FastMixer.cpp revision 97b5d0d5b5ef766eb5dd680d05a5d199662d4ae0 
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#define LOG_TAG "FastMixer"
18//#define LOG_NDEBUG 0
19
20#include <sys/atomics.h>
21#include <time.h>
22#include <utils/Log.h>
23#include <system/audio.h>
24#ifdef FAST_MIXER_STATISTICS
25#include <cpustats/CentralTendencyStatistics.h>
26#endif
27#include "AudioMixer.h"
28#include "FastMixer.h"
29
30#define FAST_HOT_IDLE_NS     1000000L   // 1 ms: time to sleep while hot idling
31#define FAST_DEFAULT_NS    999999999L   // ~1 sec: default time to sleep
32
33namespace android {
34
35// Fast mixer thread
36bool FastMixer::threadLoop()
37{
38    static const FastMixerState initial;
39    const FastMixerState *previous = &initial, *current = &initial;
40    FastMixerState preIdle; // copy of state before we went into idle
41    struct timespec oldTs = {0, 0};
42    bool oldTsValid = false;
43    long slopNs = 0;    // accumulated time we've woken up too early (> 0) or too late (< 0)
44    long sleepNs = -1;  // -1: busy wait, 0: sched_yield, > 0: nanosleep
45    int fastTrackNames[FastMixerState::kMaxFastTracks]; // handles used by mixer to identify tracks
46    int generations[FastMixerState::kMaxFastTracks];    // last observed mFastTracks[i].mGeneration
47    unsigned i;
48    for (i = 0; i < FastMixerState::kMaxFastTracks; ++i) {
49        fastTrackNames[i] = -1;
50        generations[i] = 0;
51    }
52    NBAIO_Sink *outputSink = NULL;
53    int outputSinkGen = 0;
54    AudioMixer* mixer = NULL;
55    short *mixBuffer = NULL;
56    enum {UNDEFINED, MIXED, ZEROED} mixBufferState = UNDEFINED;
57    NBAIO_Format format = Format_Invalid;
58    unsigned sampleRate = 0;
59    int fastTracksGen = 0;
60    long periodNs = 0;      // expected period; the time required to render one mix buffer
61    long underrunNs = 0;    // an underrun is likely if an actual cycle is greater than this value
62    long overrunNs = 0;     // an overrun is likely if an actual cycle if less than this value
63    FastMixerDumpState dummyDumpState, *dumpState = &dummyDumpState;
64    bool ignoreNextOverrun = true;  // used to ignore initial overrun and first after an underrun
65#ifdef FAST_MIXER_STATISTICS
66    CentralTendencyStatistics cts;  // cycle times in seconds
67    static const unsigned kMaxSamples = 1000;
68#endif
69    unsigned coldGen = 0;   // last observed mColdGen
70
71    for (;;) {
72
73        // either nanosleep, sched_yield, or busy wait
74        if (sleepNs >= 0) {
75            if (sleepNs > 0) {
76                ALOG_ASSERT(sleepNs < 1000000000);
77                const struct timespec req = {0, sleepNs};
78                nanosleep(&req, NULL);
79            } else {
80                sched_yield();
81            }
82        }
83        // default to long sleep for next cycle
84        sleepNs = FAST_DEFAULT_NS;
85
86        // poll for state change
87        const FastMixerState *next = mSQ.poll();
88        if (next == NULL) {
89            // continue to use the default initial state until a real state is available
90            ALOG_ASSERT(current == &initial && previous == &initial);
91            next = current;
92        }
93
94        FastMixerState::Command command = next->mCommand;
95        if (next != current) {
96
97            // As soon as possible of learning of a new dump area, start using it
98            dumpState = next->mDumpState != NULL ? next->mDumpState : &dummyDumpState;
99
100            // We want to always have a valid reference to the previous (non-idle) state.
101            // However, the state queue only guarantees access to current and previous states.
102            // So when there is a transition from a non-idle state into an idle state, we make a
103            // copy of the last known non-idle state so it is still available on return from idle.
