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
31 namespace android {
32
MonoPipe(size_t reqFrames,NBAIO_Format format,bool writeCanBlock)33 MonoPipe::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 {
47 CCHelper tmpHelper;
48 status_t res;
49 uint64_t N, D;
50
51 mNextRdPTS = AudioBufferProvider::kInvalidPTS;
52
53 mSamplesToLocalTime.a_zero = 0;
54 mSamplesToLocalTime.b_zero = 0;
55 mSamplesToLocalTime.a_to_b_numer = 0;
56 mSamplesToLocalTime.a_to_b_denom = 0;
57
58 D = Format_sampleRate(format);
59 if (OK != (res = tmpHelper.getLocalFreq(&N))) {
60 ALOGE("Failed to fetch local time frequency when constructing a"
61 " MonoPipe (res = %d). getNextWriteTimestamp calls will be"
62 " non-functional", res);
63 return;
64 }
65
66 LinearTransform::reduce(&N, &D);
67 static const uint64_t kSignedHiBitsMask = ~(0x7FFFFFFFull);
68 static const uint64_t kUnsignedHiBitsMask = ~(0xFFFFFFFFull);
69 if ((N & kSignedHiBitsMask) || (D & kUnsignedHiBitsMask)) {
70 ALOGE("Cannot reduce sample rate to local clock frequency ratio to fit"
71 " in a 32/32 bit rational. (max reduction is 0x%016llx/0x%016llx"
72 "). getNextWriteTimestamp calls will be non-functional", N, D);
73 return;
74 }
75
76 mSamplesToLocalTime.a_to_b_numer = static_cast<int32_t>(N);
77 mSamplesToLocalTime.a_to_b_denom = static_cast<uint32_t>(D);
78 }
79
~MonoPipe()80 MonoPipe::~MonoPipe()
81 {
82 free(mBuffer);
83 }
84
availableToWrite() const85 ssize_t MonoPipe::availableToWrite() const
86 {
87 if (CC_UNLIKELY(!mNegotiated)) {
88 return NEGOTIATE;
89 }
90 // uses mMaxFrames not mReqFrames, so allows "over-filling" the pipe beyond requested limit
91 ssize_t ret = mMaxFrames - (mRear - android_atomic_acquire_load(&mFront));
92 ALOG_ASSERT((0 <= ret) && (ret <= mMaxFrames));
93 return ret;
94 }
95
write(const void * buffer,size_t count)96 ssize_t MonoPipe::write(const void *buffer, size_t count)
97 {
98 if (CC_UNLIKELY(!mNegotiated)) {
99 return NEGOTIATE;
100 }
101 size_t totalFramesWritten = 0;
102 while (count > 0) {
103 // can't return a negative value, as we already checked for !mNegotiated
104 size_t avail = availableToWrite();
105 size_t written = avail;
106 if (CC_LIKELY(written > count)) {
107 written = count;
108 }
109 size_t rear = mRear & (mMaxFrames - 1);
110 size_t part1 = mMaxFrames - rear;
111 if (part1 > written) {
112 part1 = written;
113 }
114 if (CC_LIKELY(part1 > 0)) {
115 memcpy((char *) mBuffer + (rear << mBitShift), buffer, part1 << mBitShift);
116 if (CC_UNLIKELY(rear + part1 == mMaxFrames)) {
117 size_t part2 = written - part1;
118 if (CC_LIKELY(part2 > 0)) {
119 memcpy(mBuffer, (char *) buffer + (part1 << mBitShift), part2 << mBitShift);
120 }
121 }
122 android_atomic_release_store(written + mRear, &mRear);
123 totalFramesWritten += written;
124 }
125 if (!mWriteCanBlock || mIsShutdown) {
126 break;
127 }
128 count -= written;
129 buffer = (char *) buffer + (written << mBitShift);
130 // Simulate blocking I/O by sleeping at different rates, depending on a throttle.
131 // The throttle tries to keep the mean pipe depth near the setpoint, with a slight jitter.
