Support floating-point audio output for Linux

media/audio/pulse/pulse_output.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 "media/audio/pulse/pulse_output.h"
 
 #include <pulse/pulseaudio.h>
 #include <stdint.h>
 
 #include "base/single_thread_task_runner.h"
 #include "base/time/time.h"
 #include "media/audio/audio_device_description.h"
 #include "media/audio/audio_manager_base.h"
 #include "media/audio/pulse/pulse_util.h"
+#include "media/base/audio_sample_types.h"
 
 namespace media {
 
 using pulse::AutoPulseLock;
 using pulse::WaitForOperationCompletion;
 
 // static, pa_stream_notify_cb
 void PulseAudioOutputStream::StreamNotifyCallback(pa_stream* s, void* p_this) {
   PulseAudioOutputStream* stream = static_cast<PulseAudioOutputStream*>(p_this);
 
@@ skipping 11 matching lines @@
 // static, pa_stream_request_cb_t
 void PulseAudioOutputStream::StreamRequestCallback(pa_stream* s, size_t len,
                                                    void* p_this) {
   // Fulfill write request; must always result in a pa_stream_write() call.
   static_cast<PulseAudioOutputStream*>(p_this)->FulfillWriteRequest(len);
 }
 
 PulseAudioOutputStream::PulseAudioOutputStream(const AudioParameters& params,
                                                const std::string& device_id,
                                                AudioManagerBase* manager)
-    : params_(params),
+    : params_(AudioParameters(params.format(),
+                              params.channel_layout(),
+                              params.sample_rate(),
+                              // Ignore the given bits per sample. We
+                              // want 32 because we're outputting
+                              // floats now.

[DaleCurtis, 2016/11/01 23:07:53]

s/ now// -- no need to document the old state of the code :)

[Raymond Toy, 2016/11/01 23:18:50]

Done.

+                              32,
+                              params.frames_per_buffer())),
       device_id_(device_id),
       manager_(manager),
       pa_context_(NULL),
       pa_mainloop_(NULL),
       pa_stream_(NULL),
       volume_(1.0f),
       source_callback_(NULL) {
   CHECK(params_.IsValid());
   audio_bus_ = AudioBus::Create(params_);
 }
@@ skipping 60 matching lines @@
   // Signal to the manager that we're closed and can be removed.
   // This should be the last call in the function as it deletes "this".
   manager_->ReleaseOutputStream(this);
 }
 
 void PulseAudioOutputStream::FulfillWriteRequest(size_t requested_bytes) {
   int bytes_remaining = requested_bytes;
   while (bytes_remaining > 0) {
     void* buffer = NULL;
     size_t bytes_to_fill = params_.GetBytesPerBuffer();
+

[DaleCurtis, 2016/11/01 23:07:53]

Remove?

[Raymond Toy, 2016/11/01 23:18:50]

Done.

     CHECK_GE(pa_stream_begin_write(pa_stream_, &buffer, &bytes_to_fill), 0);
     CHECK_EQ(bytes_to_fill, static_cast<size_t>(params_.GetBytesPerBuffer()));
 
     // NOTE: |bytes_to_fill| may be larger than |requested_bytes| now, this is
     // okay since pa_stream_begin_write() is the authoritative source on how
     // much can be written.
 
     int frames_filled = 0;
     if (source_callback_) {
       const base::TimeDelta delay = pulse::GetHardwareLatency(pa_stream_);
       frames_filled = source_callback_->OnMoreData(
           delay, base::TimeTicks::Now(), 0, audio_bus_.get());
 
       // Zero any unfilled data so it plays back as silence.
       if (frames_filled < audio_bus_->frames()) {
         audio_bus_->ZeroFramesPartial(
             frames_filled, audio_bus_->frames() - frames_filled);
       }
 
       // Note: If this ever changes to output raw float the data must be clipped
       // and sanitized since it may come from an untrusted source such as NaCl.
       audio_bus_->Scale(volume_);
-      audio_bus_->ToInterleaved(
-          audio_bus_->frames(), params_.bits_per_sample() / 8, buffer);
+
+      // Sanitize the samples.  Replace NaN with zero, and then clamp

[DaleCurtis, 2016/11/01 23:07:53]

This should already be done as part of ToInterleaved, no?

[Raymond Toy, 2016/11/01 23:18:50]

Dunno. I didn't look. I was just going by the comment in line 155.

+      // everything to the range [-1,1].
+      audio_bus_->Clamp();
+
+      audio_bus_->ToInterleaved<Float32SampleTypeTraits>(
+          audio_bus_->frames(), reinterpret_cast<float*>(buffer));
     } else {
       memset(buffer, 0, bytes_to_fill);
     }
 
     if (pa_stream_write(pa_stream_, buffer, bytes_to_fill, NULL, 0LL,
                         PA_SEEK_RELATIVE) < 0) {
       if (source_callback_) {
         source_callback_->OnError(this);
       }
     }
@@ skipping 72 matching lines @@
   volume_ = static_cast<float>(volume);
 }
 
 void PulseAudioOutputStream::GetVolume(double* volume) {
   DCHECK(thread_checker_.CalledOnValidThread());
 
   *volume = volume_;
 }
 
 }  // namespace media