/* * Copyright (C) 2012 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_NBAIO_H #define ANDROID_AUDIO_NBAIO_H // Non-blocking audio I/O interface // // This header file has the abstract interfaces only. Concrete implementation classes are declared // elsewhere. Implementations _should_ be non-blocking for all methods, especially read() and // write(), but this is not enforced. In general, implementations do not need to be multi-thread // safe, and any exceptions are noted in the particular implementation. #include #include #include #include #include #include namespace android { // In addition to the usual status_t enum { NEGOTIATE = 0x80000010, // Must (re-)negotiate format. For negotiate() only, the offeree // doesn't accept offers, and proposes counter-offers OVERRUN = 0x80000011, // availableToRead(), read(), or readVia() detected lost input due // to overrun; an event is counted and the caller should re-try UNDERRUN = 0x80000012, // availableToWrite(), write(), or writeVia() detected a gap in // output due to underrun (not being called often enough, or with // enough data); an event is counted and the caller should re-try }; // Negotiation of format is based on the data provider and data sink, or the data consumer and // data source, exchanging prioritized arrays of offers and counter-offers until a single offer is // mutually agreed upon. Each offer is an NBAIO_Format. For simplicity and performance, // NBAIO_Format is a typedef that ties together the most important combinations of the various // attributes, rather than a struct with separate fields for format, sample rate, channel count, // interleave, packing, alignment, etc. The reason is that NBAIO_Format tries to abstract out only // the combinations that are actually needed within AudioFlinger. If the list of combinations grows // too large, then this decision should be re-visited. // Sample rate and channel count are explicit, PCM interleaved 16-bit is assumed. struct NBAIO_Format { // FIXME make this a class, and change Format_... global methods to class methods //private: unsigned mSampleRate; unsigned mChannelCount; audio_format_t mFormat; size_t mFrameSize; }; extern const NBAIO_Format Format_Invalid; // Return the frame size of an NBAIO_Format in bytes size_t Format_frameSize(const NBAIO_Format& format); // Convert a sample rate in Hz and channel count to an NBAIO_Format // FIXME rename NBAIO_Format Format_from_SR_C(unsigned sampleRate, unsigned channelCount, audio_format_t format); // Return the sample rate in Hz of an NBAIO_Format unsigned Format_sampleRate(const NBAIO_Format& format); // Return the channel count of an NBAIO_Format unsigned Format_channelCount(const NBAIO_Format& format); // Callbacks used by NBAIO_Sink::writeVia() and NBAIO_Source::readVia() below. typedef ssize_t (*writeVia_t)(void *user, void *buffer, size_t count); typedef ssize_t (*readVia_t)(void *user, const void *buffer, size_t count, int64_t readPTS); // Check whether an NBAIO_Format is valid bool Format_isValid(const NBAIO_Format& format); // Compare two NBAIO_Format values bool Format_isEqual(const NBAIO_Format& format1, const NBAIO_Format& format2); // Abstract class (interface) representing a data port. class NBAIO_Port : public RefBase { public: // negotiate() must called first. The purpose of negotiate() is to check compatibility of // formats, not to automatically adapt if they are incompatible. It's the responsibility of // whoever sets up the graph connections to make sure formats are compatible, and this method // just verifies that. The edges are "dumb" and don't attempt to adapt to bad connections. // How it works: offerer proposes an array of formats, in descending order of preference from // offers[0] to offers[numOffers - 1]. If offeree accepts one of these formats, it returns // the index of that offer. Otherwise, offeree sets numCounterOffers to the number of // counter-offers (up to a maximumum of the entry value of numCounterOffers), fills in the // provided array counterOffers[] with its counter-offers, in descending order of preference // from counterOffers[0] to counterOffers[numCounterOffers - 1], and returns NEGOTIATE. // Note that since the offerer allocates space for counter-offers, but only the offeree knows // how many counter-offers it has, there may be insufficient space for all counter-offers. // In that case, the offeree sets numCounterOffers to the requested number of counter-offers // (which is greater than the entry value of numCounterOffers), fills in as many of the most // important counterOffers as will fit, and returns NEGOTIATE. As this implies a re-allocation, // it should be used as a last resort. It is preferable for the offerer to simply allocate a // larger space to begin with, and/or for the offeree to tolerate a smaller space than desired. // Alternatively, the offerer can pass NULL for offers and counterOffers, and zero for // numOffers. This indicates that it has not allocated space for any counter-offers yet. // In this case, the offerree should set numCounterOffers appropriately and return NEGOTIATE. // Then the offerer will allocate the correct amount of memory and retry. // Format_Invalid is not allowed as either an offer or counter-offer. // Returns: // >= 0 Offer accepted. // NEGOTIATE No offer accepted, and counter-offer(s) optionally