找出Quicktime电影的编解码器 [英] Find out the Codec for a Quicktime Movie

问题描述

我一直想知道是否可以找到使用哪个编解码器解压缩Quicktime影片（例如h.264，motion jpeg。），最好使用 NSString 。我搜索了 Quicktime 和 QTKit api以及所有gettable属性，但均未成功，但我确信必须有一个

I´ve been wondering if it is possible to find out which Codec is used to Decompress a Quicktime Movie (like h.264, motion jpeg.. ), preferable as NSString. I searched through the Quicktime and QTKit api and all gettable attributes with no success, but I am sure there must be a way to do this, but how?

推荐答案

我认为您遇到了这个困难，因为您误解了Quicktime电影-问电影的编解码器是没有意义的，这就是为什么您没有在电影文档中找到它的原因。

I think you're having this difficulty because you're misunderstanding the nature of a Quicktime movie - it doesn't make sense to ask what the codec of a movie is, and that's why you're not finding it in the documentation for movies.

Quicktime电影是由轨道（例如视频轨道，音频轨道等）的集合组成的，每个轨道都引用一个或多个媒体（实际数据）。使用特定编解码器压缩的媒体。例如，通常电影会具有视频轨道和音频轨道，每个轨道都将使用不同的编解码器（可能是h.264和aac）进行压缩-因此，没有一个编解码器

Quicktime movies are made of a collection of tracks (eg. video track, audio track etc.) and each track references one or more media (the actual data). It's the media that is compressed with a particular codec. Usually a movie will have a video track and an audio track, for instance, each of which will be compressed with a different codec (h.264 and aac maybe) - so there isn't one codec for the whole movie.

要找到用于压缩电影视频轨道的编解码器（听起来像您要执行的操作），您需要先获得一个从电影中引用该曲目，然后获得对该曲目媒体的引用，然后找出用于该媒体的编解码器。要获取有关如何存储特定媒体对象的样本的信息，您需要使用 getmediasampledescription 调用。

To find the codec used to compress the video track of the movie (which sounds like what you're trying to do) you need to first get a reference to that track from the movie, then get a reference to the media of that track, then find out the codec used for that media. To get information about how the samples for a particular media object are stored you need to use the getmediasampledescription call.

如果您使用的是QTKit，请通过调用[media quicktimeMedia]获取C级媒体参考-然后您可以将其传递给getmediasampledescription以获得您所需要的信息寻找-编解码器4位标识符位于返回的示例说明的cType字段中。

If you're using QTKit, get the C-level media reference by calling [media quicktimeMedia] - then you can pass this to getmediasampledescription to get the info you're looking for - the codec 4-digit identifer is in the cType field of the returned sample description.

此苹果支持列表中有一些示例代码：

There's a bit of sample code in this apple support list posting :

http ：//lists.apple.com/archives/cocoa-dev/2005//Aug/msg00556.html

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