[Chromecast] Make ALSA rendering delay either accurate or kNoTimestamp

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

 // Copyright 2015 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 "chromecast/media/cma/backend/alsa/audio_decoder_alsa.h"
 
 #include <time.h>
 
 #include <algorithm>
 #include <limits>
@@ skipping 59 matching lines @@
   delegate_ = delegate;
 }
 
 bool AudioDecoderAlsa::Initialize() {
   TRACE_FUNCTION_ENTRY0();
   DCHECK(delegate_);
   stats_ = Statistics();
   is_eos_ = false;
   last_buffer_pts_ = std::numeric_limits<int64_t>::min();
 
-  struct timespec now;
-  if (clock_gettime(CLOCK_MONOTONIC, &now) == 0) {
-    last_known_delay_.timestamp_microseconds =
-        static_cast<int64_t>(now.tv_sec) * 1000000 + now.tv_nsec / 1000;
-  } else {
-    LOG(ERROR) << "Failed to get current timestamp";
-    last_known_delay_.timestamp_microseconds = kInvalidDelayTimestamp;
-    return false;
-  }
+  last_known_delay_.timestamp_microseconds = kInvalidDelayTimestamp;

[tianyuwang1, 2016/07/08 23:00:00]

Can we use media::kNoTimestamp?

[kmackay, 2016/07/08 23:59:10]

I would prefer not to, since media::kNoTimestamp is a base::TimeDelta.

I could define an int64_t constant in chromecast/media/base, but I'd like to do
that in a separate CL since it would be used outside of this context.

   last_known_delay_.delay_microseconds = 0;
   return true;
 }
 
 bool AudioDecoderAlsa::Start(int64_t start_pts) {
   TRACE_FUNCTION_ENTRY0();
   current_pts_ = start_pts;
   DCHECK(IsValidConfig(config_));
   mixer_input_.reset(new StreamMixerAlsaInput(
       this, config_.samples_per_second, backend_->Primary()));
@@ skipping 195 matching lines @@
   TRACE_FUNCTION_ENTRY0();
   DCHECK(task_runner_->BelongsToCurrentThread());
   if (error != MixerError::kInputIgnored)
     LOG(ERROR) << "Mixer error occurred.";
   error_ = true;
   delegate_->OnDecoderError();
 }
 
 }  // namespace media
 }  // namespace chromecast