ppapi/shared_impl/ppb_audio_config_shared.cc

   1 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style license that can be
   3 // found in the LICENSE file.
   4
   5 #include "build/build_config.h"
   6 #include "ppapi/shared_impl/ppb_audio_config_shared.h"
   7 #include "ppapi/thunk/enter.h"
   8 #include "ppapi/thunk/ppb_instance_api.h"
   9
  10 namespace ppapi {
  11
  12 // Rounds up requested_size to the nearest multiple of minimum_size.
  13 static uint32_t CalculateMultipleOfSampleFrameCount(uint32_t minimum_size,
  14                                                     uint32_t requested_size) {
  15   const uint32_t multiple = (requested_size + minimum_size - 1) / minimum_size;
  16   return std::min(minimum_size * multiple,
  17                   static_cast<uint32_t>(PP_AUDIOMAXSAMPLEFRAMECOUNT));
  18 }
  19
  20 PPB_AudioConfig_Shared::PPB_AudioConfig_Shared(ResourceObjectType type,
  21                                                PP_Instance instance)
  22     : Resource(type, instance),
  23       sample_rate_(PP_AUDIOSAMPLERATE_NONE),
  24       sample_frame_count_(0) {}
  25
  26 PPB_AudioConfig_Shared::~PPB_AudioConfig_Shared() {}
  27
  28 PP_Resource PPB_AudioConfig_Shared::Create(ResourceObjectType type,
  29                                            PP_Instance instance,
  30                                            PP_AudioSampleRate sample_rate,
  31                                            uint32_t sample_frame_count) {
  32   scoped_refptr<PPB_AudioConfig_Shared> object(
  33       new PPB_AudioConfig_Shared(type, instance));
  34   if (!object->Init(sample_rate, sample_frame_count))
  35     return 0;
  36   return object->GetReference();
  37 }
  38
  39 // static
  40 uint32_t PPB_AudioConfig_Shared::RecommendSampleFrameCount_1_0(
  41     PP_AudioSampleRate sample_rate,
  42     uint32_t requested_sample_frame_count) {
  43   // Version 1.0: Don't actually query to get a value from the
  44   // hardware; instead return the input for in-range values.
  45   if (requested_sample_frame_count < PP_AUDIOMINSAMPLEFRAMECOUNT)
  46     return PP_AUDIOMINSAMPLEFRAMECOUNT;
  47   if (requested_sample_frame_count > PP_AUDIOMAXSAMPLEFRAMECOUNT)
  48     return PP_AUDIOMAXSAMPLEFRAMECOUNT;
  49   return requested_sample_frame_count;
  50 }
  51
  52 // static
  53 uint32_t PPB_AudioConfig_Shared::RecommendSampleFrameCount_1_1(
  54     PP_Instance instance,
  55     PP_AudioSampleRate sample_rate,
  56     uint32_t sample_frame_count) {
  57   // Version 1.1: Query the back-end hardware for sample rate and buffer size,
  58   // and recommend a best fit based on request.
  59   thunk::EnterInstanceNoLock enter(instance);
  60   if (enter.failed())
  61     return 0;
  62
  63   // Get the hardware config.
  64   PP_AudioSampleRate hardware_sample_rate = static_cast<PP_AudioSampleRate>(
  65       enter.functions()->GetAudioHardwareOutputSampleRate(instance));
  66   uint32_t hardware_sample_frame_count =
  67       enter.functions()->GetAudioHardwareOutputBufferSize(instance);
  68   if (sample_frame_count < PP_AUDIOMINSAMPLEFRAMECOUNT)
  69     sample_frame_count = PP_AUDIOMINSAMPLEFRAMECOUNT;
  70
  71   // If hardware information isn't available we're connected to a fake audio
  72   // output stream on the browser side, so we can use whatever sample count the
  73   // client wants.
  74   if (!hardware_sample_frame_count || !hardware_sample_rate)
  75     return sample_frame_count;
  76
  77   // Note: All the values below were determined through experimentation to
  78   // minimize jitter and back-to-back callbacks from the browser.  Please take
  79   // care when modifying these values as they impact a large number of users.
  80   // TODO(dalecurtis): Land jitter test and add documentation for updating this.
  81
  82   // Should track the value reported by XP and ALSA backends.
  83   const uint32_t kHighLatencySampleFrameCount = 2048;
  84 #if defined(OS_CHROMEOS) && defined(ARCH_CPU_ARM_FAMILY)
  85   // TODO(ihf): Remove this once ARM Chromebooks support low latency audio. For
  86   // now we classify them as high latency. See crbug.com/289770. Note that
  87   // Adobe Flash is affected but not HTML5, WebRTC and WebAudio (they are using
  88   // real time threads).
