Render inband text tracks in the media pipeline

media/filters/text_decoder_impl.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/filters/text_decoder_impl.h"
+
+#include "base/callback_helpers.h"
+#include "media/base/bind_to_loop.h"
+#include "media/base/decoder_buffer.h"
+#include "media/base/demuxer.h"
+#include "media/base/text_cue.h"
+
+namespace media {
+
+TextDecoderImpl::TextDecoderImpl(
+    const scoped_refptr<base::MessageLoopProxy>& message_loop)
+    : message_loop_(message_loop),
+      weak_factory_(this) {
+}
+
+TextDecoderImpl::~TextDecoderImpl() {
+}
+
+void TextDecoderImpl::Initialize() {
+  DCHECK(message_loop_->BelongsToCurrentThread());
+  weak_this_ = weak_factory_.GetWeakPtr();
+}
+
+void TextDecoderImpl::Read(DemuxerStream* stream, const ReadCB& read_cb) {
+  DCHECK(message_loop_->BelongsToCurrentThread());
+  DCHECK(!read_cb.is_null());
+
+  ReadCB& cb = read_callbacks_[stream];
+  CHECK(cb.is_null()) << "Overlapping decodes are not supported.";
+
+  cb = BindToCurrentLoop(read_cb);
+
+  stream->Read(base::Bind(
+      &TextDecoderImpl::BufferReady, weak_this_, stream));
+}
+
+void TextDecoderImpl::BufferReady(
+    DemuxerStream* stream,
+    DemuxerStream::Status status,
+    const scoped_refptr<DecoderBuffer>& input) {
+  DCHECK(message_loop_->BelongsToCurrentThread());
+
+  ReadCB& read_cb = read_callbacks_[stream];
+  DCHECK(!read_cb.is_null());
+
+  if (status == DemuxerStream::kAborted) {
+    DCHECK(!input.get());
+    base::ResetAndReturn(&read_cb).Run(stream, NULL);
+    return;
+  }
+
+  if (input->end_of_stream()) {
+    base::ResetAndReturn(&read_cb).Run(stream, NULL);
+    return;
+  }
+
+  DCHECK_EQ(status, DemuxerStream::kOk);
+  DCHECK(input.get());
+  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));
+
+  base::ResetAndReturn(&read_cb).Run(stream, text_cue);
+}
+
+}  // namespace media