Add two demos which exercise the audio server.

examples/audio_play_test/play_wav.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 <memory>
+
+#include "base/bind.h"
+#include "base/logging.h"
+#include "mojo/public/c/system/main.h"
+#include "mojo/public/cpp/application/application_delegate.h"
+#include "mojo/public/cpp/application/application_impl.h"
+#include "mojo/public/cpp/application/application_runner.h"
+#include "mojo/public/cpp/system/data_pipe.h"
+#include "mojo/public/cpp/utility/run_loop.h"
+#include "mojo/services/media/audio/interfaces/audio_server.mojom.h"
+#include "mojo/services/media/audio/interfaces/audio_track.mojom.h"
+#include "mojo/services/media/common/cpp/circular_buffer_media_pipe_adapter.h"
+#include "mojo/services/media/common/cpp/linear_transform.h"
+#include "mojo/services/media/common/cpp/local_time.h"
+#include "mojo/services/network/interfaces/network_service.mojom.h"
+#include "mojo/services/network/interfaces/url_loader.mojom.h"
+
+#define PACKED __attribute__((packed))
+
+namespace mojo {
+namespace media {
+namespace audio {
+namespace examples {
+
+#if 0
+static constexpr const char* TEST_FILE =
+  "http://localhost/test_content/piano2.wav";
+#else
+static constexpr const char* TEST_FILE =
+  "http://www.thesoundarchive.com/starwars/swvader04.wav";

[jeffbrown, 2015/11/04 19:34:44]

Is this copyrighted material?

[johngro, 2015/11/05 00:25:16]

The URL?  I don't think that you can copyright a URL.  The use of the content by
the server which responds to this URL is not my business IMO.  I suspect that it
would falls under "fair use", but since I am not a lawyer, who knows?  I
certainly don't have any idea, nor would it be proper for either me or you to
even give the impression that we have any idea.  I do know that I can find this
URL using many popular search engines (like Bing(tm), for example), and that I
can access this content using many popular "Web Browsers" (like Apple(tm)
Safari(tm), for example) and I do not think that anyone doing so is violating
any copyrights.

Like I said before, however, I am not a lawyer and clearly unqualified to have
any opinion about anything, in particular anything involving legal matters.  I
will remove the string from this CL.

+#endif
+static constexpr uint32_t BUF_DEPTH_USEC    = 500000;
+static constexpr uint32_t BUF_LO_WATER_USEC = 400000;
+static constexpr uint32_t BUF_HI_WATER_USEC = 450000;
+static constexpr uint32_t CHUNK_SIZE_USEC   = 10000;
+
+class PlayWAVApp : public ApplicationDelegate {
+ public:
+  ~PlayWAVApp() override { Quit(); }
+
+  // ApplicationDelegate
+  void Initialize(ApplicationImpl* app) override;
+  void Quit() override;
+
+ private:
+  using AudioPipePtr = std::unique_ptr<CircularBufferMediaPipeAdapter>;
+  using AudioPacket  = CircularBufferMediaPipeAdapter::MappedPacket;
+  using PacketCbk    = MediaPipe::SendPacketCallback;
+
+  // TODO(johngro): endianness!
+  struct PACKED RIFFChunkHeader {
+    uint32_t  four_cc;
+    uint32_t  length;
+  };
+
+  struct PACKED WAVHeader {
+    uint32_t  wave_four_cc;
+    uint32_t  fmt_four_cc;
+    uint32_t  fmt_chunk_len;
+    uint16_t  format;
+    uint16_t  channel_count;
+    uint32_t  frame_rate;
+    uint32_t  average_byte_rate;
+    uint16_t  frame_size;
+    uint16_t  bits_per_sample;
+  };
+
+  // TODO(johngro): as mentioned before... endianness!

[jeffbrown, 2015/11/04 19:34:44]

Mentioned where?

[johngro, 2015/11/05 00:25:16]

line 55.

