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Diffstat (limited to 'include/media/nbaio/NBAIO.h')
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diff --git a/include/media/nbaio/NBAIO.h b/include/media/nbaio/NBAIO.h new file mode 100644 index 0000000..81f42ed --- /dev/null +++ b/include/media/nbaio/NBAIO.h @@ -0,0 +1,315 @@ +/* + * 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 <limits.h> +#include <stdlib.h> +#include <utils/Errors.h> +#include <utils/RefBase.h> + +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 an enum 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 AudioFligner. If the list of combinations grows +// too large, then this decision should be re-visited. +enum NBAIO_Format { + Format_Invalid, + Format_SR44_1_C2_I16, // 44.1 kHz PCM stereo interleaved 16-bit signed + Format_SR48_C2_I16, // 48 kHz PCM stereo interleaved 16-bit signed + Format_SR44_1_C1_I16, // 44.1 kHz PCM mono interleaved 16-bit signed + Format_SR48_C1_I16, // 48 kHz PCM mono interleaved 16-bit signed +}; + +// Return the frame size of an NBAIO_Format in bytes +size_t Format_frameSize(NBAIO_Format format); + +// Return the frame size of an NBAIO_Format as a bit shift +size_t Format_frameBitShift(NBAIO_Format format); + +// Convert a sample rate in Hz and channel count to an NBAIO_Format +NBAIO_Format Format_from_SR_C(unsigned sampleRate, unsigned channelCount); + +// Return the sample rate in Hz of an NBAIO_Format +unsigned Format_sampleRate(NBAIO_Format format); + +// Return the channel count of an NBAIO_Format +unsigned Format_channelCount(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); + +// 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(NBAIO_Format format) : mNegotiated(false), mFormat(format), + mBitShift(Format_frameBitShift(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 mBitShift; // 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. + // <other> Something unexpected happened internally. Check the logs and start debugging. + virtual status_t getNextWriteTimestamp(int64_t *ts) { return INVALID_OPERATION; } + +protected: + NBAIO_Sink(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); + +protected: + NBAIO_Source(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 |