diff --git a/media/libnbaio/MonoPipe.cpp b/media/libnbaio/MonoPipe.cpp
new file mode 100644
index 0000000..c426efb
--- /dev/null
+++ b/media/libnbaio/MonoPipe.cpp
@@ -0,0 +1,299 @@
+/*
+ * 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 <common_time/cc_helper.h>
+#include <cutils/atomic.h>
+#include <cutils/compiler.h>
+#include <utils/LinearTransform.h>
+#include <utils/Log.h>
+#include <utils/Trace.h>
+#include <media/AudioBufferProvider.h>
+#include <media/nbaio/MonoPipe.h>
+#include <media/nbaio/roundup.h>
+
+
+namespace android {
+
+MonoPipe::MonoPipe(size_t reqFrames, NBAIO_Format format, bool writeCanBlock) :
+        NBAIO_Sink(format),
+        mUpdateSeq(0),
+        mReqFrames(reqFrames),
+        mMaxFrames(roundup(reqFrames)),
+        mBuffer(malloc(mMaxFrames * Format_frameSize(format))),
+        mFront(0),
+        mRear(0),
+        mWriteTsValid(false),
+        // mWriteTs
+        mSetpoint((reqFrames * 11) / 16),
+        mWriteCanBlock(writeCanBlock)
+{
+    CCHelper tmpHelper;
+    status_t res;
+    uint64_t N, D;
+
+    mNextRdPTS = AudioBufferProvider::kInvalidPTS;
+
+    mSamplesToLocalTime.a_zero = 0;
+    mSamplesToLocalTime.b_zero = 0;
+    mSamplesToLocalTime.a_to_b_numer = 0;
+    mSamplesToLocalTime.a_to_b_denom = 0;
+
+    D = Format_sampleRate(format);
+    if (OK != (res = tmpHelper.getLocalFreq(&N))) {
+        ALOGE("Failed to fetch local time frequency when constructing a"
+              " MonoPipe (res = %d).  getNextWriteTimestamp calls will be"
+              " non-functional", res);
+        return;
+    }
+
+    LinearTransform::reduce(&N, &D);
+    static const uint64_t kSignedHiBitsMask   = ~(0x7FFFFFFFull);
+    static const uint64_t kUnsignedHiBitsMask = ~(0xFFFFFFFFull);
+    if ((N & kSignedHiBitsMask) || (D & kUnsignedHiBitsMask)) {
+        ALOGE("Cannot reduce sample rate to local clock frequency ratio to fit"
+              " in a 32/32 bit rational.  (max reduction is 0x%016llx/0x%016llx"
+              ").  getNextWriteTimestamp calls will be non-functional", N, D);
+        return;
+    }
+
+    mSamplesToLocalTime.a_to_b_numer = static_cast<int32_t>(N);
+    mSamplesToLocalTime.a_to_b_denom = static_cast<uint32_t>(D);
+}
+
+MonoPipe::~MonoPipe()
+{
+    free(mBuffer);
+}
+
+ssize_t MonoPipe::availableToWrite() const
+{
+    if (CC_UNLIKELY(!mNegotiated)) {
+        return NEGOTIATE;
+    }
+    // uses mMaxFrames not mReqFrames, so allows "over-filling" the pipe beyond requested limit
+    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)
+{
+    if (CC_UNLIKELY(!mNegotiated)) {
+        return NEGOTIATE;
+    }
+    size_t totalFramesWritten = 0;
+    while (count > 0) {
+        // can't return a negative value, as we already checked for !mNegotiated
+        size_t avail = availableToWrite();
+        size_t written = avail;
+        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 (!mWriteCanBlock) {
+            break;
+        }
+        count -= written;
+        buffer = (char *) buffer + (written << mBitShift);
+        // Simulate blocking I/O by sleeping at different rates, depending on a throttle.
+        // The throttle tries to keep the mean pipe depth near the setpoint, with a slight jitter.
+        uint32_t ns;
+        if (written > 0) {
+            size_t filled = (mMaxFrames - avail) + written;
+            // FIXME cache these values to avoid re-computation
+            if (filled <= mSetpoint / 2) {
+                // pipe is (nearly) empty, fill quickly
+                ns = written * ( 500000000 / Format_sampleRate(mFormat));
+            } else if (filled <= (mSetpoint * 3) / 4) {
+                // pipe is below setpoint, fill at slightly faster rate
+                ns = written * ( 750000000 / Format_sampleRate(mFormat));
+            } else if (filled <= (mSetpoint * 5) / 4) {
+                // pipe is at setpoint, fill at nominal rate
+                ns = written * (1000000000 / Format_sampleRate(mFormat));
+            } else if (filled <= (mSetpoint * 3) / 2) {
+                // pipe is above setpoint, fill at slightly slower rate
+                ns = written * (1150000000 / Format_sampleRate(mFormat));
+            } else if (filled <= (mSetpoint * 7) / 4) {
+                // pipe is overflowing, fill slowly
+                ns = written * (1350000000 / Format_sampleRate(mFormat));
+            } else {
+                // pipe is severely overflowing
+                ns = written * (1750000000 / Format_sampleRate(mFormat));
+            }
+        } else {
+            ns = count * (1350000000 / Format_sampleRate(mFormat));
+        }
+        if (ns > 999999999) {
+            ns = 999999999;
+        }
+        struct timespec nowTs;
+        bool nowTsValid = !clock_gettime(CLOCK_MONOTONIC, &nowTs);
+        // deduct the elapsed time since previous write() completed
+        if (nowTsValid && mWriteTsValid) {
+            time_t sec = nowTs.tv_sec - mWriteTs.tv_sec;
+            long nsec = nowTs.tv_nsec - mWriteTs.tv_nsec;
+            if (nsec < 0) {
+                --sec;
+                nsec += 1000000000;
+            }
+            if (sec == 0) {