  89   const bool kHighLatencyDevice = true;
  90 #else
  91   const bool kHighLatencyDevice = false;
  92 #endif
  93
  94   // If client is using same sample rate as audio hardware, then recommend a
  95   // multiple of the audio hardware's sample frame count.
  96   if (!kHighLatencyDevice && hardware_sample_rate == sample_rate) {
  97     return CalculateMultipleOfSampleFrameCount(hardware_sample_frame_count,
  98                                                sample_frame_count);
  99   }
 100
 101   // If the hardware requires a high latency buffer or we're at a low sample
 102   // rate w/ a buffer that's larger than 10ms, choose the nearest multiple of
 103   // the high latency sample frame count.  An example of too low and too large
 104   // is 16kHz and a sample frame count greater than 160 frames.
 105   if (kHighLatencyDevice ||
 106       hardware_sample_frame_count >= kHighLatencySampleFrameCount ||
 107       (hardware_sample_rate < 44100 &&
 108        hardware_sample_frame_count > hardware_sample_rate / 100u)) {
 109     return CalculateMultipleOfSampleFrameCount(
 110         sample_frame_count,
 111         std::max(kHighLatencySampleFrameCount, hardware_sample_frame_count));
 112   }
 113
 114   // All low latency clients should be able to handle a 512 frame buffer with
 115   // resampling from 44.1kHz and 48kHz to higher sample rates.
 116   // TODO(dalecurtis): We may need to investigate making the callback thread
 117   // high priority to handle buffers at the absolute minimum w/o glitching.
 118   const uint32_t kLowLatencySampleFrameCount = 512;
 119
 120   // Special case for 48kHz -> 44.1kHz and buffer sizes greater than 10ms.  In
 121   // testing most buffer sizes > 10ms led to glitching, so we choose a size we
 122   // know won't cause jitter.
 123   int min_sample_frame_count = kLowLatencySampleFrameCount;
 124   if (hardware_sample_rate == 44100 && sample_rate == 48000 &&
 125       hardware_sample_frame_count > hardware_sample_rate / 100u) {
 126     min_sample_frame_count =
 127         std::max(2 * kLowLatencySampleFrameCount, hardware_sample_frame_count);
 128   }
 129
 130   return CalculateMultipleOfSampleFrameCount(min_sample_frame_count,
 131                                              sample_frame_count);
 132 }
 133
 134 // static
 135 PP_AudioSampleRate PPB_AudioConfig_Shared::RecommendSampleRate(
 136     PP_Instance instance) {
 137   thunk::EnterInstanceNoLock enter(instance);
 138   if (enter.failed())
 139     return PP_AUDIOSAMPLERATE_NONE;
 140   PP_AudioSampleRate hardware_sample_rate = static_cast<PP_AudioSampleRate>(
 141       enter.functions()->GetAudioHardwareOutputSampleRate(instance));
 142   return hardware_sample_rate;
 143 }
 144
 145 thunk::PPB_AudioConfig_API* PPB_AudioConfig_Shared::AsPPB_AudioConfig_API() {
 146   return this;
 147 }
 148
 149 PP_AudioSampleRate PPB_AudioConfig_Shared::GetSampleRate() {
 150   return sample_rate_;
 151 }
 152
 153 uint32_t PPB_AudioConfig_Shared::GetSampleFrameCount() {
 154   return sample_frame_count_;
 155 }
 156
 157 bool PPB_AudioConfig_Shared::Init(PP_AudioSampleRate sample_rate,
 158                                   uint32_t sample_frame_count) {
 159   // TODO(brettw): Currently we don't actually check what the hardware
 160   // supports, so just allow sample rates of the "guaranteed working" ones.
 161   // TODO(dalecurtis): If sample rates are added RecommendSampleFrameCount_1_1()
 162   // must be updated to account for the new rates.
 163   if (sample_rate != PP_AUDIOSAMPLERATE_44100 &&
 164       sample_rate != PP_AUDIOSAMPLERATE_48000)
 165     return false;
 166
 167   // TODO(brettw): Currently we don't actually query to get a value from the
 168   // hardware, so just validate the range.
 169   if (sample_frame_count > PP_AUDIOMAXSAMPLEFRAMECOUNT ||
 170       sample_frame_count < PP_AUDIOMINSAMPLEFRAMECOUNT)
 171     return false;
 172
 173   sample_rate_ = sample_rate;
 174   sample_frame_count_ = sample_frame_count;
 175   return true;
 176 }
 177
 178 }  // namespace ppapi