[chromecast] Add --audio-output-sample-rate for Fuchsia

It is possible to set fixed sample rate in cast_shell on Linux with
--alsa-fixed-output-sample-rate, but it wasn't possible on Fuchsia.
Added --audio-output-sample-rate, which allows to set fixed sample rate
on both platforms. For backward compatibility kept the old ALSA-specific
flag, but it's marked as deprecated now.

Bug: 772488
Change-Id: I0f980f09b432768ff9bb51191a9b1ec31e89274f
Reviewed-on: https://chromium-review.googlesource.com/798066Reviewed-by: Luke Halliwell <halliwell@chromium.org>
Reviewed-by: Kenneth MacKay <kmackay@chromium.org>
Commit-Queue: Sergey Ulanov <sergeyu@chromium.org>
Cr-Commit-Position: refs/heads/master@{#521050}

chromecast/base/chromecast_switches.cc

@@ -69,6 +69,7 @@ const char kAlsaCheckCloseTimeout[] = "alsa-check-close-timeout";
 const char kAlsaEnableUpsampling[] = "alsa-enable-upsampling";
 
 // Optional flag to set a fixed sample rate for the alsa device.
+// Deprecated: Use --audio-output-sample-rate instead.
 const char kAlsaFixedOutputSampleRate[] = "alsa-fixed-output-sample-rate";
 
 // Name of the simple mixer control element that the ALSA-based media library
@@ -96,6 +97,11 @@ const char kMaxOutputVolumeDba1m[] = "max-output-volume-dba1m";
 // value is 2.
 const char kAudioOutputChannels[] = "audio-output-channels";
 
+// Specify fixed sample rate for audio output stream. If this flag is not
+// specified the StreamMixer will choose sample rate based on the sample rate of
+// the media stream.
+const char kAudioOutputSampleRate[] = "audio-output-sample-rate";
+
 // Some platforms typically have very little 'free' memory, but plenty is
 // available in buffers+cached.  For such platforms, configure this amount
 // as the portion of buffers+cached memory that should be treated as

chromecast/base/chromecast_switches.h

@@ -38,6 +38,9 @@ extern const char kPreviousApp[];
 extern const char kAcceptResourceProvider[];
 
 // ALSA-based CMA switches. (Only valid for audio products.)
+// TODO(sergeyu): kAlsaEnableUpsampling and kAlsaCheckCloseTimeout are
+// implemented in StreamMixer, which is not ALSA-specific - it's also used on
+// Fuchsia. Rename these flags.
 extern const char kAlsaOutputBufferSize[];
 extern const char kAlsaOutputPeriodSize[];
 extern const char kAlsaOutputStartThreshold[];
@@ -51,6 +54,7 @@ extern const char kAlsaMuteDeviceName[];
 extern const char kAlsaMuteElementName[];
 extern const char kMaxOutputVolumeDba1m[];
 extern const char kAudioOutputChannels[];
+extern const char kAudioOutputSampleRate[];
 
 // Memory pressure switches
 extern const char kMemPressureSystemReservedKb[];

chromecast/media/cma/backend/alsa/mixer_output_stream_alsa.cc

@@ -143,10 +143,6 @@ void MixerOutputStreamAlsa::SetAlsaWrapperForTest(
   alsa_ = std::move(alsa);
 }
 
-bool MixerOutputStreamAlsa::IsFixedSampleRate() {
-  return fixed_sample_rate_ != kInvalidSampleRate;
-}
-
 bool MixerOutputStreamAlsa::Start(int sample_rate, int channels) {
   if (!alsa_) {
     alsa_ = std::make_unique<AlsaWrapper>();
@@ -427,22 +423,9 @@ void MixerOutputStreamAlsa::DefineAlsaParameters() {
     LOG(DFATAL) << "ALSA avail min must be no larger than the buffer size";
     alsa_avail_min_ = alsa_period_size_;
   }
-
-  fixed_sample_rate_ = GetSwitchValueNonNegativeInt(
-      switches::kAlsaFixedOutputSampleRate, kInvalidSampleRate);
-  if (fixed_sample_rate_ != kInvalidSampleRate) {
-    LOG(INFO) << "Setting fixed sample rate to " << fixed_sample_rate_;
-  }
 }
 
