Ensure that data is not overwritten in the audio input shared memory ring buffer that sits on the b…

content/browser/renderer_host/media/audio_input_sync_writer.cc

 // Copyright (c) 2012 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 "content/browser/renderer_host/media/audio_input_sync_writer.h"
 
 #include <algorithm>
 
-#include "base/memory/shared_memory.h"
+#include "base/metrics/histogram.h"
+#include "base/strings/stringprintf.h"
 #include "content/browser/renderer_host/media/media_stream_manager.h"
 
 using media::AudioBus;
 
 namespace content {
 
-AudioInputSyncWriter::AudioInputSyncWriter(base::SharedMemory* shared_memory,
+namespace {
+
+// Used to log if any audio glitches have been detected during an audio session.
+// Elements in this enum should not be added, deleted or rearranged.
+enum AudioGlitchResult {
+  AUDIO_CAPTURER_NO_AUDIO_GLITCHES = 0,
+  AUDIO_CAPTURER_AUDIO_GLITCHES = 1,
+  AUDIO_CAPTURER_AUDIO_GLITCHES_MAX = AUDIO_CAPTURER_AUDIO_GLITCHES
+};
+
+}  // namespace
+
+AudioInputSyncWriter::AudioInputSyncWriter(void* shared_memory,
+                                           size_t shared_memory_size,
                                            int shared_memory_segment_count,
                                            const media::AudioParameters& params)
-    : shared_memory_(shared_memory),
+    : shared_memory_(static_cast<uint8*>(shared_memory)),
       shared_memory_segment_count_(shared_memory_segment_count),
       current_segment_id_(0),
       creation_time_(base::Time::Now()),
       audio_bus_memory_size_(AudioBus::CalculateMemorySize(params)),
-      next_buffer_id_(0) {
+      next_buffer_id_(0),
+      next_read_buffer_index_(0),
+      number_of_filled_segments_(0),
+      write_count_(0),
+      write_error_count_(0) {
   DCHECK_GT(shared_memory_segment_count, 0);
-  DCHECK_EQ(shared_memory->requested_size() % shared_memory_segment_count, 0u);
+  DCHECK_EQ(shared_memory_size % shared_memory_segment_count, 0u);
   shared_memory_segment_size_ =
-      shared_memory->requested_size() / shared_memory_segment_count;
-  DVLOG(1) << "SharedMemory::requested_size: "
-           << shared_memory->requested_size();
+      shared_memory_size / shared_memory_segment_count;
+  DVLOG(1) << "shared_memory_size: " << shared_memory_size;
   DVLOG(1) << "shared_memory_segment_count: " << shared_memory_segment_count;
   DVLOG(1) << "audio_bus_memory_size: " << audio_bus_memory_size_;
 
   // Create vector of audio buses by wrapping existing blocks of memory.
-  uint8* ptr = static_cast<uint8*>(shared_memory_->memory());
+  uint8* ptr = shared_memory_;
   for (int i = 0; i < shared_memory_segment_count; ++i) {
     CHECK((reinterpret_cast<uintptr_t>(ptr) &
           (media::AudioBus::kChannelAlignment - 1)) == 0U);
     media::AudioInputBuffer* buffer =
         reinterpret_cast<media::AudioInputBuffer*>(ptr);
     scoped_ptr<media::AudioBus> audio_bus =
         media::AudioBus::WrapMemory(params, buffer->audio);
     audio_buses_.push_back(audio_bus.release());
     ptr += shared_memory_segment_size_;
   }
 }
 
-AudioInputSyncWriter::~AudioInputSyncWriter() {}
+AudioInputSyncWriter::~AudioInputSyncWriter() {
+  if (write_count_ == 0)
+    return;
+
+  UMA_HISTOGRAM_PERCENTAGE(
+      "Media.AudioCapturerMissedReadDeadline",
+      100.0 * write_error_count_ / write_count_);
+
+  UMA_HISTOGRAM_ENUMERATION("Media.AudioCapturerAudioGlitches",
+                            write_error_count_ == 0 ?
+                                AUDIO_CAPTURER_NO_AUDIO_GLITCHES :
+                                AUDIO_CAPTURER_AUDIO_GLITCHES,
+                            AUDIO_CAPTURER_AUDIO_GLITCHES_MAX + 1);
+
+  std::string log_string = base::StringPrintf(
+      "AISW: number of detected audio glitches: %lu out of %lu",
+      write_error_count_,
+      write_count_);
+  MediaStreamManager::SendMessageToNativeLog(log_string);
+  DVLOG(1) << log_string;
+}
 
 void AudioInputSyncWriter::Write(const media::AudioBus* data,
                                  double volume,
                                  bool key_pressed,
                                  uint32 hardware_delay_bytes) {
+  ++write_count_;
+
 #if !defined(OS_ANDROID)
   static const base::TimeDelta kLogDelayThreadhold =
       base::TimeDelta::FromMilliseconds(500);
 
   std::ostringstream oss;
   if (last_write_time_.is_null()) {
     // This is the first time Write is called.
     base::TimeDelta interval = base::Time::Now() - creation_time_;
     oss << "AISW::Write: audio input data received for the first time: delay "
            "= " << interval.InMilliseconds() << "ms";
 
