Render inband text tracks in the media pipeline

media/base/text_renderer.cc

+// Copyright (c) 2013 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/base/text_renderer.h"
+
+#include "base/bind.h"
+#include "base/callback_helpers.h"
+#include "base/logging.h"
+#include "base/message_loop/message_loop_proxy.h"
+#include "base/stl_util.h"
+#include "media/base/bind_to_loop.h"
+#include "media/base/decoder_buffer.h"
+#include "media/base/demuxer.h"
+#include "media/base/demuxer_stream.h"
+#include "media/base/text_cue.h"
+
+namespace media {
+
+TextRenderer::TextRenderer(
+    const scoped_refptr<base::MessageLoopProxy>& message_loop,
+    const AddTextTrackCB& add_text_track_cb)
+    : message_loop_(message_loop),
+      weak_factory_(this),
+      add_text_track_cb_(add_text_track_cb),
+      state_(kUninitialized),
+      pending_read_count_(0),
+      pending_eos_count_(0) {
+}
+
+TextRenderer::~TextRenderer() {
+  DCHECK(state_ == kUninitialized ||
+         state_ == kStopped) << "state_ " << state_;
+  DCHECK_EQ(pending_read_count_, 0);
+
+  STLDeleteValues(&text_track_map_);
+}
+
+void TextRenderer::Initialize(const base::Closure& ended_cb) {
+  DCHECK(message_loop_->BelongsToCurrentThread());
+  DCHECK(!ended_cb.is_null());
+  DCHECK_EQ(kUninitialized, state_)  << "state_ " << state_;
+  DCHECK(read_state_.empty());
+  DCHECK_EQ(pending_read_count_, 0);
+  DCHECK_EQ(pending_eos_count_, 0);
+  DCHECK(ended_cb_.is_null());
+
+  weak_this_ = weak_factory_.GetWeakPtr();
+  ended_cb_ = ended_cb;
+  state_ = kPaused;
+}
+
+void TextRenderer::Play(const base::Closure& callback) {
+  DCHECK(message_loop_->BelongsToCurrentThread());
+  DCHECK_EQ(state_, kPaused) << "state_ " << state_;
+
+  state_ = kPlaying;
+  callback.Run();

[acolwell GONE FROM CHROMIUM, 2013/10/14 20:42:24]

It is safer to run the callback at the end of the method just to avoid any
potential reentrancy issues. Running it at the end is also a better reflection
that you are actually done starting playback.

[Matthew Heaney (Chromium), 2013/10/17 05:46:44]

Done.

[Matthew Heaney (Chromium), 2013/10/17 05:46:44]

Done.

+
+  for (ReadStateMap::iterator itr = read_state_.begin();
+       itr != read_state_.end(); ++itr) {
+    if (itr->second == kReadPending) {
+      DCHECK_GT(pending_read_count_, 0);
+      continue;
+    }
+
+    itr->second = kReadPending;
+    ++pending_read_count_;
+
+  DemuxerStream* const stream = itr->first;
+  stream->Read(base::Bind(&TextRenderer::BufferReady,
+                          weak_this_,
+                          stream));
+  }
+}
+
+void TextRenderer::Pause(const base::Closure& callback) {
+  DCHECK(message_loop_->BelongsToCurrentThread());
+  DCHECK(state_ == kPlaying || state_ == kEnded) << "state_ " << state_;
+  DCHECK_GE(pending_read_count_, 0);
+  pause_cb_ = callback;
+
+  if (pending_read_count_ == 0) {
+    state_ = kPaused;
+    base::ResetAndReturn(&pause_cb_).Run();
+    return;
+  }
+
+  state_ = kPausePending;
+}
+
+void TextRenderer::Flush(const base::Closure& callback) {
+  DCHECK(message_loop_->BelongsToCurrentThread());
+  DCHECK_EQ(pending_read_count_, 0);
+  DCHECK(state_ == kPaused || state_ == kEnded) << "state_ " << state_;
+
+  pending_eos_count_ = read_state_.size();
+
+  callback.Run();
+}
+
+void TextRenderer::Stop(const base::Closure& cb) {
+  DCHECK(message_loop_->BelongsToCurrentThread());
+  DCHECK(!cb.is_null());
+  DCHECK(state_ == kPlaying ||
+         state_ == kPaused ||

