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 "MonoPipeReader"
18 //#define LOG_NDEBUG 0
19
20 #include <cutils/compiler.h>
21 #include <utils/Log.h>
22 #include <media/nbaio/MonoPipeReader.h>
23
24 namespace android {
25
MonoPipeReader(MonoPipe * pipe)26 MonoPipeReader::MonoPipeReader(MonoPipe* pipe) :
27 NBAIO_Source(pipe->mFormat),
28 mPipe(pipe)
29 {
30 }
31
~MonoPipeReader()32 MonoPipeReader::~MonoPipeReader()
33 {
34 }
35
availableToRead()36 ssize_t MonoPipeReader::availableToRead()
37 {
38 if (CC_UNLIKELY(!mNegotiated)) {
39 return NEGOTIATE;
40 }
41 ssize_t ret = android_atomic_acquire_load(&mPipe->mRear) - mPipe->mFront;
42 ALOG_ASSERT((0 <= ret) && (ret <= mMaxFrames));
43 return ret;
44 }
45
read(void * buffer,size_t count,int64_t readPTS)46 ssize_t MonoPipeReader::read(void *buffer, size_t count, int64_t readPTS)
47 {
48 // Compute the "next read PTS" and cache it. Callers of read pass a read
49 // PTS indicating the local time for which they are requesting data along
50 // with a count (which is the number of audio frames they are going to
51 // ultimately pass to the next stage of the pipeline). Offsetting readPTS
52 // by the duration of count will give us the readPTS which will be passed to
53 // us next time, assuming they system continues to operate in steady state
54 // with no discontinuities. We stash this value so it can be used by the
55 // MonoPipe writer to imlement getNextWriteTimestamp.
56 int64_t nextReadPTS;
57 nextReadPTS = mPipe->offsetTimestampByAudioFrames(readPTS, count);
58
59 // count == 0 is unlikely and not worth checking for explicitly; will be handled automatically
60 ssize_t red = availableToRead();
61 if (CC_UNLIKELY(red <= 0)) {
62 // Uh-oh, looks like we are underflowing. Update the next read PTS and
63 // get out.
64 mPipe->updateFrontAndNRPTS(mPipe->mFront, nextReadPTS);
65 return red;
66 }
67 if (CC_LIKELY((size_t) red > count)) {
68 red = count;
69 }
70 size_t front = mPipe->mFront & (mPipe->mMaxFrames - 1);
71 size_t part1 = mPipe->mMaxFrames - front;
72 if (part1 > (size_t) red) {
73 part1 = red;
74 }
75 if (CC_LIKELY(part1 > 0)) {
76 memcpy(buffer, (char *) mPipe->mBuffer + (front << mBitShift), part1 << mBitShift);
77 if (CC_UNLIKELY(front + part1 == mPipe->mMaxFrames)) {
78 size_t part2 = red - part1;
79 if (CC_LIKELY(part2 > 0)) {
80 memcpy((char *) buffer + (part1 << mBitShift), mPipe->mBuffer, part2 << mBitShift);
81 }
82 }
83 mPipe->updateFrontAndNRPTS(red + mPipe->mFront, nextReadPTS);
84 mFramesRead += red;
85 }
86 return red;
87 }
88
onTimestamp(const AudioTimestamp & timestamp)89 void MonoPipeReader::onTimestamp(const AudioTimestamp& timestamp)
90 {
91 mPipe->mTimestampMutator.push(timestamp);
92 }
93
94 } // namespace android
95