Support AudioContextOptions latencyHint as double.

media/base/audio_latency.cc

 // 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 "media/base/audio_latency.h"
 
 #include <stdint.h>
 
 #include <algorithm>
 
 #include "base/logging.h"
 #include "build/build_config.h"
+#include "media/base/audio_parameters.h"
 
 namespace media {
 
 namespace {
 #if !defined(OS_WIN)
 // Taken from "Bit Twiddling Hacks"
 // http://graphics.stanford.edu/~seander/bithacks.html#RoundUpPowerOf2
 uint32_t RoundUpToPowerOfTwo(uint32_t v) {
   v--;
   v |= v >> 1;
@@ skipping 96 matching lines @@
   // the jitter.
   const int kSmallBufferSize = 1024;
   const int kDefaultCallbackBufferSize = 2048;
   if (hardware_buffer_size <= kSmallBufferSize)
     return kDefaultCallbackBufferSize;
 #endif
 
   return hardware_buffer_size;
 }
 
+int AudioLatency::GetExactBufferSize(double duration_in_seconds,

[DaleCurtis, 2017/03/28 17:34:07]

This should take TimeDelta since it's a chromium class.

[Andrew MacPherson, 2017/03/29 08:34:09]

Done.

+                                     const AudioParameters& hardware_params) {
+  const double requested_buffer_size =
+      duration_in_seconds * hardware_params.sample_rate();
+
+  // Round up the requested size to the nearest multiple of the hardware size
+  const int buffer_size = std::ceil(std::max(requested_buffer_size, 1.0) /
+                                    hardware_params.frames_per_buffer()) *
+                          hardware_params.frames_per_buffer();
+
+  return std::max(std::min(buffer_size, GetHighLatencyBufferSize(

[DaleCurtis, 2017/03/28 17:34:07]

Hmm, I don't think these methods should call each other. This should just be the
contents of the if WIN block in GetHighLatencyBufferSize today.

[Andrew MacPherson, 2017/03/29 08:34:09]

Ok, I've modified this as you suggest to just use a 20ms buffer rounded up to
the nearest multiple of the hardware buffer size. Note that this means that
we're clamping the "exact" buffer size maximum to a value lower than the current
"playback" buffer size for some OSes now, since non-Windows OSes were rounding
up the 20ms size to the next power of 2 and not the next multiple of the hw size
before. This is fine with me but just pointing it out.

+                                            hardware_params.sample_rate(), 0)),
+                  static_cast<int>(hardware_params.frames_per_buffer()));
+}
+
 }  // namespace media