Non-blocking audio I/O interface, WIP
Yet another abstraction similar to AudioTrack::Buffer and AudioBufferProvider,
but with support for streaming, non-blocking, and eventually PTS.
This is intended to be used as follows:
- primary HAL output stream implements a Sink
- primary HAL input stream implements a Source
- Pipe implements a Sink
- PipeReader implements a Source or TimedSource (not shown yet),
which supports "read at PTS"
- fast AudioTrack on server side will implement a Source using cblk
- normal AudioTrack on server side will not be changed initially
- fast AudioRecord on server side will implement a Sink using cblk
- normal AudioRecord on server side will not be changed initially
- fast mixer thread will read from Sources and write to a Sink,
or (unlikely) implement a Source and multiple Sinks
- Visualization and PCM logger will read from Source or TimedSource
- A2DP normal mixer will be connected directly to its output stream
and there will be a kind of OutputTrack for duplication that will
read from a Sink with non-blocking write fed by the fast mixer.
Patch set 3 changes:
- Add more implementations of NBAIO interfaces:
added SourceAudioBufferProvider, MonoPipe, MonoPipeReader.
- Added Format_sampleRate and Format_channelCount.
- Extract out the roundUp() method.
- Respond to most comments from previous code review.
- The new classes are untested.
Patch set 4 changes:
- Fix bugs in MonoPipe::write() and MonoPipeReader::read()
- Fix bug initializing mFrameBitShift too early
- renamed roundUp() to roundup()
- Fix Android.mk
- Add LOG_TAG an LOG_NDEBUG, use ALOG_ASSERT and utils/Log.h instead of assert
- Fix build warnings
- Move constructor and destructor bodies from .h to .cpp
- Line length 100
- Following naming conventions for #include double-include protector macros
- Include what you use
- More NBAIO logging
- MonoPipe write can be blocking
Patch set 5 changes:
- Address code review comments
- Use a static library so unused implementations don't take memory
- Comment out libsndfile dependency
- Remove debugging LOGV and LOG_NDEBUG
Patch set 6 changes (would be 6 at old location, actually 2 at new location):
- Address code review comments on patchset 5
- For MonoPipe, allow the full pipe to be used, no need to omit one slot
- Don't do atomic releasing stores unless needed
Still to do:
- I'm not happy with the Pipe class names
- Update build/ for new static library?
Change-Id: Ie6c61f05ce06b676b033be448a8ef9025a2ffcfd
diff --git a/services/audioflinger/MonoPipe.cpp b/services/audioflinger/MonoPipe.cpp
new file mode 100644
index 0000000..b0ddf83
--- /dev/null
+++ b/services/audioflinger/MonoPipe.cpp
@@ -0,0 +1,102 @@
+/*
+ * Copyright (C) 2012 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#define LOG_TAG "MonoPipe"
+//#define LOG_NDEBUG 0
+
+#include <cutils/atomic.h>
+#include <cutils/compiler.h>
+#include <utils/Log.h>
+#include "MonoPipe.h"
+#include "roundup.h"
+
+namespace android {
+
+MonoPipe::MonoPipe(size_t maxFrames, NBAIO_Format format, bool writeCanBlock) :
+ NBAIO_Sink(format),
+ mMaxFrames(roundup(maxFrames)),
+ mBuffer(malloc(mMaxFrames * Format_frameSize(format))),
+ mFront(0),
+ mRear(0),
+ mWriteCanBlock(writeCanBlock)
+{
+ if (writeCanBlock) {
+ // compute sleep time to be about 2/3 of a full pipe;
+ // this gives a balance between risk of underrun vs. too-frequent wakeups
+ mSleep.tv_sec = 0;
+ uint64_t ns = mMaxFrames * (666666667 / Format_sampleRate(format));
+ if (ns > 999999999) {
+ ns = 999999999;
+ }
+ mSleep.tv_nsec = ns;
+ }
+}
+
+MonoPipe::~MonoPipe()
+{
+ free(mBuffer);
+}
+
+ssize_t MonoPipe::availableToWrite() const
+{
+ if (CC_UNLIKELY(!mNegotiated)) {
+ return NEGOTIATE;
+ }
+ ssize_t ret = mMaxFrames - (mRear - android_atomic_acquire_load(&mFront));
+ ALOG_ASSERT((0 <= ret) && (ret <= mMaxFrames));
+ return ret;
+}
+
+ssize_t MonoPipe::write(const void *buffer, size_t count)
+{
+ // count == 0 is unlikely and not worth checking for explicitly; will be handled automatically
+ if (CC_UNLIKELY(!mNegotiated)) {
+ return NEGOTIATE;
+ }
+ size_t totalFramesWritten = 0;
+ for (;;) {
+ size_t written = availableToWrite();
+ if (CC_LIKELY(written > count)) {
+ written = count;
+ }
+ size_t rear = mRear & (mMaxFrames - 1);
+ size_t part1 = mMaxFrames - rear;
+ if (part1 > written) {
+ part1 = written;
+ }
+ if (CC_LIKELY(part1 > 0)) {
+ memcpy((char *) mBuffer + (rear << mBitShift), buffer, part1 << mBitShift);
+ if (CC_UNLIKELY(rear + part1 == mMaxFrames)) {
+ size_t part2 = written - part1;
+ if (CC_LIKELY(part2 > 0)) {
+ memcpy(mBuffer, (char *) buffer + (part1 << mBitShift), part2 << mBitShift);
+ }
+ }
+ android_atomic_release_store(written + mRear, &mRear);
+ totalFramesWritten += written;
+ }
+ if ((count -= written) == 0 || !mWriteCanBlock) {
+ break;
+ }
+ buffer = (char *) buffer + (written << mBitShift);
+ // simulate blocking I/O by sleeping
+ nanosleep(&mSleep, NULL);
+ }
+ mFramesWritten += totalFramesWritten;
+ return totalFramesWritten;
+}
+
+} // namespace android