104            // The possible transitions are:
105            //  non-idle -> non-idle    update previous from current in-place
106            //  non-idle -> idle        update previous from copy of current
107            //  idle     -> idle        don't update previous
108            //  idle     -> non-idle    don't update previous
109            if (!(current->mCommand & FastMixerState::IDLE)) {
110                if (command & FastMixerState::IDLE) {
111                    preIdle = *current;
112                    current = &preIdle;
113                    oldTsValid = false;
114                    ignoreNextOverrun = true;
115                }
116                previous = current;
117            }
118            current = next;
119        }
120#if !LOG_NDEBUG
121        next = NULL;    // not referenced again
122#endif
123
124        dumpState->mCommand = command;
125
126        switch (command) {
127        case FastMixerState::INITIAL:
128        case FastMixerState::HOT_IDLE:
129            sleepNs = FAST_HOT_IDLE_NS;
130            continue;
131        case FastMixerState::COLD_IDLE:
132            // only perform a cold idle command once
133            if (current->mColdGen != coldGen) {
134                int32_t *coldFutexAddr = current->mColdFutexAddr;
135                ALOG_ASSERT(coldFutexAddr != NULL);
136                int32_t old = android_atomic_dec(coldFutexAddr);
137                if (old <= 0) {
138                    __futex_syscall4(coldFutexAddr, FUTEX_WAIT_PRIVATE, old - 1, NULL);
139                }
140                sleepNs = -1;
141                coldGen = current->mColdGen;
142            } else {
143                sleepNs = FAST_HOT_IDLE_NS;
144            }
145            continue;
146        case FastMixerState::EXIT:
147            delete mixer;
148            delete[] mixBuffer;
149            return false;
150        case FastMixerState::MIX:
151        case FastMixerState::WRITE:
152        case FastMixerState::MIX_WRITE:
153            break;
154        default:
155            LOG_FATAL("bad command %d", command);
156        }
157
158        // there is a non-idle state available to us; did the state change?
159        size_t frameCount = current->mFrameCount;
160        if (current != previous) {
161
162            // handle state change here, but since we want to diff the state,
163            // we're prepared for previous == &initial the first time through
164            unsigned previousTrackMask;
165
166            // check for change in output HAL configuration
167            NBAIO_Format previousFormat = format;
168            if (current->mOutputSinkGen != outputSinkGen) {
169                outputSink = current->mOutputSink;
170                outputSinkGen = current->mOutputSinkGen;
171                if (outputSink == NULL) {
172                    format = Format_Invalid;
173                    sampleRate = 0;
174                } else {
175                    format = outputSink->format();
176                    sampleRate = Format_sampleRate(format);
177                    ALOG_ASSERT(Format_channelCount(format) == 2);
178                }
179            }
180
181            if ((format != previousFormat) || (frameCount != previous->mFrameCount)) {
182                // FIXME to avoid priority inversion, don't delete here
183                delete mixer;
184                mixer = NULL;
185                delete[] mixBuffer;
186                mixBuffer = NULL;
187                if (frameCount > 0 && sampleRate > 0) {
188                    // FIXME new may block for unbounded time at internal mutex of the heap
189                    //       implementation; it would be better to have normal mixer allocate for us
190                    //       to avoid blocking here and to prevent possible priority inversion
191                    mixer = new AudioMixer(frameCount, sampleRate, FastMixerState::kMaxFastTracks);
192                    mixBuffer = new short[frameCount * 2];
193                    periodNs = (frameCount * 1000000000LL) / sampleRate;    // 1.00
194                    underrunNs = (frameCount * 1750000000LL) / sampleRate;  // 1.75
195                    overrunNs = (frameCount * 250000000LL) / sampleRate;    // 0.25
196                } else {
197                    periodNs = 0;
198                    underrunNs = 0;
199                    overrunNs = 0;
200                }
201                mixBufferState = UNDEFINED;
202#if !LOG_NDEBUG
203                for (i = 0; i < FastMixerState::kMaxFastTracks; ++i) {
204                    fastTrackNames[i] = -1;
205                }
206#endif
207                // we need to reconfigure all active tracks
208                previousTrackMask = 0;
209                fastTracksGen = current->mFastTracksGen - 1;
210            } else {
211                previousTrackMask = previous->mTrackMask;
212            }
213
214            // check for change in active track set
215            unsigned currentTrackMask = current->mTrackMask;
216            if (current->mFastTracksGen != fastTracksGen) {
217                ALOG_ASSERT(mixBuffer != NULL);
218                int name;
219
220                // process removed tracks first to avoid running out of track names
221                unsigned removedTracks = previousTrackMask & ~currentTrackMask;
222                while (removedTracks != 0) {
223                    i = __builtin_ctz(removedTracks);
224                    removedTracks &= ~(1 << i);
225                    const FastTrack* fastTrack = &current->mFastTracks[i];
226                    if (mixer != NULL) {
227                        name = fastTrackNames[i];