+  static constexpr uint32_t RIFF_FOUR_CC = 'FFIR';
+  static constexpr uint32_t WAVE_FOUR_CC = 'EVAW';
+  static constexpr uint32_t FMT_FOUR_CC  = ' tmf';
+  static constexpr uint32_t DATA_FOUR_CC = 'atad';
+
+  static constexpr uint16_t FORMAT_LPCM  = 0x0001;
+  static constexpr uint16_t FORMAT_MULAW = 0x0101;
+  static constexpr uint16_t FORMAT_ALAW  = 0x0102;
+  static constexpr uint16_t FORMAT_ADPCM = 0x0103;
+
+  static const std::set<std::string> VALID_MIME_TYPES;
+  static const std::set<uint16_t>    VALID_FRAME_RATES;
+  static const std::set<uint16_t>    VALID_BITS_PER_SAMPLES;
+
+  bool BlockingRead(void* buf, uint32_t len);
+  void ProcessHTTPResponse(URLResponsePtr resp);
+  void PlayWAV();
+
+  void OnAudioConfigured(MediaResult res);
+  void OnHasRateControl(MediaResult res);
+  bool OnNeedsData(MediaResult res);
+  void OnPlayoutComplete(MediaResult res);
+
+  uint32_t USecToFrames(uint32_t usec) {
+    uint64_t ret = (static_cast<uint64_t>(usec) * wav_info_.frame_rate)
+                 / 1000000;
+    DCHECK_LT(ret, std::numeric_limits<uint32_t>::max());
+    return ret;
+  }
+
+  uint32_t USecToBytes(uint32_t usec) {
+    uint32_t frames = USecToFrames(usec);
+
+    DCHECK(wav_info_.frame_size);
+    DCHECK_LT(frames,
+              std::numeric_limits<uint32_t>::max() / wav_info_.frame_size);
+
+    return frames * wav_info_.frame_size;
+  }
+
+  AudioServerPtr               audio_server_;
+  AudioTrackPtr                audio_track_;
+  AudioPipePtr                 audio_pipe_;
+  MediaPipePtr                 media_pipe_;
+  RateControlPtr               rate_control_;
+  AudioPacket                  audio_packet_;
+  PacketCbk                    playout_complete_cbk_;
+  NetworkServicePtr            network_service_;
+  URLLoaderPtr                 url_loader_;
+  ScopedDataPipeConsumerHandle payload_;
+  uint32_t                     payload_len_;
+  WAVHeader                    wav_info_;
+  bool                         sent_first_packet_ = false;
+  bool                         clock_started_     = false;
+};
+
+const std::set<std::string> PlayWAVApp::VALID_MIME_TYPES({
+    "audio/x-wav",
+    "audio/wav",
+});
+
+const std::set<uint16_t> PlayWAVApp::VALID_FRAME_RATES({
+  8000, 16000, 24000, 32000, 48000,
+  11025, 22050, 44100,
+});
+
+const std::set<uint16_t> PlayWAVApp::VALID_BITS_PER_SAMPLES({
+  8, 16,
+});
+
+void PlayWAVApp::Initialize(ApplicationImpl* app) {
+  app->ConnectToService("mojo:audio_server", &audio_server_);
+  app->ConnectToService("mojo:network_service", &network_service_);
+
+  network_service_->CreateURLLoader(GetProxy(&url_loader_));
+
+  playout_complete_cbk_ = PacketCbk([this](MediaResult res) {
+                                      this->OnPlayoutComplete(res);
+                                    });
+
+  URLRequestPtr req(URLRequest::New());
+  req->url    = TEST_FILE;
+  req->method = "GET";
+
+  auto cbk = [this](URLResponsePtr resp) { ProcessHTTPResponse(resp.Pass()); };
+  url_loader_->Start(req.Pass(), URLLoader::StartCallback(cbk));
+}
+
+void PlayWAVApp::Quit() {
+  if (audio_packet_.packet()) {
+    DCHECK(audio_pipe_);
+    audio_pipe_->CancelMediaPacket(&audio_packet_);
+  }
+
+  payload_.reset();
+  url_loader_.reset();
+  network_service_.reset();
+  media_pipe_.reset();
+  audio_pipe_.reset();
+  audio_track_.reset();
+  audio_server_.reset();
+}
+
+bool PlayWAVApp::BlockingRead(void* buf, uint32_t op_len) {
+  MojoResult res;
+  uint32_t amt;
+
+  while (true) {
+    amt = op_len;
+    res = ReadDataRaw(payload_.get(), buf, &amt,
+                      MOJO_READ_DATA_FLAG_ALL_OR_NONE);
+
+    if ((res == MOJO_RESULT_SHOULD_WAIT) ||
+        (res == MOJO_RESULT_OUT_OF_RANGE)) {
+      Wait(payload_.get(),