+                if ((long) ns > nsec) {
+                    ns -= nsec;
+                } else {
+                    ns = 0;
+                }
+            }
+        }
+        if (ns > 0) {
+            const struct timespec req = {0, ns};
+            nanosleep(&req, NULL);
+        }
+        // record the time that this write() completed
+        if (nowTsValid) {
+            mWriteTs = nowTs;
+            if ((mWriteTs.tv_nsec += ns) >= 1000000000) {
+                mWriteTs.tv_nsec -= 1000000000;
+                ++mWriteTs.tv_sec;
+            }
+        }
+        mWriteTsValid = nowTsValid;
+    }
+    mFramesWritten += totalFramesWritten;
+    return totalFramesWritten;
+}
+
+void MonoPipe::setAvgFrames(size_t setpoint)
+{
+    mSetpoint = setpoint;
+}
+
+status_t MonoPipe::getNextWriteTimestamp(int64_t *timestamp)
+{
+    int32_t front;
+
+    ALOG_ASSERT(NULL != timestamp);
+
+    if (0 == mSamplesToLocalTime.a_to_b_denom)
+        return UNKNOWN_ERROR;
+
+    observeFrontAndNRPTS(&front, timestamp);
+
+    if (AudioBufferProvider::kInvalidPTS != *timestamp) {
+        // If we have a valid read-pointer and next read timestamp pair, then
+        // use the current value of the write pointer to figure out how many
+        // frames are in the buffer, and offset the timestamp by that amt.  Then
+        // next time we write to the MonoPipe, the data will hit the speakers at
+        // the next read timestamp plus the current amount of data in the
+        // MonoPipe.
+        size_t pendingFrames = (mRear - front) & (mMaxFrames - 1);
+        *timestamp = offsetTimestampByAudioFrames(*timestamp, pendingFrames);
+    }
+
+    return OK;
+}
+
+void MonoPipe::updateFrontAndNRPTS(int32_t newFront, int64_t newNextRdPTS)
+{
+    // Set the MSB of the update sequence number to indicate that there is a
+    // multi-variable update in progress.  Use an atomic store with an "acquire"
+    // barrier to make sure that the next operations cannot be re-ordered and
+    // take place before the change to mUpdateSeq is commited..
+    int32_t tmp = mUpdateSeq | 0x80000000;
+    android_atomic_acquire_store(tmp, &mUpdateSeq);
+
+    // Update mFront and mNextRdPTS
+    mFront = newFront;
+    mNextRdPTS = newNextRdPTS;
+
+    // We are finished with the update.  Compute the next sequnce number (which
+    // should be the old sequence number, plus one, and with the MSB cleared)
+    // and then store it in mUpdateSeq using an atomic store with a "release"
+    // barrier so our update operations cannot be re-ordered past the update of
+    // the sequence number.
+    tmp = (tmp + 1) & 0x7FFFFFFF;
+    android_atomic_release_store(tmp, &mUpdateSeq);
+}
+
+void MonoPipe::observeFrontAndNRPTS(int32_t *outFront, int64_t *outNextRdPTS)
+{
+    // Perform an atomic observation of mFront and mNextRdPTS.  Basically,
+    // atomically observe the sequence number, then observer the variables, then
+    // atomically observe the sequence number again.  If the two observations of
+    // the sequence number match, and the update-in-progress bit was not set,
+    // then we know we have a successful atomic observation.  Otherwise, we loop
+    // around and try again.
+    //
+    // Note, it is very important that the observer be a lower priority thread
+    // than the updater.  If the updater is lower than the observer, or they are
+    // the same priority and running with SCHED_FIFO (implying that quantum
+    // based premption is disabled) then we run the risk of deadlock.
+    int32_t seqOne, seqTwo;
+
+    do {
+        seqOne        = android_atomic_acquire_load(&mUpdateSeq);
+        *outFront     = mFront;
+        *outNextRdPTS = mNextRdPTS;
+        seqTwo        = android_atomic_release_load(&mUpdateSeq);
+    } while ((seqOne != seqTwo) || (seqOne & 0x80000000));
+}
+
+int64_t MonoPipe::offsetTimestampByAudioFrames(int64_t ts, size_t audFrames)
+{
+    if (0 == mSamplesToLocalTime.a_to_b_denom)
+        return AudioBufferProvider::kInvalidPTS;
+
+    if (ts == AudioBufferProvider::kInvalidPTS)
+        return AudioBufferProvider::kInvalidPTS;
+
+    int64_t frame_lt_duration;
+    if (!mSamplesToLocalTime.doForwardTransform(audFrames,
+                                                &frame_lt_duration)) {
+        // This should never fail, but if there is a bug which is causing it
+        // to fail, this message would probably end up flooding the logs
+        // because the conversion would probably fail forever.  Log the
+        // error, but then zero out the ratio in the linear transform so
+        // that we don't try to do any conversions from now on.  This
+        // MonoPipe's getNextWriteTimestamp is now broken for good.
+        ALOGE("Overflow when attempting to convert %d audio frames to"
+              " duration in local time.  getNextWriteTimestamp will fail from"
+              " now on.", audFrames);
+        mSamplesToLocalTime.a_to_b_numer = 0;
+        mSamplesToLocalTime.a_to_b_denom = 0;
+        return AudioBufferProvider::kInvalidPTS;
+    }
+
+    return ts + frame_lt_duration;
+}
+
+}   // namespace android