NBAIO.h revision cc1e0e807ee9a9f163a4685cbd6efd6ae55849cf
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 33namespace android { 34 35// In addition to the usual status_t 36enum { 37 NEGOTIATE = 0x80000010, // Must (re-)negotiate format. For negotiate() only, the offeree 38 // doesn't accept offers, and proposes counter-offers 39 OVERRUN = 0x80000011, // availableToRead(), read(), or readVia() detected lost input due 40 // to overrun; an event is counted and the caller should re-try 41 UNDERRUN = 0x80000012, // availableToWrite(), write(), or writeVia() detected a gap in 42 // output due to underrun (not being called often enough, or with 43 // enough data); an event is counted and the caller should re-try 44}; 45 46// Negotiation of format is based on the data provider and data sink, or the data consumer and 47// data source, exchanging prioritized arrays of offers and counter-offers until a single offer is 48// mutually agreed upon. Each offer is an NBAIO_Format. For simplicity and performance, 49// NBAIO_Format is a typedef that ties together the most important combinations of the various 50// attributes, rather than a struct with separate fields for format, sample rate, channel count, 51// interleave, packing, alignment, etc. The reason is that NBAIO_Format tries to abstract out only 52// the combinations that are actually needed within AudioFlinger. If the list of combinations grows 53// too large, then this decision should be re-visited. 54// Sample rate and channel count are explicit, PCM interleaved 16-bit is assumed. 55typedef unsigned NBAIO_Format; 56 57extern const NBAIO_Format Format_Invalid; 58 59// Return the frame size of an NBAIO_Format in bytes 60size_t Format_frameSize(const NBAIO_Format& format); 61 62// Return the frame size of an NBAIO_Format as a bit shift 63size_t Format_frameBitShift(const NBAIO_Format& format); 64 65// Convert a sample rate in Hz and channel count to an NBAIO_Format 66NBAIO_Format Format_from_SR_C(unsigned sampleRate, unsigned channelCount); 67 68// Return the sample rate in Hz of an NBAIO_Format 69unsigned Format_sampleRate(const NBAIO_Format& format); 70 71// Return the channel count of an NBAIO_Format 72unsigned Format_channelCount(const NBAIO_Format& format); 73 74// Callbacks used by NBAIO_Sink::writeVia() and NBAIO_Source::readVia() below. 75typedef ssize_t (*writeVia_t)(void *user, void *buffer, size_t count); 76typedef ssize_t (*readVia_t)(void *user, const void *buffer, 77 size_t count, int64_t readPTS); 78 79// Check whether an NBAIO_Format is valid 80bool Format_isValid(const NBAIO_Format& format); 81 82// Compare two NBAIO_Format values 83bool Format_isEqual(const NBAIO_Format& format1, const NBAIO_Format& format2); 84 85// Abstract class (interface) representing a data port. 86class NBAIO_Port : public RefBase { 87 88public: 89 90 // negotiate() must called first. The purpose of negotiate() is to check compatibility of 91 // formats, not to automatically adapt if they are incompatible. It's the responsibility of 92 // whoever sets up the graph connections to make sure formats are compatible, and this method 93 // just verifies that. The edges are "dumb" and don't attempt to adapt to bad connections. 94 // How it works: offerer proposes an array of formats, in descending order of preference from 95 // offers[0] to offers[numOffers - 1]. If offeree accepts one of these formats, it returns 96 // the index of that offer. Otherwise, offeree sets numCounterOffers to the number of 97 // counter-offers (up to a maximumum of the entry value of numCounterOffers), fills in the 98 // provided array counterOffers[] with its counter-offers, in descending order of preference 99 // from counterOffers[0] to counterOffers[numCounterOffers - 1], and returns NEGOTIATE. 100 // Note that since the offerer allocates space for counter-offers, but only the offeree knows 101 // how many counter-offers it has, there may be insufficient space for all counter-offers. 