[jeffbrown, 2015/11/04 19:34:44]

Isn't there a non-blocking way to do this?

[johngro, 2015/11/05 00:25:16]

yes; if I understand correctly it involves creating an instance of a
mojo::AsyncWaiter and passing it the handle, the wait conditions, and a
callback.  Whenever the handle meets the signalling conditions, it will invoke
the callback on the main message thread.  From what I can tell, There is no way
to alter the waiter after construction (no way to change the conditions, no way
to mask the callback), so if the handle meets the conditions, but you want to
temporarily halt the callbacks, you need to destroy your waiter and allocate a
new one the next time you want to be called back.  Basically, in this
application, the waiter needs to be..

1) A member of the class (it cannot be bound via closure to the callback because
the callback needs to be bound and passed to the waiter at construction time).
2) Heap allocated/destroyed every time you want to start/stop waiting.

This is lazy example code.  If you want, I will formally restructure this so
that there are absolutely no blocking operations.  If I do, I will go ahead and
eliminate all of the calls to wait on interfaces during setup as well.

+           MOJO_HANDLE_SIGNAL_READABLE,
+           MOJO_DEADLINE_INDEFINITE,
+           nullptr);
+      continue;
+    }
+
+    break;
+  }
+
+  return ((res == MOJO_RESULT_OK) && (amt == op_len));
+}
+
+void PlayWAVApp::ProcessHTTPResponse(URLResponsePtr resp) {
+  if (resp->mime_type.is_null() ||
+     (VALID_MIME_TYPES.find(resp->mime_type) == VALID_MIME_TYPES.end())) {
+    LOG(ERROR) << "Bad MimeType \""
+               << (resp->mime_type.is_null() ? "<null>" : resp->mime_type)
+               << "\"";
+    RunLoop::current()->Quit();
+    return;
+  }
+
+  payload_ = resp->body.Pass();
+
+  // Read and sanity check the top level RIFF header
+  RIFFChunkHeader riff_hdr;
+  if (!BlockingRead(&riff_hdr, sizeof(riff_hdr))) {
+    LOG(ERROR) << "Failed to read top level RIFF header!";
+    RunLoop::current()->Quit();

[jeffbrown, 2015/11/04 19:34:44]

This is telling me that Mojo needs a better pattern for how to terminate
applications... :)

[johngro, 2015/11/05 00:25:16]

Acknowledged.

There is some discussion on the subject here...

https://docs.google.com/document/d/1tKZw3cnnGEuoOD1gYLmPQtqYHNR0swLQLLhm7fV7j...

I don't think that anyone has said anything about this since early July.

