Index: third_party/WebKit/Source/platform/audio/PushPullFIFO.cpp |
diff --git a/third_party/WebKit/Source/platform/audio/PushPullFIFO.cpp b/third_party/WebKit/Source/platform/audio/PushPullFIFO.cpp |
new file mode 100644 |
index 0000000000000000000000000000000000000000..30dba03605498a27137349068ea5b923553ebd8c |
--- /dev/null |
+++ b/third_party/WebKit/Source/platform/audio/PushPullFIFO.cpp |
@@ -0,0 +1,127 @@ |
+// Copyright 2016 The Chromium Authors. All rights reserved. |
+// Use of this source code is governed by a BSD-style license that can be |
+// found in the LICENSE file. |
+ |
+#include "platform/audio/PushPullFIFO.h" |
+ |
+#include "wtf/PtrUtil.h" |
+#include <memory> |
+ |
+namespace blink { |
+ |
+PushPullFIFO::PushPullFIFO(unsigned numberOfChannels, size_t fifoLength) |
+ : m_fifoBus(AudioBus::create(numberOfChannels, fifoLength)), |
+ m_fifoLength(static_cast<int>(fifoLength)), |
+ m_framesAvailable(0), |
+ m_indexRead(0), |
+ m_indexWrite(0) {} |
+ |
+PushPullFIFO::~PushPullFIFO() {} |
+ |
+// Push the data from |inputBus| to FIFO. The size of push is determined by |
+// the length of |inputBus|. |
+void PushPullFIFO::push(const AudioBus* inputBus) { |
+ DCHECK(inputBus); |
+ if (!inputBus) |
+ return; |
+ |
+ int inputBusLength = static_cast<int>(inputBus->length()); |
o1ka
2017/01/13 11:23:44
const?
hongchan
2017/01/13 23:29:22
Done.
|
+ int remainder = m_fifoLength - m_indexWrite; |
o1ka
2017/01/13 11:23:44
const?
hongchan
2017/01/13 23:29:22
Done.
|
+ SECURITY_CHECK(inputBusLength < m_fifoLength); |
+ SECURITY_CHECK(m_indexWrite < m_fifoLength); |
+ |
+ // This check catches the overflow; the write index will go over the read |
+ // index. In the case of push overflow, move the read index to the updated |
+ // write index. |
+ bool fifoOverflow = m_fifoLength < inputBusLength + m_framesAvailable; |
+ DCHECK(!fifoOverflow); |
o1ka
2017/01/13 11:23:44
DCHECK means further execution under this conditio
hongchan
2017/01/13 23:29:22
I talked with rtoy@ about these conditions - what'
|
+ |
+ for (unsigned i = 0; i < m_fifoBus->numberOfChannels(); ++i) { |
+ float* fifoBusChannel = m_fifoBus->channel(i)->mutableData(); |
+ const float* inputBusChannel = inputBus->channel(i)->data(); |
+ if (remainder >= inputBusLength) { |
+ // The remainder is big enough for the input data. |
+ memcpy(fifoBusChannel + m_indexWrite, inputBusChannel, |
+ inputBusLength * sizeof(*fifoBusChannel)); |
+ } else { |
+ // The input data overflows the remainder size. Wrap around the index. |
+ memcpy(fifoBusChannel + m_indexWrite, inputBusChannel, |
+ remainder * sizeof(*fifoBusChannel)); |
+ memcpy(fifoBusChannel, inputBusChannel + remainder, |
+ (inputBusLength - remainder) * sizeof(*fifoBusChannel)); |
+ } |
+ } |
+ |
+ // Accumulate the valid number of frames in FIFO. |
+ m_framesAvailable += inputBusLength; |
+ DCHECK_LE(m_framesAvailable, m_fifoLength); |
+ |
+ // Update the write index; wrap it around if necessary. |
+ m_indexWrite = (m_indexWrite + inputBusLength) % m_fifoLength; |
+ if (fifoOverflow) { |
+ m_indexRead = m_indexWrite; |
+ } |
+} |
+ |
+// Pull the data out of FIFO to |outputBus|. If the remaining frames in the FIFO |
+// is less than the frames to pull, provides the remaining frames plus the |
+// silence. |
+void PushPullFIFO::pull(AudioBus* outputBus, size_t framesToPull) { |
o1ka
2017/01/13 11:23:44
Name it framesRequested? framesToPull, framesToFil
hongchan
2017/01/13 23:29:23
Done.
