Media Galleries API Metadata: Add audio video metadata extractor.

media/base/audio_video_metadata_extractor.cc

+// Copyright 2014 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>

[Lei Zhang, 2014/01/07 21:44:25]

nit: remove

[tommycli, 2014/01/07 23:12:36]

Done.

+
+#include "base/bind.h"
+#include "base/strings/string_number_conversions.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) {

[Lei Zhang, 2014/01/07 21:44:25]

nit: no need for static

[Lei Zhang, 2014/01/07 21:44:25]

Isn't |succeeded| more clear than |called| ?

[tommycli, 2014/01/07 23:12:36]

Done.

[tommycli, 2014/01/07 23:12:36]

Done.

+  *called = false;
+}
+
+// Returns true if the |expected_key| matches |key_lower|.
+bool ExtractString(AVDictionaryEntry* tag, const std::string& key_lower,
+                   const std::string& expected_key, std::string* destination) {
+  if (key_lower != expected_key)
+    return false;
+
+  if (destination->empty())
+    *destination = tag->value;
+
+  return true;
+}
+
+// Returns true if the |expected_key| matches |key_lower|.
+bool ExtractInt(AVDictionaryEntry* tag, const std::string& key_lower,
+                const std::string& expected_key, int* destination) {
+  if (key_lower != expected_key)
+    return false;
+
+  int temporary = -1;
+  if (base::StringToInt(tag->value, &temporary) && temporary >= 0 &&
+      *destination < 0) {

[Lei Zhang, 2014/01/07 21:44:25]

it's cheaper to check *dest first before doing the StringToInt conversion.

[tommycli, 2014/01/07 23:12:36]

Done.

+    *destination = temporary;
+  }
+
+  return true;
+}
+
+}  // namespace
+
+AudioVideoMetadataExtractor::AudioVideoMetadataExtractor()
+    : extracted_(false),
+      duration_(-1),
+      width_(-1),
+      height_(-1),
+      disc_(-1),
+      track_(-1) {
+}
+
+AudioVideoMetadataExtractor::~AudioVideoMetadataExtractor() {
+}
+
+bool AudioVideoMetadataExtractor::Extract(media::DataSource* source) {
+  DCHECK(!extracted_);
+
+  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;
+
+  if (format_context->duration != AV_NOPTS_VALUE)
+    duration_ = static_cast<double>(format_context->duration) / AV_TIME_BASE;
+
+  ExtractDictionary(format_context->metadata);
+
+  for (unsigned int i = 0; i < format_context->nb_streams; ++i) {

[Lei Zhang, 2014/01/07 21:44:25]

Isn't |format_context->nb_streams| an int, and there by |i| should be as well?

[tommycli, 2014/01/07 23:12:36]

I believe nb_streams is an unsigned int.

+    AVStream* stream = format_context->streams[i];
+    if (!stream)
+      continue;
+
+    // Ignore attached pictures for metadata extraction.
+    if ((stream->disposition & AV_DISPOSITION_ATTACHED_PIC) != 0)
+      continue;
+
+    // Extract dictionary from streams also. Needed for containers that attach
+    // metadata to contained streams instead the container itself, like OGG.
+    ExtractDictionary(stream->metadata);
+
+    if (!stream->codec)
+      continue;
+
+    // Extract dimensions of largest stream that's not an attached picture.
+    if (stream->codec->width > 0 && stream->codec->width > width_ &&
+        stream->codec->height > 0 && stream->codec->height > height_) {
+      width_ = stream->codec->width;
+      height_ = stream->codec->height;
+    }
+  }
+
+  extracted_ = true;
+  return true;
+}
+
+double AudioVideoMetadataExtractor::duration() const {
+  DCHECK(extracted_);
+  return duration_;
+}
+
+int AudioVideoMetadataExtractor::width() const {
+  DCHECK(extracted_);
+  return width_;
+}
+
+int AudioVideoMetadataExtractor::height() const {
+  DCHECK(extracted_);
+  return height_;
+}
+
+const std::string& AudioVideoMetadataExtractor::album() const {
+  DCHECK(extracted_);
+  return album_;
+}
+
+const std::string& AudioVideoMetadataExtractor::artist() const {
+  DCHECK(extracted_);
+  return artist_;
+}
+
+const std::string& AudioVideoMetadataExtractor::comment() const {
+  DCHECK(extracted_);
+  return comment_;
+}
+
+const std::string& AudioVideoMetadataExtractor::copyright() const {
+  DCHECK(extracted_);
+  return copyright_;
+}
+
+const std::string& AudioVideoMetadataExtractor::date() const {
+  DCHECK(extracted_);
+  return date_;
+}
+
+int AudioVideoMetadataExtractor::disc() const {
+  DCHECK(extracted_);
+  return disc_;
+}
+
+const std::string& AudioVideoMetadataExtractor::encoder() const {
+  DCHECK(extracted_);
+  return encoder_;
+}
+
+const std::string& AudioVideoMetadataExtractor::encoded_by() const {
+  DCHECK(extracted_);
+  return encoded_by_;
+}
+
+const std::string& AudioVideoMetadataExtractor::genre() const {
+  DCHECK(extracted_);
+  return genre_;
+}
+
+const std::string& AudioVideoMetadataExtractor::language() const {
+  DCHECK(extracted_);
+  return language_;
+}
+
+const std::string& AudioVideoMetadataExtractor::title() const {
+  DCHECK(extracted_);
+  return title_;
+}
+
+int AudioVideoMetadataExtractor::track() const {
+  DCHECK(extracted_);
+  return track_;
+}
+
+void AudioVideoMetadataExtractor::ExtractDictionary(AVDictionary* metadata) {
+  if (!metadata)
+    return;
+
+  AVDictionaryEntry* tag = NULL;
+  while ((tag = av_dict_get(metadata, "", tag, AV_DICT_IGNORE_SUFFIX))) {
+    std::string key = tag->key;
+    StringToLowerASCII(&key);

[Lei Zhang, 2014/01/07 21:44:25]

Probably better to do this in ExtractString(), rather than require the passed in
key to be lowercase. You can also use LowerCaseEqualsASCII() to avoid the
conversion.

[tommycli, 2014/01/07 23:12:36]

Done.

+
+    // Try extracting all the defined keys.
+    if (ExtractString(tag, key, "album", &album_)) continue;
+    if (ExtractString(tag, key, "artist", &artist_)) continue;
+    if (ExtractString(tag, key, "comment", &comment_)) continue;
+    if (ExtractString(tag, key, "copyright", &copyright_)) continue;
+    if (ExtractString(tag, key, "date", &date_)) continue;
+    if (ExtractInt(tag, key, "disc", &disc_)) continue;
+    if (ExtractString(tag, key, "encoder", &encoder_)) continue;
+    if (ExtractString(tag, key, "encoded_by", &encoded_by_)) continue;
+    if (ExtractString(tag, key, "genre", &genre_)) continue;
+    if (ExtractString(tag, key, "language", &language_)) continue;
+    if (ExtractString(tag, key, "title", &title_)) continue;
+    if (ExtractInt(tag, key, "track", &track_)) continue;
+  }
+}
+
+}  // namespace media