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// 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 "base/time/time.h"
#include "build/build_config.h"
#include "media/base/limits.h"
#if defined(OS_ANDROID)
#include "base/android/build_info.h"
#endif
#if defined(OS_MACOSX)
#include "media/base/mac/audio_latency_mac.h"
#endif
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;
v |= v >> 2;
v |= v >> 4;
v |= v >> 8;
v |= v >> 16;
v++;
return v;
}
#endif
} // namespace
// static
bool AudioLatency::IsResamplingPassthroughSupported(LatencyType type) {
#if defined(OS_CHROMEOS)
return true;
#elif defined(OS_ANDROID)
// Only N MR1+ has support for OpenSLES performance modes which allow for
// power efficient playback. Per the Android audio team, we shouldn't waste
// cycles on resampling when using the playback mode. See OpenSLESOutputStream
// for additional implementation details.
return type == LATENCY_PLAYBACK &&
base::android::BuildInfo::GetInstance()->sdk_int() >=
base::android::SDK_VERSION_NOUGAT_MR1;
#else
return false;
#endif
}
// static
int AudioLatency::GetHighLatencyBufferSize(int sample_rate,
int preferred_buffer_size) {
// Empirically, we consider 20ms of samples to be high latency.
const double twenty_ms_size = 2.0 * sample_rate / 100;
#if defined(OS_WIN)
preferred_buffer_size = std::max(preferred_buffer_size, 1);
// Windows doesn't use power of two buffer sizes, so we should always round up
// to the nearest multiple of the output buffer size.
const int high_latency_buffer_size =
std::ceil(twenty_ms_size / preferred_buffer_size) * preferred_buffer_size;
#else
// On other platforms use the nearest higher power of two buffer size. For a
// given sample rate, this works out to:
//
// <= 3200 : 64
// <= 6400 : 128
// <= 12800 : 256
// <= 25600 : 512
// <= 51200 : 1024
// <= 102400 : 2048
// <= 204800 : 4096
//
// On Linux, the minimum hardware buffer size is 512, so the lower calculated
// values are unused. OSX may have a value as low as 128.
const int high_latency_buffer_size = RoundUpToPowerOfTwo(twenty_ms_size);
#endif // defined(OS_WIN)
return std::max(preferred_buffer_size, high_latency_buffer_size);
}
// static
int AudioLatency::GetRtcBufferSize(int sample_rate, int hardware_buffer_size) {
// Use native hardware buffer size as default. On Windows, we strive to open
// up using this native hardware buffer size to achieve best
// possible performance and to ensure that no FIFO is needed on the browser
// side to match the client request. That is why there is no #if case for
// Windows below.
int frames_per_buffer = hardware_buffer_size;
// No |hardware_buffer_size| is specified, fall back to 10 ms buffer size.
if (!frames_per_buffer) {
frames_per_buffer = sample_rate / 100;
DVLOG(1) << "Using 10 ms sink output buffer size: " << frames_per_buffer;
return frames_per_buffer;
}
#if defined(OS_LINUX) || defined(OS_MACOSX) || defined(OS_FUCHSIA)
// On Linux, MacOS and Fuchsia, the low level IO implementations on the
// browser side supports all buffer size the clients want. We use the native
// peer connection buffer size (10ms) to achieve best possible performance.
frames_per_buffer = sample_rate / 100;
#elif defined(OS_ANDROID)
// TODO(olka/henrika): This settings are very old, need to be revisited.
int frames_per_10ms = sample_rate / 100;
if (frames_per_buffer < 2 * frames_per_10ms) {
// Examples of low-latency frame sizes and the resulting |buffer_size|:
// Nexus 7 : 240 audio frames => 2*480 = 960
// Nexus 10 : 256 => 2*441 = 882
// Galaxy Nexus: 144 => 2*441 = 882
frames_per_buffer = 2 * frames_per_10ms;
DVLOG(1) << "Low-latency output detected on Android";
}
#endif
DVLOG(1) << "Using sink output buffer size: " << frames_per_buffer;
return frames_per_buffer;
}
// static
int AudioLatency::GetInteractiveBufferSize(int hardware_buffer_size) {
#if defined(OS_ANDROID)
// Always log this because it's relatively hard to get this
// information out.
LOG(INFO) << "audioHardwareBufferSize = " << hardware_buffer_size;
#endif
return hardware_buffer_size;
}
int AudioLatency::GetExactBufferSize(base::TimeDelta duration,
int sample_rate,
int hardware_buffer_size,
int min_hardware_buffer_size,
int max_hardware_buffer_size) {
DCHECK_NE(0, hardware_buffer_size);
DCHECK_GE(hardware_buffer_size, min_hardware_buffer_size);
DCHECK_GE(max_hardware_buffer_size, min_hardware_buffer_size);
DCHECK(max_hardware_buffer_size == 0 ||
hardware_buffer_size <= max_hardware_buffer_size);
DCHECK(max_hardware_buffer_size == 0 ||
max_hardware_buffer_size <= limits::kMaxWebAudioBufferSize);
int requested_buffer_size = std::round(duration.InSecondsF() * sample_rate);
if (min_hardware_buffer_size &&
requested_buffer_size <= min_hardware_buffer_size)
return min_hardware_buffer_size;
if (requested_buffer_size <= hardware_buffer_size)
return hardware_buffer_size;
#if defined(OS_WIN)
// On Windows we allow either exactly the minimum buffer size (using
// IAudioClient3) or multiples of the default buffer size using the previous
// IAudioClient API.
const int multiplier = hardware_buffer_size;
#else
const int multiplier = min_hardware_buffer_size > 0 ? min_hardware_buffer_size
: hardware_buffer_size;
#endif
int buffer_size =
std::ceil(requested_buffer_size / static_cast<double>(multiplier)) *
multiplier;
// If the user is requesting a buffer size >= max_hardware_buffer_size then we
// want the hardware to run at this max and then only return sizes that are
// multiples of this here so that we don't end up with Web Audio running with
// a period that's misaligned with the hardware one.
if (max_hardware_buffer_size && buffer_size >= max_hardware_buffer_size) {
buffer_size = std::ceil(requested_buffer_size /
static_cast<double>(max_hardware_buffer_size)) *
max_hardware_buffer_size;
}
const int platform_max_buffer_size =
max_hardware_buffer_size
? (limits::kMaxWebAudioBufferSize / max_hardware_buffer_size) *
max_hardware_buffer_size
: (limits::kMaxWebAudioBufferSize / multiplier) * multiplier;
return std::min(buffer_size, platform_max_buffer_size);
}
} // namespace media