Media Galleries API Metadata: Add audio video metadata extractor.

media/base/audio_video_metadata_extractor.cc

+// Copyright 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/audio_video_metadata_extractor.h"
+
+#include <map>
+
+#include "base/bind.h"
+#include "base/strings/string_util.h"
+#include "base/time/time.h"
+#include "media/ffmpeg/ffmpeg_common.h"
+#include "media/filters/blocking_url_protocol.h"
+#include "media/filters/ffmpeg_glue.h"
+
+namespace media {
+
+namespace {
+
+static void OnError(bool* called) {
+  *called = false;
+}
+
+std::map<std::string, std::string> ExtractAVMetadata(AVDictionary* metadata) {
+  DCHECK(metadata);
+
+  std::map<std::string, std::string> tags;
+
+  AVDictionaryEntry *tag = NULL;
+  while ((tag = av_dict_get(metadata, "", tag, AV_DICT_IGNORE_SUFFIX))) {
+    std::string key = tag->key;
+    StringToLowerASCII(&key);
+    tags[key] = std::string(tag->value);
+  }
+
+  return tags;
+}
+
+}  // namespace
+
+AudioVideoMetadataExtractor::AudioVideoMetadataExtractor(DataSource* source)
+    : source_(source),
+      extracted_(false),
+      duration_(-1),
+      width_(0),
+      height_(0) {
+}
+
+AudioVideoMetadataExtractor::~AudioVideoMetadataExtractor() {
+}
+
+bool AudioVideoMetadataExtractor::Extract() {
+  bool read_ok = true;
+  media::BlockingUrlProtocol protocol(source_, base::Bind(&OnError, &read_ok));
+  media::FFmpegGlue glue(&protocol);
+  AVFormatContext* format_context = glue.format_context();
+
+  if (!glue.OpenContext())
+    return false;
+
+  if (!read_ok)
+    return false;
+
+  if (!format_context->iformat)
+    return false;
+
+  if (avformat_find_stream_info(format_context, NULL) < 0)
+    return false;
+
+  format_ = format_context->iformat->name;
+
+  if (format_context->duration != AV_NOPTS_VALUE)
+      duration_ = format_context->duration / AV_TIME_BASE;
+
+  if (format_context->metadata)
+    tags_ = ExtractAVMetadata(format_context->metadata);
+
+  bool container_has_metadata = !tags_.empty();
+
+  for (unsigned int i = 0; i < format_context->nb_streams; ++i) {
+    AVStream* stream = format_context->streams[i];
+    if (!stream)
+      continue;
+
+    // Ignore attached pictures for metadata extraction.
+    if ((stream->disposition & AV_DISPOSITION_ATTACHED_PIC) != 0)
+      continue;
+
+    // If the container does not have metadata, take the metadata from the
+    // stream with the most tags. This is needed for containers that attach
+    // metadata to contained streams instead the container itself, like OGG.

[acolwell GONE FROM CHROMIUM, 2014/01/03 19:14:04]

This seems brittle. How about just taking the first value for each property you
are looking for? At least that would allow you to catch metadata that is
sprinkled across multiple tracks.

[tommycli, 2014/01/03 23:08:36]

Done.

+    if (!container_has_metadata && stream->metadata) {
+      std::map<std::string, std::string> stream_tags =
+          ExtractAVMetadata(stream->metadata);
+      if (stream_tags.size() > tags_.size())
+        tags_ = stream_tags;
+    }
+
+    if (!stream->codec)
+      continue;
+
+    // Extract dimensions of largest stream that's not an attached picture.
+    if (stream->codec->width > width_ && stream->codec->height > height_) {
+      width_ = stream->codec->width;
+      height_ = stream->codec->height;
+    }
+  }
+
+  extracted_ = true;
+  return true;
+}
+
+const std::map<std::string, std::string>&
+AudioVideoMetadataExtractor::GetTags() {
+  DCHECK(extracted_);
+  return tags_;
+}
+
+const std::string& AudioVideoMetadataExtractor::GetFormat() {
+  DCHECK(extracted_);
+  return format_;
+}
+
+int AudioVideoMetadataExtractor::GetDurationSeconds() {
+  DCHECK(extracted_);
+  return duration_;
+}
+
+int AudioVideoMetadataExtractor::GetWidth() {
+  DCHECK(extracted_);
+  return width_;
+}
+
+int AudioVideoMetadataExtractor::GetHeight() {
+  DCHECK(extracted_);
+  return height_;
+}
+
+}  // namespace media