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      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 
     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         // 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 
     83 MonoPipe::~MonoPipe()
     84 {
     85     free(mBuffer);
     86 }
     87 
     88 ssize_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 
     99 ssize_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 
    203 void MonoPipe::setAvgFrames(size_t setpoint)
    204 {
    205     mSetpoint = setpoint;
    206 }
    207 
    208 status_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 
    233 void 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 
    255 void 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 
    278 int64_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 
    306 void MonoPipe::shutdown(bool newState)
    307 {
    308     mIsShutdown = newState;
    309 }
    310 
    311 bool MonoPipe::isShutdown()
    312 {
    313     return mIsShutdown;
    314 }
    315 
    316 status_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