|
+ DCHECK(outputBus); |
+ SECURITY_CHECK(framesToPull <= outputBus->length()); |
+ if (!outputBus) |
+ return; |
+ |
+ // TODO(hongchan): add a mutex here for this operation when two threads are |
+ // introduced. Pulling operation has a higher priority to ensure the audio |
+ // device callback to be uninterrupted. |
+ |
+ int remainder = m_fifoLength - m_indexRead; |
+ int framesToProvide = static_cast<int>(framesToPull); |
o1ka
2017/01/13 11:23:44
This is not safe cast. Switch interface to int?
o1ka
2017/01/13 11:23:44
both const?
hongchan
2017/01/13 23:29:22
Done.
hongchan
2017/01/13 23:29:23
I have thought about it, but WebAudio has been usi
|
+ SECURITY_CHECK(framesToProvide < m_fifoLength); |
+ SECURITY_CHECK(m_indexRead < m_fifoLength); |
+ |
+ // This check catches the underflow; the read index will go over the write |
+ // index. In the case of underflow, the rest will be filled up with zeros |
+ // (thus glitches). Note that such case does not cause assertion failure |
+ // unlike the pushing process. Pulling an empty FIFO is a valid operation, |
+ // and the consumer will get a block of silence. |
Raymond Toy
2017/01/12 19:29:40
This is a good comment, but I think you really nee
hongchan
2017/01/13 23:29:23
Done.
|
+ int framesToFill = std::min(m_framesAvailable, framesToProvide); |
+ int silentFrames = std::max(0, framesToProvide - m_framesAvailable); |
o1ka
2017/01/13 11:23:44
both const?
o1ka
2017/01/13 11:23:44
Just framesToProvide-framesToFill?
hongchan
2017/01/13 23:29:22
Done.
|
+ |
+ for (unsigned i = 0; i < m_fifoBus->numberOfChannels(); ++i) { |
+ const float* fifoBusChannel = m_fifoBus->channel(i)->data(); |
+ float* outputBusChannel = outputBus->channel(i)->mutableData(); |
+ |
+ // Fill up the output bus with the available frames first. |
+ if (remainder >= framesToFill) { |
+ // The remainder is big enough for the frames to pull. |
+ memcpy(outputBusChannel, fifoBusChannel + m_indexRead, |
+ framesToFill * sizeof(*fifoBusChannel)); |
+ } else { |
+ // The frames to pull is bigger than the remainder size. |
+ // Wrap around the index. |
+ memcpy(outputBusChannel, fifoBusChannel + m_indexRead, |
+ remainder * sizeof(*fifoBusChannel)); |
+ memcpy(outputBusChannel + remainder, fifoBusChannel, |
Raymond Toy
2017/01/12 19:29:40
Should we add DCHECKs here to make sure that we do
hongchan
2017/01/13 23:29:22
I believe this is done by line 81 and 82.
|
+ (framesToFill - remainder) * sizeof(*fifoBusChannel)); |
+ } |
+ |
+ // Then handles the FIFO data shortage if necessary; The frames available |
+ // was not enough to fulfill the requested frames. Fill the rest of the |
+ // channel with silence. |
+ if (silentFrames > 0) { |
+ memset(outputBusChannel + framesToFill, 0, |
+ silentFrames * sizeof(*outputBusChannel)); |
+ } |
+ } |
+ |
+ // Update the read index; wrap it around if necessary. |
+ m_indexRead = (m_indexRead + framesToFill) % m_fifoLength; |
+ |
+ // Decrement the valid number of frames in FIFO. |
+ m_framesAvailable -= framesToFill; |
o1ka
2017/01/13 11:23:44
Something like DCHECK((m_indexRead + m_framesAvail
hongchan
2017/01/13 23:29:22
It seems like a neat idea, but not sure how to mak
|
+ DCHECK_GE(m_framesAvailable, 0); |
+} |
+ |
+} // namespace blink |