 int MixerOutputStreamAlsa::DetermineOutputRate(int requested_sample_rate) {
-  if (fixed_sample_rate_ != kInvalidSampleRate) {
-    LOG(INFO) << "Requested output rate is " << requested_sample_rate;
-    LOG(INFO) << "Cannot change rate since it is fixed to "
-              << fixed_sample_rate_;
-    return fixed_sample_rate_;
-  }
-
   unsigned int unsigned_output_sample_rate = requested_sample_rate;
 
   // Try the requested sample rate. If the ALSA driver doesn't know how to deal

chromecast/media/cma/backend/alsa/mixer_output_stream_alsa.h

@@ -27,7 +27,6 @@ class MixerOutputStreamAlsa : public MixerOutputStream {
   void SetAlsaWrapperForTest(std::unique_ptr<AlsaWrapper> alsa);
 
   // MixerOutputStream interface.
-  bool IsFixedSampleRate() override;
   bool Start(int requested_sample_rate, int channels) override;
   bool GetTimeUntilUnderrun(base::TimeDelta* result) override;
   int GetSampleRate() override;
@@ -57,9 +56,6 @@ class MixerOutputStreamAlsa : public MixerOutputStream {
 
   void UpdateRenderingDelay(int newly_pushed_frames);
 
-  // Value of --alsa-fixed-output-sample-rate flag if any.
-  int fixed_sample_rate_ = kInvalidSampleRate;
-
   std::unique_ptr<AlsaWrapper> alsa_;
 
   snd_pcm_t* pcm_ = nullptr;

chromecast/media/cma/backend/fuchsia/mixer_output_stream_fuchsia.cc

@@ -39,10 +39,6 @@ MixerOutputStreamFuchsia::~MixerOutputStreamFuchsia() {
     fuchsia_audio_manager_free(manager_);
 }
 
-bool MixerOutputStreamFuchsia::IsFixedSampleRate() {
-  return false;
-}
-
 bool MixerOutputStreamFuchsia::Start(int requested_sample_rate, int channels) {
   DCHECK(!stream_);
 

chromecast/media/cma/backend/fuchsia/mixer_output_stream_fuchsia.h

@@ -21,7 +21,6 @@ class MixerOutputStreamFuchsia : public MixerOutputStream {
   ~MixerOutputStreamFuchsia() override;
 
   // MixerOutputStream interface.
-  bool IsFixedSampleRate() override;
   bool Start(int requested_sample_rate, int channels) override;
   bool GetTimeUntilUnderrun(base::TimeDelta* result) override;
   int GetSampleRate() override;

chromecast/media/cma/backend/mixer_output_stream.h

@@ -26,9 +26,6 @@ class MixerOutputStream {
 
   virtual ~MixerOutputStream() {}
 
-  // Returns true if the sample rate is fixed.
-  virtual bool IsFixedSampleRate() = 0;
-
   // Start the stream. Caller must call GetSampleRate() to get the actual sample
   // rate selected for the stream. It may be different from
   // |requested_sample_rate|, e.g. if IsFixedSampleRate() is true, or the device

chromecast/media/cma/backend/stream_mixer.cc

@@ -11,7 +11,6 @@
 #include <utility>
 
 #include "base/bind_helpers.h"
-#include "base/command_line.h"
 #include "base/lazy_instance.h"
 #include "base/memory/ptr_util.h"
 #include "base/memory/weak_ptr.h"
@@ -152,13 +151,27 @@ StreamMixer::StreamMixer()
          num_output_channels_ == 1);
 
   low_sample_rate_cutoff_ =
-      chromecast::GetSwitchValueBoolean(switches::kAlsaEnableUpsampling, false)
+      GetSwitchValueBoolean(switches::kAlsaEnableUpsampling, false)
           ? kLowSampleRateCutoff
           : MixerOutputStream::kInvalidSampleRate;
 