[acolwell GONE FROM CHROMIUM, 2013/10/14 20:42:24]

I'm pretty sure you need to add kPausePending to this list. I'm pretty sure the
pipeline won't wait for Pause() to complete before calling Stop(). 

[Matthew Heaney (Chromium), 2013/10/17 05:46:44]

Done.

+         state_ == kEnded) << "state_ " << state_;
+  DCHECK_GE(pending_read_count_, 0);
+
+  stop_cb_ = cb;
+
+  if (pending_read_count_ == 0) {
+    state_ = kStopped;
+    base::ResetAndReturn(&stop_cb_).Run();
+    return;
+  }
+
+  state_ = kStopPending;
+}
+
+void TextRenderer::AddTextStream(DemuxerStream* text_stream,
+                                 TextKind kind,
+                                 const std::string& label,
+                                 const std::string& language) {
+  DCHECK(message_loop_->BelongsToCurrentThread());
+  DCHECK(state_ != kUninitialized &&
+         state_ != kStopped) << "state_ " << state_;
+
+  media::AddTextTrackDoneCB done_cb =
+      media::BindToLoop(message_loop_,
+                        base::Bind(&TextRenderer::OnAddTextTrackDone,
+                                   weak_this_,
+                                   text_stream));
+
+  add_text_track_cb_.Run(kind, label, language, done_cb);
+}
+
+void TextRenderer::OnAddTextTrackDone(DemuxerStream* text_stream,
+                                      scoped_ptr<TextTrack> text_track) {
+  DCHECK(message_loop_->BelongsToCurrentThread());
+  DCHECK(state_ != kUninitialized &&
+         state_ != kStopped) << "state_ " << state_;

[acolwell GONE FROM CHROMIUM, 2013/10/14 20:42:24]

I believe it might be possible for state_ to be in kStopping or kStopped when
this is run. You might just want to return early in those cases.

[Matthew Heaney (Chromium), 2013/10/17 05:46:44]

Done.

+
+  text_track_map_[text_stream] = text_track.release();
+
+  ++pending_eos_count_;
+
+  if (state_ != kPlaying) {
+    read_state_[text_stream] = kReadIdle;
+  } else {
+    read_state_[text_stream] = kReadPending;
+    ++pending_read_count_;
+
+    text_stream->Read(base::Bind(&TextRenderer::BufferReady,
+                                 weak_this_,
+                                 text_stream));
+  }
+}
+
+bool TextRenderer::HasTracks() const {
+  DCHECK(message_loop_->BelongsToCurrentThread());
+  return !text_track_map_.empty();
+}
+
+void TextRenderer::BufferReady(
+    DemuxerStream* stream,
+    DemuxerStream::Status status,
+    const scoped_refptr<DecoderBuffer>& input) {
+  DCHECK(message_loop_->BelongsToCurrentThread());
+

[acolwell GONE FROM CHROMIUM, 2013/10/14 20:42:24]

nit: DCHECK_NE(status, DemuxerStream::kConfigChanged);

[Matthew Heaney (Chromium), 2013/10/17 05:46:44]

Done.

+  if (status == DemuxerStream::kAborted) {
+    DCHECK(!input.get());
+    CueReady(stream, NULL);

[acolwell GONE FROM CHROMIUM, 2013/10/14 20:42:24]

I think there is a bug here. Aborted reads should not be able to trigger
ended_cb_ to run.

[Matthew Heaney (Chromium), 2013/10/17 05:46:44]

Done.

