在iOS 5中使用AVFoundation设置最大帧速率 [英] Set maximum frame rate with AVFoundation in iOS 5

问题描述

我相信这曾经用 captureOutput.minFrameDuration 完成。但是，这在iOS 5中已被弃用。

I believe this used to be done with captureOutput.minFrameDuration. However, this is deprecated in iOS 5.

相反，我显然需要使用 AVCaptureConnection 的 video.minFrameDuration 。所以我有输入，我的输出，我将它们添加到捕获会话 - 我在哪里可以访问捕获连接？我认为它是由会话创建的，但在哪里？

Instead I apparently need to use AVCaptureConnection's video.minFrameDuration. So I have my input, my output, I add them both the the capture session - where can I get access to the capture connection? I think it is created for me by the session, but where?

我可以尝试使用 addInputWithNoConnections 和 addOutputWithNoConnections 然后可能手动创建连接。但是，设置最大帧速率似乎有点麻烦。另外，Xcode抱怨这些方法不存在。

I could try adding the I/O using addInputWithNoConnections and addOutputWithNoConnections and then maybe creating the connection manually. But this seems like a bit of hassle just to set a maximum frame rate. Plus, Xcode complains that these methods don't exist.

推荐答案

克里斯，我想我已经解决了这个问题：

Chris, I think I have solved this problem:

（编辑 - 请参阅下面的Tomas Camin评论关于是否支持videoMinFrameDuration videoMaxFrameDuration的正确方法，尽管以下代码在发布时工作正常）

以下行可以访问与 AVCaptureVideoDataOutput AVCaptureConnection 对象> object：

The line below gives access to the AVCaptureConnection object associated with the AVCaptureVideoDataOutput object:

AVCaptureConnection *conn = [output connectionWithMediaType:AVMediaTypeVideo];


CMTimeShow(conn.videoMinFrameDuration);
CMTimeShow(conn.videoMaxFrameDuration);

if (conn.isVideoMinFrameDurationSupported)
    conn.videoMinFrameDuration = CMTimeMake(1, CAPTURE_FRAMES_PER_SECOND);
if (conn.isVideoMaxFrameDurationSupported)
    conn.videoMaxFrameDuration = CMTimeMake(1, CAPTURE_FRAMES_PER_SECOND);

CMTimeShow(conn.videoMinFrameDuration);
CMTimeShow(conn.videoMaxFrameDuration);

如果您正在使用（我是）， didOutputSampleBuffer 委托，您可以确认传入代理的 fromConnection AVCaptureConnection *值中的视频帧速率已正确设置并由上述记住码。

If you're using (as I am), the didOutputSampleBuffer delegate, you can confirm that the video frame rate in the fromConnection AVCaptureConnection * value passed in to the delegate has been correctly set and "remembered" by the above code.

请注意，您需要设置 videoMinFrameDuration 和 videoMaxFrameDuration 以相同的值成功锁定帧速率 - 在iPhone 4s上测试时，设置min本身似乎不起作用。这似乎没有记录。

Note that you need to set both videoMinFrameDuration and videoMaxFrameDuration to the same value to successfully clamp the frame rate -- setting min on its own did not seem to work when testing on an iPhone 4s. This doesn't seem to be documented.

Josh

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