如何在 Objective C/Cocoa 中获取 QuickTime 视频的编解码器信息？ （没有 FFMPEG）

Question

您好，感谢您抽出时间， 我正在创建一个应用程序，可以移动视频文件以供其他应用程序处理。过去，我在 ruby​​ 中使用 mediainfo 和 ffmpeg 来获取每个文件的编解码器信息。然而，我想将所有这些转移到一个漂亮的可可应用程序中。我搜索了又搜索，但仍然找不到如何执行此操作的解决方案（不使用 ffmpeg）。我基本上正在寻找与您在 QuickTime 视频检查器窗口（Apple + i）中获得的完全相同的信息。 任何帮助将不胜感激，示例代码，更是如此。 谢谢。

Answer 1

您可以使用 Spotlight 查询 (NSMetadataQuery)，如 mdls 命令：

> mdls ~/Music/iTunes/iTunes\ Media/iTunes\ U/WWDC\ 2011\ Session\ Videos\ -\ HD/1-01\ Apple\ Platforms\ Kickoff.m4v 
kMDItemAudioBitRate            = 103
kMDItemAudioChannelCount       = 2
kMDItemCodecs                  = (
    AAC,
    "H.264"
)
kMDItemContentCreationDate     = 2011-07-01 15:49:56 +0000
kMDItemContentModificationDate = 2011-07-01 16:13:39 +0000
kMDItemContentType             = "com.apple.m4v-video"
kMDItemContentTypeTree         = (
    "com.apple.m4v-video",
    "public.movie",
    "public.audiovisual-content",
    "public.data",
    "public.item",
    "public.content"
)
kMDItemDateAdded               = 2011-07-01 16:13:39 +0000
kMDItemDisplayName             = "1-01 Apple Platforms Kickoff.m4v"
kMDItemDurationSeconds         = 2787.754421087755
kMDItemFSContentChangeDate     = 2011-07-01 16:13:39 +0000
kMDItemFSCreationDate          = 2011-07-01 15:49:56 +0000
kMDItemFSCreatorCode           = "hook"
kMDItemFSFinderFlags           = 0
kMDItemFSHasCustomIcon         = 0
kMDItemFSInvisible             = 0
kMDItemFSIsExtensionHidden     = 0
kMDItemFSIsStationery          = 0
kMDItemFSLabel                 = 0
kMDItemFSName                  = "1-01 Apple Platforms Kickoff.m4v
kMDItemFSNodeCount             = 1147843844
kMDItemFSOwnerGroupID          = 20
kMDItemFSOwnerUserID           = 502
kMDItemFSSize                  = 1147843844
kMDItemFSTypeCode              = ""
kMDItemKind                    = "Video Media"
kMDItemLogicalSize             = 1147843844
kMDItemMediaTypes              = (
    Sound,
    Video
)
kMDItemPhysicalSize            = 1147846656
kMDItemPixelHeight             = 540
kMDItemPixelWidth              = 958
kMDItemProfileName             = "HD (1-1-1)"
kMDItemStreamable              = 0
kMDItemTotalBitRate            = 3287
kMDItemVideoBitRate            = 3184

或者您可以检查 AVFoundation 框架。

示例代码：

 -(NSDictionary *) metadataForFileAtPath:(NSString *) path {
    NSURL *url = [[[NSURL alloc] initFileURLWithPath:path] autorelease];

    MDItemRef itemRef = MDItemCreateWithURL(NULL, (CFURLRef)url);
    NSArray *attributeNames = (NSArray *)MDItemCopyAttributeNames(itemRef);
    NSDictionary *attributes = (NSDictionary *) MDItemCopyAttributes(itemRef, (CFArrayRef) attributeNames);
    CFRelease(itemRef);

    // probably it is leaking memory (attributeNames and attributes), better check with Instruments

    return attributes;
}