+    return;
+  }
+
+  if (riff_hdr.four_cc != RIFF_FOUR_CC) {
+    LOG(ERROR) << "Missing expected 'RIFF' 4CC "
+               << "(expected 0x " << std::hex << RIFF_FOUR_CC
+               << " got 0x"       << std::hex << riff_hdr.four_cc
+               << ")";
+    RunLoop::current()->Quit();
+    return;
+  }
+
+  // Now read the WAVE header along with its required format chunk.
+  if (!BlockingRead(&wav_info_, sizeof(wav_info_))) {
+    LOG(ERROR) << "Failed to read top level WAVE header!";
+    RunLoop::current()->Quit();
+    return;
+  }
+
+  if (wav_info_.wave_four_cc != WAVE_FOUR_CC) {
+    LOG(ERROR) << "Missing expected 'WAVE' 4CC "
+               << "(expected 0x " << std::hex << WAVE_FOUR_CC
+               << " got 0x"       << std::hex << wav_info_.wave_four_cc
+               << ")";
+    RunLoop::current()->Quit();
+    return;
+  }
+
+  // Sanity check the format of the wave file.  This demo only support a limited
+  // subset of the possible formats.
+  if (wav_info_.format != FORMAT_LPCM) {
+    LOG(ERROR) << "Unsupported format (0x"
+               << std::hex << wav_info_.format
+               << ") must be LPCM (0x"
+               << std::hex << FORMAT_LPCM
+               << ")";
+    RunLoop::current()->Quit();
+    return;
+  }
+
+  if ((wav_info_.channel_count != 1) && (wav_info_.channel_count != 2)) {
+    LOG(ERROR) << "Unsupported channel count ("
+               << wav_info_.channel_count
+               << ") must be either mono or stereo";
+    RunLoop::current()->Quit();
+    return;
+  }
+
+  if ((wav_info_.channel_count != 1) && (wav_info_.channel_count != 2)) {

[jeffbrown, 2015/11/04 19:34:44]

duplicate code

[johngro, 2015/11/05 00:25:16]

Done.
good catch.

+    LOG(ERROR) << "Unsupported channel count ("
+               << wav_info_.channel_count
+               << ") must be either mono or stereo";
+    RunLoop::current()->Quit();
+    return;
+  }
+
+  if (VALID_FRAME_RATES.find(wav_info_.frame_rate) == VALID_FRAME_RATES.end()) {
+    LOG(ERROR) << "Unsupported frame_rate (" << wav_info_.frame_rate << ")";
+    RunLoop::current()->Quit();
+    return;
+  }
+
+  if (VALID_BITS_PER_SAMPLES.find(wav_info_.bits_per_sample) ==
+      VALID_BITS_PER_SAMPLES.end()) {
+    LOG(ERROR) << "Unsupported bits per sample (" << wav_info_.bits_per_sample
+               << ")";
+    RunLoop::current()->Quit();
+    return;
+  }
+
+  uint16_t expected_frame_size;
+  expected_frame_size = (wav_info_.channel_count * wav_info_.bits_per_sample)
+                        >> 3;
+  if (wav_info_.frame_size != expected_frame_size) {
+    LOG(ERROR) << "Frame size sanity check failed.  (expected "
+               << expected_frame_size << " got "
+               << wav_info_.frame_size << ")";
+    RunLoop::current()->Quit();

[jeffbrown, 2015/11/04 19:34:44]

FWIW, you might be better off making a single Validate function which checks
these things, logs errors, and returns true / false.  It'll be tidier than all
of these repeated quit blocks.

[johngro, 2015/11/05 00:25:16]

Agreed, Done.