102 // In that case, the offeree sets numCounterOffers to the requested number of counter-offers 103 // (which is greater than the entry value of numCounterOffers), fills in as many of the most 104 // important counterOffers as will fit, and returns NEGOTIATE. As this implies a re-allocation, 105 // it should be used as a last resort. It is preferable for the offerer to simply allocate a 106 // larger space to begin with, and/or for the offeree to tolerate a smaller space than desired. 107 // Alternatively, the offerer can pass NULL for offers and counterOffers, and zero for 108 // numOffers. This indicates that it has not allocated space for any counter-offers yet. 109 // In this case, the offerree should set numCounterOffers appropriately and return NEGOTIATE. 110 // Then the offerer will allocate the correct amount of memory and retry. 111 // Format_Invalid is not allowed as either an offer or counter-offer. 112 // Returns: 113 // >= 0 Offer accepted. 114 // NEGOTIATE No offer accepted, and counter-offer(s) optionally made. See above for details. 115 virtual ssize_t negotiate(const NBAIO_Format offers[], size_t numOffers, 116 NBAIO_Format counterOffers[], size_t& numCounterOffers); 117 118 // Return the current negotiated format, or Format_Invalid if negotiation has not been done, 119 // or if re-negotiation is required. 120 virtual NBAIO_Format format() const { return mNegotiated ? mFormat : Format_Invalid; } 121 122protected: 123 NBAIO_Port(const NBAIO_Format& format) : mNegotiated(false), mFormat(format), 124 mBitShift(Format_frameBitShift(format)) { } 125 virtual ~NBAIO_Port() { } 126 127 // Implementations are free to ignore these if they don't need them 128 129 bool mNegotiated; // mNegotiated implies (mFormat != Format_Invalid) 130 NBAIO_Format mFormat; // (mFormat != Format_Invalid) does not imply mNegotiated 131 size_t mBitShift; // assign in parallel with any assignment to mFormat 132}; 133 134// Abstract class (interface) representing a non-blocking data sink, for use by a data provider. 135class NBAIO_Sink : public NBAIO_Port { 136 137public: 138 139 // For the next two APIs: 140 // 32 bits rolls over after 27 hours at 44.1 kHz; if that concerns you then poll periodically. 141 142 // Return the number of frames written successfully since construction. 143 virtual size_t framesWritten() const { return mFramesWritten; } 144 145 // Number of frames lost due to underrun since construction. 146 virtual size_t framesUnderrun() const { return 0; } 147 148 // Number of underruns since construction, where a set of contiguous lost frames is one event. 149 virtual size_t underruns() const { return 0; } 150 151 // Estimate of number of frames that could be written successfully now without blocking. 152 // When a write() is actually attempted, the implementation is permitted to return a smaller or 153 // larger transfer count, however it will make a good faith effort to give an accurate estimate. 154 // Errors: 155 // NEGOTIATE (Re-)negotiation is needed. 156 // UNDERRUN write() has not been called frequently enough, or with enough frames to keep up. 157 // An underrun event is counted, and the caller should re-try this operation. 158 // WOULD_BLOCK Determining how many frames can be written without blocking would itself block. 159 virtual ssize_t availableToWrite() const { return SSIZE_MAX; } 160 161 // Transfer data to sink from single input buffer. Implies a copy. 162 // Inputs: 163 // buffer Non-NULL buffer owned by provider. 164 // count Maximum number of frames to transfer. 165 // Return value: 166 // > 0 Number of frames successfully transferred prior to first error. 167 // = 0 Count was zero. 168 // < 0 status_t error occurred prior to the first frame transfer. 169 // Errors: 170 // NEGOTIATE (Re-)negotiation is needed. 171 // WOULD_BLOCK No frames can be transferred without blocking. 172 // UNDERRUN write() has not been called frequently enough, or with enough frames to keep up. 173 // An underrun event is counted, and the caller should re-try this operation. 174 virtual ssize_t write(const void *buffer, size_t count) = 0; 175 176 // Transfer data to sink using a series of callbacks. More suitable for zero-fill, synthesis, 177 // and non-contiguous transfers (e.g. circular buffer or writev). 