. 189 // total Estimate of the number of frames the provider has available. This is an estimate, 190 // and it can provide a different number of frames during the series of callbacks. 191 // user Arbitrary void * reserved for data provider. 192 // block Number of frames per block, that is a suggested value for 'count' in each callback. 193 // Zero means no preference. This parameter is a hint only, and may be ignored. 194 // Return value: 195 // > 0 Total number of frames successfully transferred prior to first error. 196 // = 0 Count was zero. 197 // < 0 status_t error occurred prior to the first frame transfer. 198 // Errors: 199 // NEGOTIATE (Re-)negotiation is needed. 200 // WOULD_BLOCK No frames can be transferred without blocking. 201 // UNDERRUN write() has not been called frequently enough, or with enough frames to keep up. 202 // An underrun event is counted, and the caller should re-try this operation. 203 // 204 // The 'via' callback is called by the data sink as follows: 205 // Inputs: 206 // user Arbitrary void * reserved for data provider. 207 // buffer Non-NULL buffer owned by sink that callback should fill in with data, 208 // up to a maximum of 'count' frames. 209 // count Maximum number of frames to transfer during this callback. 210 // Return value: 211 // > 0 Number of frames successfully transferred during this callback prior to first error. 212 // = 0 Count was zero. 213 // < 0 status_t error occurred prior to the first frame transfer during this callback. 214 virtual ssize_t writeVia(writeVia_t via, size_t total, void *user, size_t block = 0); 215 216 // Get the time (on the LocalTime timeline) at which the first frame of audio of the next write 217 // operation to this sink will be eventually rendered by the HAL. 218 // Inputs: 219 // ts A pointer pointing to the int64_t which will hold the result. 220 // Return value: 221 // OK Everything went well, *ts holds the time at which the first audio frame of the next 222 // write operation will be rendered, or AudioBufferProvider::kInvalidPTS if this sink 223 // does not know the answer for some reason. Sinks which eventually lead to a HAL 224 // which implements get_next_write_timestamp may return Invalid temporarily if the DMA 225 // output of the audio driver has not started yet. Sinks which lead to a HAL which 226 // does not implement get_next_write_timestamp, or which don't lead to a HAL at all, 227 // will always return kInvalidPTS. 228 // <other> Something unexpected happened internally. Check the logs and start debugging. 229 virtual status_t getNextWriteTimestamp(int64_t *ts) { return INVALID_OPERATION; } 230 231 // Returns NO_ERROR if a timestamp is available. The timestamp includes the total number 232 // of frames presented to an external observer, together with the value of CLOCK_MONOTONIC 233 // as of this presentation count. 234 virtual status_t getTimestamp(AudioTimestamp& timestamp) { return INVALID_OPERATION; } 235 236protected: 237 NBAIO_Sink(const NBAIO_Format& format = Format_Invalid) : NBAIO_Port(format), mFramesWritten(0) { } 238 virtual ~NBAIO_Sink() { } 239 240 // Implementations are free to ignore these if they don't need them 241 size_t mFramesWritten; 242}; 243 244// Abstract class (interface) representing a non-blocking data source, for use by a data consumer. 245class NBAIO_Source : public NBAIO_Port { 246 247public: 248 249 // For the next two APIs: 250 // 32 bits rolls over after 27 hours at 44.1 kHz; if that concerns you then poll periodically. 251 252 // Number of frames read successfully since construction. 253 virtual size_t framesRead() const { return mFramesRead; } 254 255 // Number of frames lost due to overrun since construction. 256 // Not const because implementations may need to do I/O. 257 virtual size_t framesOverrun() /*const*/ { return 0; } 258 259 // Number of overruns since construction, where a set of contiguous lost frames is one event. 260 // Not const because implementations may need to do I/O. 261 virtual size_t overruns() /*const*/ { return 0; } 262 263 // Estimate of number of frames that could be read successfully now. 264 // When a read() is actually attempted, the implementation is permitted to return a smaller or 265 // larger transfer count, however it will make a good faith effort to give an accurate estimate. 266 // Errors: 267 // NEGOTIATE (Re-)negotiation is needed. 268 // OVERRUN One or more frames were lost due to overrun, try again to read more recent data. 269 // WOULD_BLOCK Determining how many frames can be read without blocking would itself block. 270 virtual ssize_t availableToRead() { return SSIZE_MAX; } 271 272 // Transfer data from source into single destination buffer. Implies a copy. 273 // Inputs: 274 // buffer Non-NULL destination buffer owned by consumer. 275 // count Maximum number of frames to transfer. 276 // readPTS The presentation time (on the LocalTime timeline) for which data 277 // is being requested, or kInvalidPTS if not known. 278 // Return value: 279 // > 0 Number of frames successfully transferred prior to first error. 280 // = 0 Count was zero. 281 // < 0 status_t error occurred prior to the first frame transfer. 282 // Errors: 283 // NEGOTIATE (Re-)negotiation is needed. 284 // WOULD_BLOCK No frames can be transferred without blocking. 285 // OVERRUN read() has not been called frequently enough, or with enough frames to keep up. 286 // One or more frames were lost due to overrun, try again to read more recent data. 287 virtual ssize_t read(void *buffer, size_t count, int64_t readPTS) = 0; 288 289 // Transfer data from source using a series of callbacks. More suitable for zero-fill, 290 // synthesis, and non-contiguous transfers (e.g. circular buffer or readv). 291 // Inputs: 292 // via Callback function that the source will call as many times as needed to provide data. 293 // total Estimate of the number of frames the consumer desires. This is an estimate, 294 // and it can consume a different number of frames during the series of callbacks. 295 // user Arbitrary void * reserved for data consumer. 296 // readPTS The presentation time (on the LocalTime timeline) for which data 297 // is being requested, or kInvalidPTS if not known. 298 // block Number of frames per block, that is a suggested value for 'count' in each callback. 299 // Zero means no preference. This parameter is a hint only, and may be ignored. 300 // Return value: 301 // > 0 Total number of frames successfully transferred prior to first error. 302 // = 0 Count was zero. 303 // < 0 status_t error occurred prior to the first frame transfer. 304 // Errors: 305 // NEGOTIATE (Re-)negotiation is needed. 306 // WOULD_BLOCK No frames can be transferred without blocking. 307 // OVERRUN read() has not been called frequently enough, or with enough frames to keep up. 308 // One or more frames were lost due to overrun, try again to read more recent data. 309 // 310 // The 'via' callback is called by the data source as follows: 311 // Inputs: 312 // user Arbitrary void * reserved for data consumer. 313 // dest Non-NULL buffer owned by source that callback should consume data from, 314 // up to a maximum of 'count' frames. 315 // count Maximum number of frames to transfer during this callback. 316 // Return value: 317 // > 0 Number of frames successfully transferred during this callback prior to first error. 318 // = 0 Count was zero. 319 // < 0 status_t error occurred prior to the first frame transfer during this callback. 320 virtual ssize_t readVia(readVia_t via, size_t total, void *user, 321 int64_t readPTS, size_t block = 0); 322 323 // Invoked asynchronously by corresponding sink when a new timestamp is available. 324 // Default implementation ignores the timestamp. 325 virtual void onTimestamp(const AudioTimestamp& timestamp) { } 326 327protected: 328 NBAIO_Source(const NBAIO_Format& format = Format_Invalid) : NBAIO_Port(format), mFramesRead(0) { } 329 virtual ~NBAIO_Source() { } 330 331 // Implementations are free to ignore these if they don't need them 332 size_t mFramesRead; 333}; 334 335} // namespace android 336 337#endif // ANDROID_AUDIO_NBAIO_H 338