+    return;
+  }
+
+  if (input->end_of_stream()) {
+    CueReady(stream, NULL);
+    return;
+  }
+
+  DCHECK_EQ(status, DemuxerStream::kOk);
+  DCHECK(input.get());

[acolwell GONE FROM CHROMIUM, 2013/10/14 20:42:24]

nit: Remove since you would have NPE above it this wasn't true.

[Matthew Heaney (Chromium), 2013/10/17 05:46:44]

Done.

+  DCHECK_GE(input->side_data_size(), 2);
+
+  // The side data contains both the cue id and cue settings,
+  // each terminated with a NUL.
+  const char* id_ptr = reinterpret_cast<const char*>(input->side_data());
+  size_t id_len = strlen(id_ptr);
+  std::string id(id_ptr, id_len);
+
+  const char* settings_ptr = id_ptr + id_len + 1;
+  size_t settings_len = strlen(settings_ptr);
+  std::string settings(settings_ptr, settings_len);
+
+  // The cue payload is stored in the data-part of the input buffer.
+  std::string text(input->data(), input->data() + input->data_size());
+
+  scoped_refptr<TextCue> text_cue(
+      new TextCue(input->timestamp(),
+                  input->duration(),
+                  id,
+                  settings,
+                  text));
+
+  CueReady(stream, text_cue);
+}
+
+void TextRenderer::CueReady(
+    DemuxerStream* text_stream,
+    const scoped_refptr<TextCue>& text_cue) {
+  DCHECK(message_loop_->BelongsToCurrentThread());
+  DCHECK(state_ != kUninitialized &&
+         state_ != kStopped) << "state_ " << state_;
+  DCHECK_GT(pending_read_count_, 0);
+  DCHECK_GT(pending_eos_count_, 0);
+  DCHECK_EQ(read_state_[text_stream], kReadPending);
+
+  --pending_read_count_;
+  read_state_[text_stream] = kReadIdle;
+
+  switch (state_) {
+    case kPlaying:
+    case kPausePending:
+      if (text_cue)
+        break;
+
+      // A NULL buffer means that we have reached EOS (or there's an error).
+
+      --pending_eos_count_;
+
+      if (pending_eos_count_ > 0)
+        return;
+
+      if (state_ == kPausePending)
+        pause_cb_.Run();
+
+      state_ = kEnded;
+      ended_cb_.Run();
+
+      return;
+
+    case kStopPending:
+      if (pending_read_count_ == 0) {
+        state_ = kStopped;
+        stop_cb_.Run();
+      }
+
+      return;
+
+    case kPaused:
+    case kStopped:
+    case kUninitialized:
+      NOTREACHED();
+      return;
+  }
+
+  TextTrackMap::iterator it = text_track_map_.find(text_stream);
+  DCHECK(it != text_track_map_.end());
+
+  media::TextTrack* text_track = it->second;
+  DCHECK_NE(text_track, static_cast<media::TextTrack*>(NULL));

[acolwell GONE FROM CHROMIUM, 2013/10/14 20:42:24]

nit: Use DCHECK(text_track) instead.

[Matthew Heaney (Chromium), 2013/10/17 05:46:44]

Done.

+
+  base::TimeDelta start = text_cue->timestamp();
+  base::TimeDelta end = start + text_cue->duration();
+
+  text_track->addWebVTTCue(start, end,
+                            text_cue->id(),
+                            text_cue->text(),
+                            text_cue->settings());
+
+  if (state_ == kPlaying) {
+    read_state_[text_stream] = kReadPending;
+    ++pending_read_count_;
+    text_stream->Read(base::Bind(&TextRenderer::BufferReady,
+                                 weak_this_,
+                                 text_stream));

[acolwell GONE FROM CHROMIUM, 2013/10/14 20:42:24]

nit: return early & drop else

[Matthew Heaney (Chromium), 2013/10/17 05:46:44]

Done.

+  } else if (pending_read_count_ == 0) {
+      state_ = kPaused;
+      pause_cb_.Run();
+  }
+}
+
+}  // namespace media