178 // Inputs: 179 // via Callback function that the sink will call as many times as needed to consume data. 180 // total Estimate of the number of frames the provider has available. This is an estimate, 181 // and it can provide a different number of frames during the series of callbacks. 182 // user Arbitrary void * reserved for data provider. 183 // block Number of frames per block, that is a suggested value for 'count' in each callback. 184 // Zero means no preference. This parameter is a hint only, and may be ignored. 185 // Return value: 186 // > 0 Total number of frames successfully transferred prior to first error. 187 // = 0 Count was zero. 188 // < 0 status_t error occurred prior to the first frame transfer. 189 // Errors: 190 // NEGOTIATE (Re-)negotiation is needed. 191 // WOULD_BLOCK No frames can be transferred without blocking. 192 // UNDERRUN write() has not been called frequently enough, or with enough frames to keep up. 193 // An underrun event is counted, and the caller should re-try this operation. 194 // 195 // The 'via' callback is called by the data sink as follows: 196 // Inputs: 197 // user Arbitrary void * reserved for data provider. 198 // buffer Non-NULL buffer owned by sink that callback should fill in with data, 199 // up to a maximum of 'count' frames. 200 // count Maximum number of frames to transfer during this callback. 201 // Return value: 202 // > 0 Number of frames successfully transferred during this callback prior to first error. 203 // = 0 Count was zero. 204 // < 0 status_t error occurred prior to the first frame transfer during this callback. 205 virtual ssize_t writeVia(writeVia_t via, size_t total, void *user, size_t block = 0); 206 207 // Get the time (on the LocalTime timeline) at which the first frame of audio of the next write 208 // operation to this sink will be eventually rendered by the HAL. 209 // Inputs: 210 // ts A pointer pointing to the int64_t which will hold the result. 211 // Return value: 212 // OK Everything went well, *ts holds the time at which the first audio frame of the next 213 // write operation will be rendered, or AudioBufferProvider::kInvalidPTS if this sink 214 // does not know the answer for some reason. Sinks which eventually lead to a HAL 215 // which implements get_next_write_timestamp may return Invalid temporarily if the DMA 216 // output of the audio driver has not started yet. Sinks which lead to a HAL which 217 // does not implement get_next_write_timestamp, or which don't lead to a HAL at all, 218 // will always return kInvalidPTS. 219 // <other> Something unexpected happened internally. Check the logs and start debugging. 220 virtual status_t getNextWriteTimestamp(int64_t *ts) { return INVALID_OPERATION; } 221 222 // Returns NO_ERROR if a timestamp is available. The timestamp includes the total number 223 // of frames presented to an external observer, together with the value of CLOCK_MONOTONIC 224 // as of this presentation count. 225 virtual status_t getTimestamp(AudioTimestamp& timestamp) { return INVALID_OPERATION; } 226 227protected: 228 NBAIO_Sink(const NBAIO_Format& format = Format_Invalid) : NBAIO_Port(format), mFramesWritten(0) { } 229 virtual ~NBAIO_Sink() { } 230 231 // Implementations are free to ignore these if they don't need them 232 size_t mFramesWritten; 233}; 234 235// Abstract class (interface) representing a non-blocking data source, for use by a data consumer. 236class NBAIO_Source : public NBAIO_Port { 237 238public: 239 240 // For the next two APIs: 241 // 32 bits rolls over after 27 hours at 44.1 kHz; if that concerns you then poll periodically. 242 243 // Number of frames read successfully since construction. 244 virtual size_t framesRead() const { return mFramesRead; } 245 246 // Number of frames lost due to overrun since construction. 247 // Not const because implementations may need to do I/O. 248 virtual size_t framesOverrun() /*const*/ { return 0; } 249 250 // Number of overruns since construction, where a set of contiguous lost frames is one event. 