Media Galleries API Metadata: Add audio video metadata extractor.

chrome/common/extensions/api/media_galleries.idl

 // Copyright (c) 2012 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.
 
 // Use the <code>chrome.mediaGalleries</code> API to access media files (images,
 // video, audio) from the user's local disks (with the user's consent).
 namespace mediaGalleries {
 
   [inline_doc] enum GetMediaFileSystemsInteractivity {
     // Do not act interactively.
@@ skipping 51 matching lines @@
     // True if the device is currently available.
     boolean isAvailable;
   };
 
   callback MediaFileSystemsMetadataCallback =
       void (MediaFileSystemMetadata[] metadata);
 
   dictionary MediaMetadata {
     // The browser sniffed mime type.
     DOMString mimeType;
+    
+    // Defined for images and video. In pixels.
+    long? height;
+    long? width;
+    
+    // Defined for audio and video.
+    long? durationSeconds;

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

nit: Consider using a double since time in HTMLMediaElements are represented as
doubles. Also s/durationSeconds/duration/ to match the HTMLMediaElement field
that would have a equivalent value if you actually loaded the file.

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

Done.

+    
+    // FFmpeg-defined generic fields.

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

I don't think it is wise to expose these fields in terms of what FFmpeg returns.
These seem more like ID3 type fields so you should probably reference
appropriate parts of that spec for each one so these values are well defined.

Another reason to not bind this to FFmpeg is that FFmpeg isn't used on Android.

[Lei Zhang, 2014/01/03 23:00:15]

Chrome extensions and apps are not available on mobile platforms either, FWIW.

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

Comment might be misleading. FFmpeg inspired the tag names, but we could
implement this with an alternate backend also.

On 2014/01/03 19:14:04, acolwell wrote:

+    DOMString? album;
+    DOMString? artist;
+    DOMString? comment;
+    DOMString? copyright;
+    long? disc;
+    DOMString? genre;
+    DOMString? language;
+    DOMString? title;
+    long? track;
   };
 
   callback MediaMetadataCallback = void (MediaMetadata metadata);
 
   interface Functions {
     // Get the media galleries configured in this user agent. If none are
     // configured or available, the callback will receive an empty array.
     static void getMediaFileSystems(optional MediaFileSystemsDetails details,
                                     MediaFileSystemsCallback callback);
 
     // Get metadata about a specific media file system.
     [nocompile] static MediaFileSystemMetadata getMediaFileSystemMetadata(
         [instanceOf=DOMFileSystem] object mediaFileSystem);
 
     // Get metadata for all available media galleries.
     static void getAllMediaFileSystemMetadata(
         MediaFileSystemsMetadataCallback callback);
                 
     // Gets the media-specific metadata for a media file. This should work
     // for files in media galleries as well as other DOM filesystems.
     static void getMetadata([instanceOf=Blob] object mediaFile,
                             optional MediaMetadataOptions options,
                             MediaMetadataCallback callback);
   };
 
 };