+    return;
+  }
+
+  // Technically, there could be format specific member of the wave format
+  // chunk, or other riff chunks which could come after this, but for this demo,
+  // we only handle getting the 'data' chunk at this point.
+  RIFFChunkHeader data_hdr;
+  if (!BlockingRead(&data_hdr, sizeof(data_hdr))) {
+    LOG(ERROR) << "Failed to read data header!";
+    RunLoop::current()->Quit();
+    return;
+  }
+
+  if (data_hdr.four_cc != DATA_FOUR_CC) {
+    LOG(ERROR) << "Missing expected 'data' 4CC "
+               << "(expected 0x " << std::hex << DATA_FOUR_CC
+               << " got 0x"       << std::hex << data_hdr.four_cc
+               << ")";
+    RunLoop::current()->Quit();
+    return;
+  }
+
+  if ((data_hdr.length + sizeof(WAVHeader) + sizeof(RIFFChunkHeader))
+      != riff_hdr.length) {
+    LOG(ERROR) << "Header length sanity check failure ("
+               << data_hdr.length << " + "
+               << sizeof(WAVHeader) + sizeof(RIFFChunkHeader) << " != "
+               << riff_hdr.length << ")";
+    RunLoop::current()->Quit();
+    return;
+  }
+
+  // If the length of the data chunk is not a multiple of the frame size, log a
+  // warning and truncate the length.
+  uint16_t leftover;
+  payload_len_ = data_hdr.length;
+  leftover     = payload_len_ % wav_info_.frame_size;
+  if (leftover) {
+    LOG(WARNING) << "Data chunk length (" << payload_len_
+                 << ") not a multiple of frame size (" << wav_info_.frame_size
+                 << ")";
+    payload_len_ -= leftover;
+  }
+
+  LOG(INFO) << "Preparing to play...";
+  LOG(INFO) << "File : " << TEST_FILE;
+  LOG(INFO) << "Rate : " << wav_info_.frame_rate;
+  LOG(INFO) << "Chan : " << wav_info_.channel_count;
+  LOG(INFO) << "BPS  : " << wav_info_.bits_per_sample;
+
+  // Create the audio sink we will use to play this WAV file and start to
+  // configure it.
+  audio_server_->CreateTrack(GetProxy(&audio_track_));
+
+  LinearTransform::Ratio audio_rate(wav_info_.frame_rate, 1);
+  LinearTransform::Ratio local_rate(LocalDuration::period::num,
+                                    LocalDuration::period::den);
+  LinearTransform::Ratio tmp;
+  bool success = LinearTransform::Ratio::Compose(audio_rate, local_rate, &tmp);
+  DCHECK(success);
+
+  AudioTrackConfigurationPtr cfg;
+  cfg = AudioTrackConfiguration::New();
+  cfg->max_frames = USecToFrames(BUF_DEPTH_USEC);
+  cfg->audio_frame_ratio = tmp.numerator;
+  cfg->media_time_ratio  = tmp.denominator;
+
+  LpcmMediaTypeDetailsPtr pcm_cfg = LpcmMediaTypeDetails::New();
+  pcm_cfg->sample_format = (wav_info_.bits_per_sample == 8)
+                         ? LpcmSampleFormat::UNSIGNED_8
+                         : LpcmSampleFormat::SIGNED_16;
+  pcm_cfg->samples_per_frame = wav_info_.channel_count;
+  pcm_cfg->frames_per_second = wav_info_.frame_rate;
+
+  cfg->media_type = MediaType::New();
+  cfg->media_type->scheme = MediaTypeScheme::LPCM;
+  cfg->media_type->details = MediaTypeDetails::New();
+  cfg->media_type->details->set_lpcm(pcm_cfg.Pass());
+
+
+  audio_track_->Configure(cfg.Pass(),
+                          GetProxy(&media_pipe_),
+                          [this](MediaResult res) {
+                            this->OnAudioConfigured(res);

[jeffbrown, 2015/11/04 19:34:44]

Why can't we just send the rate control request immediately here?  We don't need
to wait for the callback.

Be sure to watch for connection errors on the audio_track_.

[johngro, 2015/11/05 00:25:16]

will change, I'm going to finish responses to initial feedback and push a new CL
before coming back and restructuring this.  Watching for connections errors is
something which should be done no matter what, but since I do not close the pipe
from the other end (and will not do until there is a good way to propagate
diagnostics), its not something which should ever fire.

+                          });
+}
+
+void PlayWAVApp::OnAudioConfigured(MediaResult res) {
+  if (res != MediaResult::OK) {
+    LOG(ERROR) << "Failed to configure audio track (res = " << res << ")";
+    RunLoop::current()->Quit();
+    return;
+  }
+
+  // Grab the rate control interface for our audio renderer.
+  audio_track_->GetRateControl(GetProxy(&rate_control_),
+                              [this](MediaResult res) {
+                                this->OnHasRateControl(res);

[jeffbrown, 2015/11/04 19:34:44]

Likewise, no need to wait for the callback before we can start using the pipe.