-  // Read post-processing configuration file
-  PostProcessingPipelineParser pipeline_parser;
+  fixed_sample_rate_ = GetSwitchValueNonNegativeInt(
+      switches::kAudioOutputSampleRate, MixerOutputStream::kInvalidSampleRate);
+
+#if defined(USE_ALSA)
+  if (fixed_sample_rate_ == MixerOutputStream::kInvalidSampleRate) {
+    fixed_sample_rate_ =
+        GetSwitchValueNonNegativeInt(switches::kAlsaFixedOutputSampleRate,
+                                     MixerOutputStream::kInvalidSampleRate);
+  }
+#endif  // defined(USE_ALSA)
+
+  if (fixed_sample_rate_ != MixerOutputStream::kInvalidSampleRate) {
+    LOG(INFO) << "Setting fixed sample rate to " << fixed_sample_rate_;
+  }
 
+  // Read post-processing configuration file.
+  PostProcessingPipelineParser pipeline_parser;
   CreatePostProcessors(&pipeline_parser);
 
   // TODO(jyw): command line flag for filter frame alignment.
@@ -166,10 +179,10 @@ StreamMixer::StreamMixer()
       << "Alignment must be a power of 2.";
 
   // --accept-resource-provider should imply a check close timeout of 0.
-  int default_close_timeout = chromecast::GetSwitchValueBoolean(
-                                  switches::kAcceptResourceProvider, false)
-                                  ? 0
-                                  : kDefaultCheckCloseTimeoutMs;
+  int default_close_timeout =
+      GetSwitchValueBoolean(switches::kAcceptResourceProvider, false)
+          ? 0
+          : kDefaultCheckCloseTimeoutMs;
   check_close_timeout_ = GetSwitchValueInt(switches::kAlsaCheckCloseTimeout,
                                            default_close_timeout);
 }
@@ -275,17 +288,20 @@ void StreamMixer::FinishFinalize() {
 bool StreamMixer::Start() {
   DCHECK(mixer_task_runner_->BelongsToCurrentThread());
 
-  int requested_sample_rate = requested_output_samples_per_second_;
-
   if (!output_)
     output_ = MixerOutputStream::Create();
 
-  if (low_sample_rate_cutoff_ != MixerOutputStream::kInvalidSampleRate &&
-      requested_sample_rate < low_sample_rate_cutoff_) {
+  int requested_sample_rate;
+  if (fixed_sample_rate_ != MixerOutputStream::kInvalidSampleRate) {
+    requested_sample_rate = fixed_sample_rate_;
+  } else if (low_sample_rate_cutoff_ != MixerOutputStream::kInvalidSampleRate &&
+             requested_output_samples_per_second_ < low_sample_rate_cutoff_) {
     requested_sample_rate =
         output_samples_per_second_ != MixerOutputStream::kInvalidSampleRate
             ? output_samples_per_second_
             : kLowSampleRateFallback;
+  } else {
+    requested_sample_rate = requested_output_samples_per_second_;
   }
 
   if (!output_->Start(requested_sample_rate, num_output_channels_)) {
@@ -357,7 +373,8 @@ void StreamMixer::AddInput(std::unique_ptr<InputQueue> input) {
   // If the new input is a primary one, we may need to change the output
   // sample rate to match its input sample rate.
   // We only change the output rate if it is not set to a fixed value.
-  if (input->primary() && output_ && !output_->IsFixedSampleRate()) {
+  if (input->primary() && output_ &&
+      fixed_sample_rate_ != MixerOutputStream::kInvalidSampleRate) {
     CheckChangeOutputRate(input->input_samples_per_second());
   }
 

chromecast/media/cma/backend/stream_mixer.h

@@ -281,6 +281,7 @@ class StreamMixer {
   int requested_output_samples_per_second_ = 0;
   int output_samples_per_second_ = 0;
   int low_sample_rate_cutoff_ = 0;
+  int fixed_sample_rate_ = 0;
 
   State state_;