made. See above for details. virtual ssize_t negotiate(const NBAIO_Format offers[], size_t numOffers, NBAIO_Format counterOffers[], size_t& numCounterOffers); // Return the current negotiated format, or Format_Invalid if negotiation has not been done, // or if re-negotiation is required. virtual NBAIO_Format format() const { return mNegotiated ? mFormat : Format_Invalid; } protected: NBAIO_Port(const NBAIO_Format& format) : mNegotiated(false), mFormat(format), mFrameSize(Format_frameSize(format)) { } virtual ~NBAIO_Port() { } // Implementations are free to ignore these if they don't need them bool mNegotiated; // mNegotiated implies (mFormat != Format_Invalid) NBAIO_Format mFormat; // (mFormat != Format_Invalid) does not imply mNegotiated size_t mFrameSize; // assign in parallel with any assignment to mFormat }; // Abstract class (interface) representing a non-blocking data sink, for use by a data provider. class NBAIO_Sink : public NBAIO_Port { public: // For the next two APIs: // 32 bits rolls over after 27 hours at 44.1 kHz; if that concerns you then poll periodically. // Return the number of frames written successfully since construction. virtual size_t framesWritten() const { return mFramesWritten; } // Number of frames lost due to underrun since construction. virtual size_t framesUnderrun() const { return 0; } // Number of underruns since construction, where a set of contiguous lost frames is one event. virtual size_t underruns() const { return 0; } // Estimate of number of frames that could be written successfully now without blocking. // When a write() is actually attempted, the implementation is permitted to return a smaller or // larger transfer count, however it will make a good faith effort to give an accurate estimate. // Errors: // NEGOTIATE (Re-)negotiation is needed. // UNDERRUN write() has not been called frequently enough, or with enough frames to keep up. // An underrun event is counted, and the caller should re-try this operation. // WOULD_BLOCK Determining how many frames can be written without blocking would itself block. virtual ssize_t availableToWrite() const { return SSIZE_MAX; } // Transfer data to sink from single input buffer. Implies a copy. // Inputs: // buffer Non-NULL buffer owned by provider. // count Maximum number of frames to transfer. // Return value: // > 0 Number of frames successfully transferred prior to first error. // = 0 Count was zero. // < 0 status_t error occurred prior to the first frame transfer. // Errors: // NEGOTIATE (Re-)negotiation is needed. // WOULD_BLOCK No frames can be transferred without blocking. // UNDERRUN write() has not been called frequently enough, or with enough frames to keep up. // An underrun event is counted, and the caller should re-try this operation. virtual ssize_t write(const void *buffer, size_t count) = 0; // Transfer data to sink using a series of callbacks. More suitable for zero-fill, synthesis, // and non-contiguous transfers (e.g. circular buffer or writev). // Inputs: // via Callback function that the sink will call as many times as needed to consume data. // total Estimate of the number of frames the provider has available. This is an estimate, // and it can provide a different number of frames during the series of callbacks. // user Arbitrary void * reserved for data provider. // block Number of frames per block, that is a suggested value for 'count' in each callback. // Zero means no preference. This parameter is a hint only, and may be ignored. // Return value: // > 0 Total number of frames successfully transferred prior to first error. // = 0 Count was zero. // < 0 status_t error occurred prior to the first frame transfer. // Errors: // NEGOTIATE (Re-)negotiation is needed. // WOULD_BLOCK No frames can be transferred without blocking. // UNDERRUN write() has not been called frequently enough, or with enough frames to keep up. // An underrun event is counted, and the caller should re-try this operation. // // The 'via' callback is called by the data sink as follows: // Inputs: // user Arbitrary void * reserved for data provider. // buffer Non-NULL buffer owned by sink that callback should fill in with data, // up to a maximum of 'count' frames. // count Maximum number of frames to transfer during this callback. // Return value: // > 0 Number of frames successfully transferred during this callback prior to first error. // = 0 Count was zero. // < 0 status_t error occurred prior to the first frame transfer during this callback. virtual ssize_t writeVia(writeVia_t via, size_t total, void *user, size_t block = 0); // Get the time (on the LocalTime timeline) at which the first frame of audio of the next write // operation to this sink will be eventually rendered by the HAL. // Inputs: // ts A pointer pointing to the int64_t which will hold the result. // Return value: // OK Everything went well, *ts holds the time at which the first audio frame of the next // write operation will be rendered, or AudioBufferProvider::kInvalidPTS if this sink // does not know the answer for some reason. Sinks which eventually lead to a HAL // which implements get_next_write_timestamp may return Invalid temporarily if the DMA // output of the audio driver has not started yet. Sinks which lead to a HAL which // does not implement get_next_write_timestamp, or which don't lead to a