MonoPipe.cpp revision 4d0815d694e5a2edb3ce48427de50f55d0f84c0b 
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 "MonoPipe"
18//#define LOG_NDEBUG 0
19
20#include <common_time/cc_helper.h>
21#include <cutils/atomic.h>
22#include <cutils/compiler.h>
23#include <utils/LinearTransform.h>
24#include <utils/Log.h>
25#include <utils/Trace.h>
26#include <media/AudioBufferProvider.h>
27#include <media/nbaio/MonoPipe.h>
28#include <media/nbaio/roundup.h>
29
30
31namespace android {
32
33MonoPipe::MonoPipe(size_t reqFrames, NBAIO_Format format, bool writeCanBlock) :
34        NBAIO_Sink(format),
35        mUpdateSeq(0),
36        mReqFrames(reqFrames),
37        mMaxFrames(roundup(reqFrames)),
38        mBuffer(malloc(mMaxFrames * Format_frameSize(format))),
39        mFront(0),
40        mRear(0),
41        mWriteTsValid(false),
42        // mWriteTs
43        mSetpoint((reqFrames * 11) / 16),
44        mWriteCanBlock(writeCanBlock),
45        mIsShutdown(false),
46        // mTimestampShared
47        mTimestampMutator(&mTimestampShared),
48        mTimestampObserver(&mTimestampShared)
49{
50    CCHelper tmpHelper;
51    status_t res;
52    uint64_t N, D;
53
54    mNextRdPTS = AudioBufferProvider::kInvalidPTS;
55
56    mSamplesToLocalTime.a_zero = 0;
57    mSamplesToLocalTime.b_zero = 0;
58    mSamplesToLocalTime.a_to_b_numer = 0;
59    mSamplesToLocalTime.a_to_b_denom = 0;
60
61    D = Format_sampleRate(format);
62    if (OK != (res = tmpHelper.getLocalFreq(&N))) {
63        ALOGE("Failed to fetch local time frequency when constructing a"
64              " MonoPipe (res = %d).  getNextWriteTimestamp calls will be"
65              " non-functional", res);
66        return;
67    }
68
69    LinearTransform::reduce(&N, &D);
70    static const uint64_t kSignedHiBitsMask   = ~(0x7FFFFFFFull);
71    static const uint64_t kUnsignedHiBitsMask = ~(0xFFFFFFFFull);
72    if ((N & kSignedHiBitsMask) || (D & kUnsignedHiBitsMask)) {
73        ALOGE("Cannot reduce sample rate to local clock frequency ratio to fit"
74              " in a 32/32 bit rational.  (max reduction is 0x%016llx/0x%016llx"
75              ").  getNextWriteTimestamp calls will be non-functional", N, D);
76        return;
77    }
78
79    mSamplesToLocalTime.a_to_b_numer = static_cast<int32_t>(N);
80    mSamplesToLocalTime.a_to_b_denom = static_cast<uint32_t>(D);
81}
82
83MonoPipe::~MonoPipe()
84{
85    free(mBuffer);
86}
87
88ssize_t MonoPipe::availableToWrite() const
89{
90    if (CC_UNLIKELY(!mNegotiated)) {
91        return NEGOTIATE;
92    }
93    // uses mMaxFrames not mReqFrames, so allows "over-filling" the pipe beyond requested limit
94    ssize_t ret = mMaxFrames - (mRear - android_atomic_acquire_load(&mFront));
95    ALOG_ASSERT((0 <= ret) && (ret <= mMaxFrames));
96    return ret;
97}
98
99ssize_t MonoPipe::write(const void *buffer, size_t count)
100{
101    if (CC_UNLIKELY(!mNegotiated)) {
102        return NEGOTIATE;
103    }
104    size_t totalFramesWritten = 0;
105    while (count > 0) {
106        // can't return a negative value, as we already checked for !mNegotiated
107        size_t avail = availableToWrite();
108        size_t written = avail;
109        if (CC_LIKELY(written > count)) {
110            written = count;
111        }
112        size_t rear = mRear & (mMaxFrames - 1);
113        size_t part1 = mMaxFrames - rear;
114        if (part1 > written) {
115            part1 = written;
116        }
117        if (CC_LIKELY(part1 > 0)) {
118            memcpy((char *) mBuffer + (rear << mBitShift), buffer, part1 << mBitShift);
119            if (CC_UNLIKELY(rear + part1 == mMaxFrames)) {
120                size_t part2 = written - part1;
121                if (CC_LIKELY(part2 > 0)) {
122                    memcpy(mBuffer, (char *) buffer + (part1 << mBitShift), part2 << mBitShift);
123                }
124            }
125            android_atomic_release_store(written + mRear, &mRear);
126            totalFramesWritten += written;
127        }
128        if (!mWriteCanBlock || mIsShutdown) {
129            break;
130        }
131        count -= written;
132        buffer = (char *) buffer + (written << mBitShift);
133        // Simulate blocking I/O by sleeping at different rates, depending on a throttle.