132 uint32_t ns;
133 if (written > 0) {
134 size_t filled = (mMaxFrames - avail) + written;
135 // FIXME cache these values to avoid re-computation
136 if (filled <= mSetpoint / 2) {
137 // pipe is (nearly) empty, fill quickly
138 ns = written * ( 500000000 / Format_sampleRate(mFormat));
139 } else if (filled <= (mSetpoint * 3) / 4) {
140 // pipe is below setpoint, fill at slightly faster rate
141 ns = written * ( 750000000 / Format_sampleRate(mFormat));
142 } else if (filled <= (mSetpoint * 5) / 4) {
143 // pipe is at setpoint, fill at nominal rate
144 ns = written * (1000000000 / Format_sampleRate(mFormat));
145 } else if (filled <= (mSetpoint * 3) / 2) {
146 // pipe is above setpoint, fill at slightly slower rate
147 ns = written * (1150000000 / Format_sampleRate(mFormat));
148 } else if (filled <= (mSetpoint * 7) / 4) {
149 // pipe is overflowing, fill slowly
150 ns = written * (1350000000 / Format_sampleRate(mFormat));
151 } else {
152 // pipe is severely overflowing
153 ns = written * (1750000000 / Format_sampleRate(mFormat));
154 }
155 } else {
156 ns = count * (1350000000 / Format_sampleRate(mFormat));
157 }
158 if (ns > 999999999) {
159 ns = 999999999;
160 }
161 struct timespec nowTs;
162 bool nowTsValid = !clock_gettime(CLOCK_MONOTONIC, &nowTs);
163 // deduct the elapsed time since previous write() completed
164 if (nowTsValid && mWriteTsValid) {
165 time_t sec = nowTs.tv_sec - mWriteTs.tv_sec;
166 long nsec = nowTs.tv_nsec - mWriteTs.tv_nsec;
167 ALOGE_IF(sec < 0 || (sec == 0 && nsec < 0),
168 "clock_gettime(CLOCK_MONOTONIC) failed: was %ld.%09ld but now %ld.%09ld",
169 mWriteTs.tv_sec, mWriteTs.tv_nsec, nowTs.tv_sec, nowTs.tv_nsec);
170 if (nsec < 0) {
171 --sec;
172 nsec += 1000000000;
173 }
174 if (sec == 0) {
175 if ((long) ns > nsec) {
176 ns -= nsec;
177 } else {
178 ns = 0;
179 }
180 }
181 }
182 if (ns > 0) {
183 const struct timespec req = {0, ns};
184 nanosleep(&req, NULL);
185 }
186 // record the time that this write() completed
187 if (nowTsValid) {
188 mWriteTs = nowTs;
189 if ((mWriteTs.tv_nsec += ns) >= 1000000000) {
190 mWriteTs.tv_nsec -= 1000000000;
191 ++mWriteTs.tv_sec;
192 }
193 }
194 mWriteTsValid = nowTsValid;
195 }
196 mFramesWritten += totalFramesWritten;
197 return totalFramesWritten;
198 }
199
setAvgFrames(size_t setpoint)200 void MonoPipe::setAvgFrames(size_t setpoint)
201 {
202 mSetpoint = setpoint;
203 }
204
getNextWriteTimestamp(int64_t * timestamp)205 status_t MonoPipe::getNextWriteTimestamp(int64_t *timestamp)
206 {
207 int32_t front;
208
209 ALOG_ASSERT(NULL != timestamp);
210
211 if (0 == mSamplesToLocalTime.a_to_b_denom)
212 return UNKNOWN_ERROR;
213
214 observeFrontAndNRPTS(&front, timestamp);
215
216 if (AudioBufferProvider::kInvalidPTS != *timestamp) {
217 // If we have a valid read-pointer and next read timestamp pair, then
218 // use the current value of the write pointer to figure out how many
219 // frames are in the buffer, and offset the timestamp by that amt. Then
220 // next time we write to the MonoPipe, the data will hit the speakers at
221 // the next read timestamp plus the current amount of data in the
222 // MonoPipe.