HAL at all, // will always return kInvalidPTS. // Something unexpected happened internally. Check the logs and start debugging. virtual status_t getNextWriteTimestamp(int64_t *ts) { return INVALID_OPERATION; } // Returns NO_ERROR if a timestamp is available. The timestamp includes the total number // of frames presented to an external observer, together with the value of CLOCK_MONOTONIC // as of this presentation count. The timestamp parameter is undefined if error is returned. virtual status_t getTimestamp(AudioTimestamp& timestamp) { return INVALID_OPERATION; } protected: NBAIO_Sink(const NBAIO_Format& format = Format_Invalid) : NBAIO_Port(format), mFramesWritten(0) { } virtual ~NBAIO_Sink() { } // Implementations are free to ignore these if they don't need them size_t mFramesWritten; }; // Abstract class (interface) representing a non-blocking data source, for use by a data consumer. class NBAIO_Source : public NBAIO_Port { public: // For the next two APIs: // 32 bits rolls over after 27 hours at 44.1 kHz; if that concerns you then poll periodically. // Number of frames read successfully since construction. virtual size_t framesRead() const { return mFramesRead; } // Number of frames lost due to overrun since construction. // Not const because implementations may need to do I/O. virtual size_t framesOverrun() /*const*/ { return 0; } // Number of overruns since construction, where a set of contiguous lost frames is one event. // Not const because implementations may need to do I/O. virtual size_t overruns() /*const*/ { return 0; } // Estimate of number of frames that could be read successfully now. // When a read() is actually attempted, the implementation is permitted to return a smaller or // larger transfer count, however it will make a good faith effort to give an accurate estimate. // Errors: // NEGOTIATE (Re-)negotiation is needed. // OVERRUN One or more frames were lost due to overrun, try again to read more recent data. // WOULD_BLOCK Determining how many frames can be read without blocking would itself block. virtual ssize_t availableToRead() { return SSIZE_MAX; } // Transfer data from source into single destination buffer. Implies a copy. // Inputs: // buffer Non-NULL destination buffer owned by consumer. // count Maximum number of frames to transfer. // readPTS The presentation time (on the LocalTime timeline) for which data // is being requested, or kInvalidPTS if not known. // Return value: // > 0 Number of frames successfully transferred prior to first error. // = 0 Count was zero. // < 0 status_t error occurred prior to the first frame transfer. // Errors: // NEGOTIATE (Re-)negotiation is needed. // WOULD_BLOCK No frames can be transferred without blocking. // OVERRUN read() has not been called frequently enough, or with enough frames to keep up. // One or more frames were lost due to overrun, try again to read more recent data. virtual ssize_t read(void *buffer, size_t count, int64_t readPTS) = 0; // Transfer data from source using a series of callbacks. More suitable for zero-fill, // synthesis, and non-contiguous transfers (e.g. circular buffer or readv). // Inputs: // via Callback function that the source will call as many times as needed to provide data. // total Estimate of the number of frames the consumer desires. This is an estimate, // and it can consume a different number of frames during the series of callbacks. // user Arbitrary void * reserved for data consumer. // readPTS The presentation time (on the LocalTime timeline) for which data // is being requested, or kInvalidPTS if not known. // block Number of frames per block, that is a suggested value for 'count' in each callback. // Zero means no preference. This parameter is a hint only, and may be ignored. // Return value: // > 0 Total number of frames successfully transferred prior to first error. // = 0 Count was zero. // < 0 status_t error occurred prior to the first frame transfer. // Errors: // NEGOTIATE (Re-)negotiation is needed. // WOULD_BLOCK No frames can be transferred without blocking. // OVERRUN read() has not been called frequently enough, or with enough frames to keep up. // One or more frames were lost due to overrun, try again to read more recent data. // // The 'via' callback is called by the data source as follows: // Inputs: // user Arbitrary void * reserved for data consumer. // dest Non-NULL buffer owned by source that callback should consume data from, // up to a maximum of 'count' frames. // count Maximum number of frames to transfer during this callback. // Return value: // > 0 Number of frames successfully transferred during this callback prior to first error. // = 0 Count was zero. // < 0 status_t error occurred prior to the first frame transfer during this callback. virtual ssize_t readVia(readVia_t via, size_t total, void *user, int64_t readPTS, size_t block = 0); // Invoked asynchronously by corresponding sink when a new timestamp is available. // Default implementation ignores the timestamp. virtual void onTimestamp(const AudioTimestamp& timestamp) { } protected: NBAIO_Source(const NBAIO_Format& format = Format_Invalid) : NBAIO_Port(format), mFramesRead(0) { } virtual ~NBAIO_Source() { } // Implementations are free to ignore these if they don't need them size_t mFramesRead; }; } // namespace android #endif // ANDROID_AUDIO_NBAIO_H