Allow audio system to handle synchronized low-latency audio I/O

content/browser/renderer_host/media/audio_renderer_host.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_renderer_host.h"
 
 #include "base/bind.h"
 #include "base/metrics/histogram.h"
 #include "base/process.h"
 #include "base/shared_memory.h"
 #include "content/browser/browser_main_loop.h"
 #include "content/browser/renderer_host/media/audio_sync_reader.h"
 #include "content/common/media/audio_messages.h"
 #include "content/public/browser/media_observer.h"
 #include "media/audio/shared_memory_util.h"
 #include "media/base/audio_bus.h"
 #include "media/base/limits.h"
 
 using content::BrowserMessageFilter;
 using content::BrowserThread;
+using media::AudioBus;
 
 AudioRendererHost::AudioEntry::AudioEntry()
     : stream_id(0),
       pending_close(false) {
 }
 
 AudioRendererHost::AudioEntry::~AudioEntry() {}
 
 ///////////////////////////////////////////////////////////////////////////////
 // AudioRendererHost implementations.
@@ skipping 156 matching lines @@
     IPC_MESSAGE_HANDLER(AudioHostMsg_FlushStream, OnFlushStream)
     IPC_MESSAGE_HANDLER(AudioHostMsg_CloseStream, OnCloseStream)
     IPC_MESSAGE_HANDLER(AudioHostMsg_SetVolume, OnSetVolume)
     IPC_MESSAGE_UNHANDLED(handled = false)
   IPC_END_MESSAGE_MAP_EX()
 
   return handled;
 }
 
 void AudioRendererHost::OnCreateStream(
-    int stream_id, const media::AudioParameters& params) {
+    int stream_id, const media::AudioParameters& params, int input_channels) {
   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::IO));
   DCHECK(LookupById(stream_id) == NULL);
 
   media::AudioParameters audio_params(params);
   uint32 buffer_size = media::AudioBus::CalculateMemorySize(audio_params);
   DCHECK_GT(buffer_size, 0U);
   DCHECK_LE(buffer_size,
             static_cast<uint32>(media::limits::kMaxPacketSizeInBytes));
 
+  DCHECK_GE(input_channels, 0);
+  DCHECK_LT(input_channels, media::limits::kMaxChannels);
+
+  // Calculate output and input memory size.
+  int output_memory_size = AudioBus::CalculateMemorySize(audio_params);
+  DCHECK_GT(output_memory_size, 0);
+
+  int frames = audio_params.frames_per_buffer();
+  int input_memory_size =
+      AudioBus::CalculateMemorySize(input_channels, frames);
+
+  DCHECK_GE(input_memory_size, 0);
+
   scoped_ptr<AudioEntry> entry(new AudioEntry());
 
   // Create the shared memory and share with the renderer process.
+  // For synchronized I/O (if input_channels > 0) then we allocate
+  // extra memory after the output data for the input data.
+  uint32 io_buffer_size = output_memory_size + input_memory_size;
+
   uint32 shared_memory_size =
-      media::TotalSharedMemorySizeInBytes(buffer_size);
+      media::TotalSharedMemorySizeInBytes(io_buffer_size);
   if (!entry->shared_memory.CreateAndMapAnonymous(shared_memory_size)) {
     // If creation of shared memory failed then send an error message.
     SendErrorMessage(stream_id);
     return;
   }
 
   // Create sync reader and try to initialize it.
   scoped_ptr<AudioSyncReader> reader(
-      new AudioSyncReader(&entry->shared_memory, params));
+      new AudioSyncReader(&entry->shared_memory, params, input_channels));
 
   if (!reader->Init()) {
     SendErrorMessage(stream_id);
     return;
   }
 
   // If we have successfully created the SyncReader then assign it to the
   // entry and construct an AudioOutputController.
   entry->reader.reset(reader.release());
   entry->controller = media::AudioOutputController::Create(
@@ skipping 148 matching lines @@
 
   // Iterate the map of entries.
   // TODO(hclam): Implement a faster look up method.
   for (AudioEntryMap::iterator i = audio_entries_.begin();
        i != audio_entries_.end(); ++i) {
     if (!i->second->pending_close && controller == i->second->controller.get())
       return i->second;
   }
   return NULL;
 }