223 size_t pendingFrames = (mRear - front) & (mMaxFrames - 1);
224 *timestamp = offsetTimestampByAudioFrames(*timestamp, pendingFrames);
225 }
226
227 return OK;
228 }
229
updateFrontAndNRPTS(int32_t newFront,int64_t newNextRdPTS)230 void MonoPipe::updateFrontAndNRPTS(int32_t newFront, int64_t newNextRdPTS)
231 {
232 // Set the MSB of the update sequence number to indicate that there is a
233 // multi-variable update in progress. Use an atomic store with an "acquire"
234 // barrier to make sure that the next operations cannot be re-ordered and
235 // take place before the change to mUpdateSeq is commited..
236 int32_t tmp = mUpdateSeq | 0x80000000;
237 android_atomic_acquire_store(tmp, &mUpdateSeq);
238
239 // Update mFront and mNextRdPTS
240 mFront = newFront;
241 mNextRdPTS = newNextRdPTS;
242
243 // We are finished with the update. Compute the next sequnce number (which
244 // should be the old sequence number, plus one, and with the MSB cleared)
245 // and then store it in mUpdateSeq using an atomic store with a "release"
246 // barrier so our update operations cannot be re-ordered past the update of
247 // the sequence number.
248 tmp = (tmp + 1) & 0x7FFFFFFF;
249 android_atomic_release_store(tmp, &mUpdateSeq);
250 }
251
observeFrontAndNRPTS(int32_t * outFront,int64_t * outNextRdPTS)252 void MonoPipe::observeFrontAndNRPTS(int32_t *outFront, int64_t *outNextRdPTS)
253 {
254 // Perform an atomic observation of mFront and mNextRdPTS. Basically,
255 // atomically observe the sequence number, then observer the variables, then
256 // atomically observe the sequence number again. If the two observations of
257 // the sequence number match, and the update-in-progress bit was not set,
258 // then we know we have a successful atomic observation. Otherwise, we loop
259 // around and try again.
260 //
261 // Note, it is very important that the observer be a lower priority thread
262 // than the updater. If the updater is lower than the observer, or they are
263 // the same priority and running with SCHED_FIFO (implying that quantum
264 // based premption is disabled) then we run the risk of deadlock.
265 int32_t seqOne, seqTwo;
266
267 do {
268 seqOne = android_atomic_acquire_load(&mUpdateSeq);
269 *outFront = mFront;
270 *outNextRdPTS = mNextRdPTS;
271 seqTwo = android_atomic_release_load(&mUpdateSeq);
272 } while ((seqOne != seqTwo) || (seqOne & 0x80000000));
273 }
274
offsetTimestampByAudioFrames(int64_t ts,size_t audFrames)275 int64_t MonoPipe::offsetTimestampByAudioFrames(int64_t ts, size_t audFrames)
276 {
277 if (0 == mSamplesToLocalTime.a_to_b_denom)
278 return AudioBufferProvider::kInvalidPTS;
279
280 if (ts == AudioBufferProvider::kInvalidPTS)
281 return AudioBufferProvider::kInvalidPTS;
282
283 int64_t frame_lt_duration;
284 if (!mSamplesToLocalTime.doForwardTransform(audFrames,
285 &frame_lt_duration)) {
286 // This should never fail, but if there is a bug which is causing it
287 // to fail, this message would probably end up flooding the logs
288 // because the conversion would probably fail forever. Log the
289 // error, but then zero out the ratio in the linear transform so
290 // that we don't try to do any conversions from now on. This
291 // MonoPipe's getNextWriteTimestamp is now broken for good.
292 ALOGE("Overflow when attempting to convert %d audio frames to"
293 " duration in local time. getNextWriteTimestamp will fail from"
294 " now on.", audFrames);
295 mSamplesToLocalTime.a_to_b_numer = 0;
296 mSamplesToLocalTime.a_to_b_denom = 0;
297 return AudioBufferProvider::kInvalidPTS;
298 }
299
300 return ts + frame_lt_duration;
301 }
302
shutdown(bool newState)303 void MonoPipe::shutdown(bool newState)
304 {
305 mIsShutdown = newState;
306 }
307
isShutdown()308 bool MonoPipe::isShutdown()
309 {
310 return mIsShutdown;
311 }
312
313 } // namespace android
314