251 // Not const because implementations may need to do I/O. 252 virtual size_t overruns() /*const*/ { return 0; } 253 254 // Estimate of number of frames that could be read successfully now. 255 // When a read() is actually attempted, the implementation is permitted to return a smaller or 256 // larger transfer count, however it will make a good faith effort to give an accurate estimate. 257 // Errors: 258 // NEGOTIATE (Re-)negotiation is needed. 259 // OVERRUN One or more frames were lost due to overrun, try again to read more recent data. 260 // WOULD_BLOCK Determining how many frames can be read without blocking would itself block. 261 virtual ssize_t availableToRead() { return SSIZE_MAX; } 262 263 // Transfer data from source into single destination buffer. Implies a copy. 264 // Inputs: 265 // buffer Non-NULL destination buffer owned by consumer. 266 // count Maximum number of frames to transfer. 267 // readPTS The presentation time (on the LocalTime timeline) for which data 268 // is being requested, or kInvalidPTS if not known. 269 // Return value: 270 // > 0 Number of frames successfully transferred prior to first error. 271 // = 0 Count was zero. 272 // < 0 status_t error occurred prior to the first frame transfer. 273 // Errors: 274 // NEGOTIATE (Re-)negotiation is needed. 275 // WOULD_BLOCK No frames can be transferred without blocking. 276 // OVERRUN read() has not been called frequently enough, or with enough frames to keep up. 277 // One or more frames were lost due to overrun, try again to read more recent data. 278 virtual ssize_t read(void *buffer, size_t count, int64_t readPTS) = 0; 279 280 // Transfer data from source using a series of callbacks. More suitable for zero-fill, 281 // synthesis, and non-contiguous transfers (e.g. circular buffer or readv). 282 // Inputs: 283 // via Callback function that the source will call as many times as needed to provide data. 284 // total Estimate of the number of frames the consumer desires. This is an estimate, 285 // and it can consume a different number of frames during the series of callbacks. 286 // user Arbitrary void * reserved for data consumer. 287 // readPTS The presentation time (on the LocalTime timeline) for which data 288 // is being requested, or kInvalidPTS if not known. 289 // block Number of frames per block, that is a suggested value for 'count' in each callback. 290 // Zero means no preference. This parameter is a hint only, and may be ignored. 291 // Return value: 292 // > 0 Total number of frames successfully transferred prior to first error. 293 // = 0 Count was zero. 294 // < 0 status_t error occurred prior to the first frame transfer. 295 // Errors: 296 // NEGOTIATE (Re-)negotiation is needed. 297 // WOULD_BLOCK No frames can be transferred without blocking. 298 // OVERRUN read() has not been called frequently enough, or with enough frames to keep up. 299 // One or more frames were lost due to overrun, try again to read more recent data. 300 // 301 // The 'via' callback is called by the data source as follows: 302 // Inputs: 303 // user Arbitrary void * reserved for data consumer. 304 // dest Non-NULL buffer owned by source that callback should consume data from, 305 // up to a maximum of 'count' frames. 306 // count Maximum number of frames to transfer during this callback. 307 // Return value: 308 // > 0 Number of frames successfully transferred during this callback prior to first error. 309 // = 0 Count was zero. 310 // < 0 status_t error occurred prior to the first frame transfer during this callback. 311 virtual ssize_t readVia(readVia_t via, size_t total, void *user, 312 int64_t readPTS, size_t block = 0); 313 314 // Invoked asynchronously by corresponding sink when a new timestamp is available. 315 // Default implementation ignores the timestamp. 316 virtual void onTimestamp(const AudioTimestamp& timestamp) { } 317 318protected: 319 NBAIO_Source(const NBAIO_Format& format = Format_Invalid) : NBAIO_Port(format), mFramesRead(0) { } 320 virtual ~NBAIO_Source() { } 321 322 // Implementations are free to ignore these if they don't need them 323 size_t mFramesRead; 324}; 325 326} // namespace android 327 328#endif // ANDROID_AUDIO_NBAIO_H 329