134        // The throttle tries to keep the mean pipe depth near the setpoint, with a slight jitter.
135        uint32_t ns;
136        if (written > 0) {
137            size_t filled = (mMaxFrames - avail) + written;
138            // FIXME cache these values to avoid re-computation
139            if (filled <= mSetpoint / 2) {
140                // pipe is (nearly) empty, fill quickly
141                ns = written * ( 500000000 / Format_sampleRate(mFormat));
142            } else if (filled <= (mSetpoint * 3) / 4) {
143                // pipe is below setpoint, fill at slightly faster rate
144                ns = written * ( 750000000 / Format_sampleRate(mFormat));
145            } else if (filled <= (mSetpoint * 5) / 4) {
146                // pipe is at setpoint, fill at nominal rate
147                ns = written * (1000000000 / Format_sampleRate(mFormat));
148            } else if (filled <= (mSetpoint * 3) / 2) {
149                // pipe is above setpoint, fill at slightly slower rate
150                ns = written * (1150000000 / Format_sampleRate(mFormat));
151            } else if (filled <= (mSetpoint * 7) / 4) {
152                // pipe is overflowing, fill slowly
153                ns = written * (1350000000 / Format_sampleRate(mFormat));
154            } else {
155                // pipe is severely overflowing
156                ns = written * (1750000000 / Format_sampleRate(mFormat));
157            }
158        } else {
159            ns = count * (1350000000 / Format_sampleRate(mFormat));
160        }
161        if (ns > 999999999) {
162            ns = 999999999;
163        }
164        struct timespec nowTs;
165        bool nowTsValid = !clock_gettime(CLOCK_MONOTONIC, &nowTs);
166        // deduct the elapsed time since previous write() completed
167        if (nowTsValid && mWriteTsValid) {
168            time_t sec = nowTs.tv_sec - mWriteTs.tv_sec;
169            long nsec = nowTs.tv_nsec - mWriteTs.tv_nsec;
170            ALOGE_IF(sec < 0 || (sec == 0 && nsec < 0),
171                    "clock_gettime(CLOCK_MONOTONIC) failed: was %ld.%09ld but now %ld.%09ld",
172                    mWriteTs.tv_sec, mWriteTs.tv_nsec, nowTs.tv_sec, nowTs.tv_nsec);
173            if (nsec < 0) {
174                --sec;
175                nsec += 1000000000;
176            }
177            if (sec == 0) {
178                if ((long) ns > nsec) {
179                    ns -= nsec;
180                } else {
181                    ns = 0;
182                }
183            }
184        }
185        if (ns > 0) {
186            const struct timespec req = {0, ns};
187            nanosleep(&req, NULL);
188        }
189        // record the time that this write() completed
190        if (nowTsValid) {
191            mWriteTs = nowTs;
192            if ((mWriteTs.tv_nsec += ns) >= 1000000000) {
193                mWriteTs.tv_nsec -= 1000000000;
194                ++mWriteTs.tv_sec;
195            }
196        }
197        mWriteTsValid = nowTsValid;
198    }
199    mFramesWritten += totalFramesWritten;
200    return totalFramesWritten;
201}
202
203void MonoPipe::setAvgFrames(size_t setpoint)
204{
205    mSetpoint = setpoint;
206}
207
208status_t MonoPipe::getNextWriteTimestamp(int64_t *timestamp)
209{
210    int32_t front;
211
212    ALOG_ASSERT(NULL != timestamp);
213
214    if (0 == mSamplesToLocalTime.a_to_b_denom)
215        return UNKNOWN_ERROR;
216
217    observeFrontAndNRPTS(&front, timestamp);
218
219    if (AudioBufferProvider::kInvalidPTS != *timestamp) {
220        // If we have a valid read-pointer and next read timestamp pair, then
221        // use the current value of the write pointer to figure out how many
222        // frames are in the buffer, and offset the timestamp by that amt.  Then
223        // next time we write to the MonoPipe, the data will hit the speakers at
224        // the next read timestamp plus the current amount of data in the
225        // MonoPipe.