228                        ALOG_ASSERT(name >= 0);
229                        mixer->deleteTrackName(name);
230                    }
231#if !LOG_NDEBUG
232                    fastTrackNames[i] = -1;
233#endif
234                    generations[i] = fastTrack->mGeneration;
235                }
236
237                // now process added tracks
238                unsigned addedTracks = currentTrackMask & ~previousTrackMask;
239                while (addedTracks != 0) {
240                    i = __builtin_ctz(addedTracks);
241                    addedTracks &= ~(1 << i);
242                    const FastTrack* fastTrack = &current->mFastTracks[i];
243                    AudioBufferProvider *bufferProvider = fastTrack->mBufferProvider;
244                    ALOG_ASSERT(bufferProvider != NULL && fastTrackNames[i] == -1);
245                    if (mixer != NULL) {
246                        name = mixer->getTrackName();
247                        ALOG_ASSERT(name >= 0);
248                        fastTrackNames[i] = name;
249                        mixer->setBufferProvider(name, bufferProvider);
250                        mixer->setParameter(name, AudioMixer::TRACK, AudioMixer::MAIN_BUFFER,
251                                (void *) mixBuffer);
252                        // newly allocated track names default to full scale volume
253                        mixer->enable(name);
254                    }
255                    generations[i] = fastTrack->mGeneration;
256                }
257
258                // finally process modified tracks; these use the same slot
259                // but may have a different buffer provider or volume provider
260                unsigned modifiedTracks = currentTrackMask & previousTrackMask;
261                while (modifiedTracks != 0) {
262                    i = __builtin_ctz(modifiedTracks);
263                    modifiedTracks &= ~(1 << i);
264                    const FastTrack* fastTrack = &current->mFastTracks[i];
265                    if (fastTrack->mGeneration != generations[i]) {
266                        AudioBufferProvider *bufferProvider = fastTrack->mBufferProvider;
267                        ALOG_ASSERT(bufferProvider != NULL);
268                        if (mixer != NULL) {
269                            name = fastTrackNames[i];
270                            ALOG_ASSERT(name >= 0);
271                            mixer->setBufferProvider(name, bufferProvider);
272                            if (fastTrack->mVolumeProvider == NULL) {
273                                mixer->setParameter(name, AudioMixer::VOLUME, AudioMixer::VOLUME0,
274                                        (void *)0x1000);
275                                mixer->setParameter(name, AudioMixer::VOLUME, AudioMixer::VOLUME1,
276                                        (void *)0x1000);
277                            }
278                            // already enabled
279                        }
280                        generations[i] = fastTrack->mGeneration;
281                    }
282                }
283
284                fastTracksGen = current->mFastTracksGen;
285
286                dumpState->mNumTracks = popcount(currentTrackMask);
287            }
288
289#if 1   // FIXME shouldn't need this
290            // only process state change once
291            previous = current;
292#endif
293        }
294
295        // do work using current state here
296        if ((command & FastMixerState::MIX) && (mixer != NULL)) {
297            ALOG_ASSERT(mixBuffer != NULL);
298            // update volumes
299            unsigned volumeTracks = current->mTrackMask;
300            while (volumeTracks != 0) {
301                i = __builtin_ctz(volumeTracks);
302                volumeTracks &= ~(1 << i);
303                const FastTrack* fastTrack = &current->mFastTracks[i];
304                int name = fastTrackNames[i];
305                ALOG_ASSERT(name >= 0);
306                if (fastTrack->mVolumeProvider != NULL) {
307                    uint32_t vlr = fastTrack->mVolumeProvider->getVolumeLR();
308                    mixer->setParameter(name, AudioMixer::VOLUME, AudioMixer::VOLUME0,
309                            (void *)(vlr & 0xFFFF));
310                    mixer->setParameter(name, AudioMixer::VOLUME, AudioMixer::VOLUME1,
311                            (void *)(vlr >> 16));
312                }
313            }
314            // process() is CPU-bound
315            mixer->process(AudioBufferProvider::kInvalidPTS);
316            mixBufferState = MIXED;
317        } else if (mixBufferState == MIXED) {
318            mixBufferState = UNDEFINED;
319        }
320        if ((command & FastMixerState::WRITE) && (outputSink != NULL) && (mixBuffer != NULL)) {
321            if (mixBufferState == UNDEFINED) {
322                memset(mixBuffer, 0, frameCount * 2 * sizeof(short));
323                mixBufferState = ZEROED;
324            }
325            // FIXME write() is non-blocking and lock-free for a properly implemented NBAIO sink,
326            //       but this code should be modified to handle both non-blocking and blocking sinks
327            dumpState->mWriteSequence++;
328            ssize_t framesWritten = outputSink->write(mixBuffer, frameCount);
329            dumpState->mWriteSequence++;
330            if (framesWritten >= 0) {
331                dumpState->mFramesWritten += framesWritten;
332            } else {
333                dumpState->mWriteErrors++;
334            }
335            // FIXME count # of writes blocked excessively, CPU usage, etc. for dump
336        }
337
338        // To be exactly periodic, compute the next sleep time based on current time.