[johngro, 2015/11/05 00:25:16]

Acknowledged.

+                              });
+}
+
+void PlayWAVApp::OnHasRateControl(MediaResult res) {
+  if (res != MediaResult::OK) {
+    LOG(ERROR) << "Failed to fetch rate control interface "
+               << "(res = " << res << ")";
+    RunLoop::current()->Quit();
+    return;
+  }
+
+  // Set up our media pipe helper, configure its callback and water marks to
+  // kick off the playback process.
+  audio_pipe_.reset(new CircularBufferMediaPipeAdapter(media_pipe_.Pass()));
+  audio_pipe_->SetWatermarks(USecToBytes(BUF_HI_WATER_USEC),
+                             USecToBytes(BUF_LO_WATER_USEC));
+  audio_pipe_->SetSignalCallback(
+      [this](MediaResult res) -> bool {
+        return OnNeedsData(res);
+      });
+}
+
+bool PlayWAVApp::OnNeedsData(MediaResult res) {
+  if (res != MediaResult::OK) {
+    LOG(ERROR) << "Error during playback!  (res = " << res << ")";
+    RunLoop::current()->Quit();
+    return false;
+  }
+
+  uint64_t bytes = USecToBytes(CHUNK_SIZE_USEC);
+  if (bytes > payload_len_) {
+    bytes = payload_len_;
+  }
+
+  res = audio_pipe_->CreateMediaPacket(bytes, false, &audio_packet_);
+  if (res != MediaResult::OK) {
+    LOG(ERROR) << "Failed to create " << bytes << " byte media packet!  "
+               << "(res = " << res << ")";
+    RunLoop::current()->Quit();
+    return false;
+  }
+
+  if (!sent_first_packet_) {
+    DCHECK(audio_packet_.packet());
+    audio_packet_.packet()->pts = 0;
+    sent_first_packet_ = true;
+  }
+
+  for (size_t i = 0; i < AudioPacket::kMaxRegions; ++i) {
+    if (audio_packet_.data(i)) {
+      DCHECK(audio_packet_.length(i));
+      DCHECK(audio_packet_.length(i) <= payload_len_);
+
+      if (!BlockingRead(audio_packet_.data(i),
+                        audio_packet_.length(i))) {
+        LOG(ERROR) << "Failed to read source, shutting down...";
+        RunLoop::current()->Quit();
+        return false;
+      }
+
+      payload_len_ -= audio_packet_.length(i);
+    }
+  }
+
+  if (payload_len_) {
+    res = audio_pipe_->SendMediaPacket(&audio_packet_);
+  } else {
+    res = audio_pipe_->SendMediaPacket(&audio_packet_, playout_complete_cbk_);
+  }
+
+  if (res != MediaResult::OK) {
+    LOG(ERROR) << "Failed to send media packet!  "
+               << "(res = " << res << ")";
+    RunLoop::current()->Quit();
+    return false;
+  }
+
+  if (!clock_started_ && (audio_pipe_->AboveHiWater() || !payload_len_)) {
+    LocalTime sched = LocalClock::now() + local_time::from_msec(50);
+    rate_control_->SetRateAtTargetTime(1, 1, sched.time_since_epoch().count());
+    clock_started_ = true;
+  }
+
+  return (payload_len_ != 0);
+}
+
+void PlayWAVApp::OnPlayoutComplete(MediaResult res) {
+  DCHECK(!audio_pipe_->GetPending());
+  RunLoop::current()->Quit();
+}
+
+}  // namespace examples
+}  // namespace audio
+}  // namespace media
+}  // namespace mojo
+
+MojoResult MojoMain(MojoHandle app_request) {
+  mojo::ApplicationRunner runner(new mojo::media::audio::examples::PlayWAVApp);
+  return runner.Run(app_request);
+}