   } else {
     base::TimeDelta interval = base::Time::Now() - last_write_time_;
     if (interval > kLogDelayThreadhold) {
       oss << "AISW::Write: audio input data delay unexpectedly long: delay = "
           << interval.InMilliseconds() << "ms";
     }
   }
   if (!oss.str().empty()) {
-    MediaStreamManager::SendMessageToNativeLog(oss.str());
+    AddToNativeLog(oss.str());
     DVLOG(1) << oss.str();
   }
 
   last_write_time_ = base::Time::Now();
 #endif
 
+  // Check that the renderer side has read data so that we don't overwrite.
+  // The renderer side sends a signal over the socket each time it has read
+  // data. Here, we read those verifications before writing. We verify that each
+  // buffer index is in sequence.
+
+  // Read verifications from other side as long as there is any.
+  while (true) {

[DaleCurtis, 2015/09/03 16:50:40]

If you don't want to use tommi@'s suggestion to read all at once, you can change
this to while (socket_->Peek() >= sizeof(uint32)) {}

[Henrik Grunell, 2015/09/04 11:52:53]

From comment on Peek(): "NOTE: Some implementations cannot reliably determine
the number of bytes available so avoid using the returned size as a promise and
simply test against zero."

Feels safer to just test > 0.

(Side note: Peek should really return bool if the value should be used as such.)

+    if (socket_->Peek() == 0)
+      break;
+
+    uint32 index_read = 0;
+    size_t bytes_received = socket_->ReceiveWithTimeout(

[DaleCurtis, 2015/09/03 16:50:40]

Just use Receive() if you're only going to read what's in Peek().

[Henrik Grunell, 2015/09/04 11:52:53]

Need a timeout since Peek return value isn't reliable.

+        &index_read, sizeof(index_read), base::TimeDelta::FromMilliseconds(5));
+    if (bytes_received != sizeof(index_read)) {

[DaleCurtis, 2015/09/03 16:50:40]

Can make this a dcheck if you take my suggestion above.

[Henrik Grunell, 2015/09/04 11:52:53]

Can't do that based on above.

+      // TODO(grunell): This could happen if this thread has bad luck and
+      // doesn't get to run before the timeout deadline. Otherwise it should
+      // never happen. Best would be to have a non-blocking Receive().
+      break;
+    }
+
+    ++next_read_buffer_index_;
+    CHECK_EQ(index_read, next_read_buffer_index_);
+    --number_of_filled_segments_;
+    CHECK_GE(number_of_filled_segments_, 0);
+  }
+
+  // Check that the ring buffer isn't full and if it is, log error and drop the
+  // buffer.
+  if (number_of_filled_segments_ ==
+      static_cast<int>(shared_memory_segment_count_)) {
+    const std::string error_message =
+        "No room in ring buffer to write data to. Dropping the data.";
+    LOG(ERROR) << error_message;
+    AddToNativeLog(error_message);
+    ++write_error_count_;
+    return;
+  }
+
   // Write audio parameters to shared memory.
-  uint8* ptr = static_cast<uint8*>(shared_memory_->memory());
+  uint8* ptr = shared_memory_;
   ptr += current_segment_id_ * shared_memory_segment_size_;
   media::AudioInputBuffer* buffer =
       reinterpret_cast<media::AudioInputBuffer*>(ptr);
   buffer->params.volume = volume;
   buffer->params.size = audio_bus_memory_size_;
   buffer->params.key_pressed = key_pressed;
   buffer->params.hardware_delay_bytes = hardware_delay_bytes;
   buffer->params.id = next_buffer_id_++;
 
   // Copy data from the native audio layer into shared memory using pre-
   // allocated audio buses.
   media::AudioBus* audio_bus = audio_buses_[current_segment_id_];
   data->CopyTo(audio_bus);
 
   socket_->Send(&current_segment_id_, sizeof(current_segment_id_));
 
   if (++current_segment_id_ >= shared_memory_segment_count_)
     current_segment_id_ = 0;
+
+  ++number_of_filled_segments_;
+  CHECK_LE(number_of_filled_segments_,
+           static_cast<int>(shared_memory_segment_count_));
 }
 
 void AudioInputSyncWriter::Close() {
   socket_->Close();
 }
 
 bool AudioInputSyncWriter::Init() {
   socket_.reset(new base::CancelableSyncSocket());
   foreign_socket_.reset(new base::CancelableSyncSocket());
   return base::CancelableSyncSocket::CreatePair(socket_.get(),
                                                 foreign_socket_.get());
 }
 
 bool AudioInputSyncWriter::PrepareForeignSocket(
     base::ProcessHandle process_handle,
     base::SyncSocket::TransitDescriptor* descriptor) {
   return foreign_socket_->PrepareTransitDescriptor(process_handle, descriptor);
 }
 
+void AudioInputSyncWriter::AddToNativeLog(const std::string& message) {
+  MediaStreamManager::SendMessageToNativeLog(message);
+}
 
 }  // namespace content