339        // This code doesn't have long-term stability when the sink is non-blocking.
340        // FIXME To avoid drift, use the local audio clock or watch the sink's fill status.
341        struct timespec newTs;
342        int rc = clock_gettime(CLOCK_MONOTONIC, &newTs);
343        if (rc == 0) {
344            if (oldTsValid) {
345                time_t sec = newTs.tv_sec - oldTs.tv_sec;
346                long nsec = newTs.tv_nsec - oldTs.tv_nsec;
347                if (nsec < 0) {
348                    --sec;
349                    nsec += 1000000000;
350                }
351                if (sec > 0 || nsec > underrunNs) {
352                    // FIXME only log occasionally
353                    ALOGV("underrun: time since last cycle %d.%03ld sec",
354                            (int) sec, nsec / 1000000L);
355                    dumpState->mUnderruns++;
356                    sleepNs = -1;
357                    ignoreNextOverrun = true;
358                } else if (nsec < overrunNs) {
359                    if (ignoreNextOverrun) {
360                        ignoreNextOverrun = false;
361                    } else {
362                        // FIXME only log occasionally
363                        ALOGV("overrun: time since last cycle %d.%03ld sec",
364                                (int) sec, nsec / 1000000L);
365                        dumpState->mOverruns++;
366                    }
367                    sleepNs = periodNs - overrunNs;
368                } else {
369                    sleepNs = -1;
370                    ignoreNextOverrun = false;
371                }
372#ifdef FAST_MIXER_STATISTICS
373                // long-term statistics
374                cts.sample(sec + nsec * 1e-9);
375                if (cts.n() >= kMaxSamples) {
376                    dumpState->mMean = cts.mean();
377                    dumpState->mMinimum = cts.minimum();
378                    dumpState->mMaximum = cts.maximum();
379                    dumpState->mStddev = cts.stddev();
380                    cts.reset();
381                }
382#endif
383            } else {
384                // first time through the loop
385                oldTsValid = true;
386                sleepNs = periodNs;
387                ignoreNextOverrun = true;
388            }
389            oldTs = newTs;
390        } else {
391            // monotonic clock is broken
392            oldTsValid = false;
393            sleepNs = periodNs;
394        }
395
396    }   // for (;;)
397
398    // never return 'true'; Thread::_threadLoop() locks mutex which can result in priority inversion
399}
400
401FastMixerDumpState::FastMixerDumpState() :
402    mCommand(FastMixerState::INITIAL), mWriteSequence(0), mFramesWritten(0),
403    mNumTracks(0), mWriteErrors(0), mUnderruns(0), mOverruns(0)
404#ifdef FAST_MIXER_STATISTICS
405    , mMean(0.0), mMinimum(0.0), mMaximum(0.0), mStddev(0.0)
406#endif
407{
408}
409
410FastMixerDumpState::~FastMixerDumpState()
411{
412}
413
414void FastMixerDumpState::dump(int fd)
415{
416#define COMMAND_MAX 32
417    char string[COMMAND_MAX];
418    switch (mCommand) {
419    case FastMixerState::INITIAL:
420        strcpy(string, "INITIAL");
421        break;
422    case FastMixerState::HOT_IDLE:
423        strcpy(string, "HOT_IDLE");
424        break;
425    case FastMixerState::COLD_IDLE:
426        strcpy(string, "COLD_IDLE");
427        break;
428    case FastMixerState::EXIT:
429        strcpy(string, "EXIT");
430        break;
431    case FastMixerState::MIX:
432        strcpy(string, "MIX");
433        break;
434    case FastMixerState::WRITE:
435        strcpy(string, "WRITE");
436        break;
437    case FastMixerState::MIX_WRITE:
438        strcpy(string, "MIX_WRITE");
439        break;
440    default:
441        snprintf(string, COMMAND_MAX, "%d", mCommand);
442        break;
443    }
444    fdprintf(fd, "FastMixer command=%s writeSequence=%u framesWritten=%u\n"
445                 "          numTracks=%u writeErrors=%u underruns=%u overruns=%u\n",
446                 string, mWriteSequence, mFramesWritten,
447                 mNumTracks, mWriteErrors, mUnderruns, mOverruns);
448#ifdef FAST_MIXER_STATISTICS
449    fdprintf(fd, "          cycle time in ms: mean=%.1f min=%.1f max=%.1f stddev=%.1f\n",
450                 mMean*1e3, mMinimum*1e3, mMaximum*1e3, mStddev*1e3);
451#endif
452}
453
454}   // namespace android
455