226        size_t pendingFrames = (mRear - front) & (mMaxFrames - 1);
227        *timestamp = offsetTimestampByAudioFrames(*timestamp, pendingFrames);
228    }
229
230    return OK;
231}
232
233void MonoPipe::updateFrontAndNRPTS(int32_t newFront, int64_t newNextRdPTS)
234{
235    // Set the MSB of the update sequence number to indicate that there is a
236    // multi-variable update in progress.  Use an atomic store with an "acquire"
237    // barrier to make sure that the next operations cannot be re-ordered and
238    // take place before the change to mUpdateSeq is commited..
239    int32_t tmp = mUpdateSeq | 0x80000000;
240    android_atomic_acquire_store(tmp, &mUpdateSeq);
241
242    // Update mFront and mNextRdPTS
243    mFront = newFront;
244    mNextRdPTS = newNextRdPTS;
245
246    // We are finished with the update.  Compute the next sequnce number (which
247    // should be the old sequence number, plus one, and with the MSB cleared)
248    // and then store it in mUpdateSeq using an atomic store with a "release"
249    // barrier so our update operations cannot be re-ordered past the update of
250    // the sequence number.
251    tmp = (tmp + 1) & 0x7FFFFFFF;
252    android_atomic_release_store(tmp, &mUpdateSeq);
253}
254
255void MonoPipe::observeFrontAndNRPTS(int32_t *outFront, int64_t *outNextRdPTS)
256{
257    // Perform an atomic observation of mFront and mNextRdPTS.  Basically,
258    // atomically observe the sequence number, then observer the variables, then
259    // atomically observe the sequence number again.  If the two observations of
260    // the sequence number match, and the update-in-progress bit was not set,
261    // then we know we have a successful atomic observation.  Otherwise, we loop
262    // around and try again.
263    //
264    // Note, it is very important that the observer be a lower priority thread
265    // than the updater.  If the updater is lower than the observer, or they are
266    // the same priority and running with SCHED_FIFO (implying that quantum
267    // based premption is disabled) then we run the risk of deadlock.
268    int32_t seqOne, seqTwo;
269
270    do {
271        seqOne        = android_atomic_acquire_load(&mUpdateSeq);
272        *outFront     = mFront;
273        *outNextRdPTS = mNextRdPTS;
274        seqTwo        = android_atomic_release_load(&mUpdateSeq);
275    } while ((seqOne != seqTwo) || (seqOne & 0x80000000));
276}
277
278int64_t MonoPipe::offsetTimestampByAudioFrames(int64_t ts, size_t audFrames)
279{
280    if (0 == mSamplesToLocalTime.a_to_b_denom)
281        return AudioBufferProvider::kInvalidPTS;
282
283    if (ts == AudioBufferProvider::kInvalidPTS)
284        return AudioBufferProvider::kInvalidPTS;
285
286    int64_t frame_lt_duration;
287    if (!mSamplesToLocalTime.doForwardTransform(audFrames,
288                                                &frame_lt_duration)) {
289        // This should never fail, but if there is a bug which is causing it
290        // to fail, this message would probably end up flooding the logs
291        // because the conversion would probably fail forever.  Log the
292        // error, but then zero out the ratio in the linear transform so
293        // that we don't try to do any conversions from now on.  This
294        // MonoPipe's getNextWriteTimestamp is now broken for good.
295        ALOGE("Overflow when attempting to convert %d audio frames to"
296              " duration in local time.  getNextWriteTimestamp will fail from"
297              " now on.", audFrames);
298        mSamplesToLocalTime.a_to_b_numer = 0;
299        mSamplesToLocalTime.a_to_b_denom = 0;
300        return AudioBufferProvider::kInvalidPTS;
301    }
302
303    return ts + frame_lt_duration;
304}
305
306void MonoPipe::shutdown(bool newState)
307{
308    mIsShutdown = newState;
309}
310
311bool MonoPipe::isShutdown()
312{
313    return mIsShutdown;
314}
315
316status_t MonoPipe::getTimestamp(AudioTimestamp& timestamp)
317{
318    if (mTimestampObserver.poll(timestamp)) {
319        return OK;
320    }
321    return INVALID_OPERATION;
322}
323
324}   // namespace android
325