AVFileCaptureOutput:不以240 fps录制 [英] AVFileCaptureOutput: Not recording at 240 fps

问题描述

我似乎在将相机设置为以240 FPS录制时遇到问题，但是由于某种原因，输出文件仅为30 FPS.

I seem to be having a problem where I am setting the camera to record at 240 FPS, but for some reason the output file is only 30 FPS.

这是我用于设置相机的代码(首先实例化):

Here is my code for setting up the camera (this is instantiated first):

class HFRCamera {
public:
    HFRCamera();

    AVCaptureDeviceInput *camera;
    AVCaptureDeviceInput *microphone;
    AVCaptureDevice *videoCam;
    AVCaptureDevice *audioInput;
    AVCaptureSession *capSession;

    void start();
    void config();
    void stop();

};

 HFRCamera::HFRCamera() {

     // Set up capture session and add video camera and microphone
    this->capSession = [[AVCaptureSession alloc] init];
    this->videoCam = [AVCaptureDevice    defaultDeviceWithMediaType:AVMediaTypeVideo];
     this->config();


}

void HFRCamera::start() {
    [this->capSession startRunning];
}

void HFRCamera::stop() {
    [this->capSession stopRunning];
}

void HFRCamera::config() {

const CGFloat desiredFPS = 240;
AVCaptureDeviceFormat *selectedFormat = nil;
AVFrameRateRange *frameRateRange = nil;
int32_t maxWidth = 0;

for (AVCaptureDeviceFormat *format in [this->videoCam formats]) {

    for (AVFrameRateRange *range in format.videoSupportedFrameRateRanges) {

        CMFormatDescriptionRef desc = format.formatDescription;
        CMVideoDimensions dimensions = CMVideoFormatDescriptionGetDimensions(desc);
        int32_t width = dimensions.width;

        if (range.minFrameRate <= desiredFPS && desiredFPS <= range.maxFrameRate && width >= maxWidth) {

            selectedFormat = format;
            frameRateRange = range;
            maxWidth = width;
        }
    }
}

if ([videoCam lockForConfiguration:nil]) {
    std::cout << "HERE\n";
    NSLog(@"selected format:%@", selectedFormat);
    this->videoCam.activeFormat = selectedFormat;
    this->videoCam.activeVideoMinFrameDuration = CMTimeMake(1, (int32_t)desiredFPS);
    this->videoCam.activeVideoMaxFrameDuration = CMTimeMake(1, (int32_t)desiredFPS);
    [this->videoCam unlockForConfiguration];

    NSLog(@"%s AVCaptureDevice: %@", __PRETTY_FUNCTION__, selectedFormat);
}



if (this->videoCam) {
    NSError *err;
    this->camera = [AVCaptureDeviceInput deviceInputWithDevice:this->videoCam error:&err];

    if (!err) {
        if ([this->capSession canAddInput:this->camera])
            [this->capSession addInput:this->camera];
        else
            NSLog(@"Could not add video input.");
    } else
        NSLog(@"Could not create video input");
} else {
    NSLog(@"Could not create video capture device.");
}

this->audioInput = [AVCaptureDevice defaultDeviceWithMediaType:AVMediaTypeAudio];
NSError *err = nil;
this->microphone = [AVCaptureDeviceInput deviceInputWithDevice:this->audioInput error:&err];
if (this->microphone)
    [this->capSession addInput:this->microphone];

// Configure camera
[this->capSession setSessionPreset:AVCaptureSessionPresetHigh];

}

最后，在ViewController中设置AVCameraFileOutput:

And finally, setting up the AVCameraFileOutput in ViewController:

// Configure the movie file output
self.movieFile = [[AVCaptureMovieFileOutput alloc] init];
self.movieFile.minFreeDiskSpaceLimit = 1024 * 1024;

CMTime maxDuration = CMTimeMakeWithSeconds(60*60, 240); // 1 hour at 240 fps should be more than enough
self.movieFile.maxRecordedDuration = maxDuration;
if ([self.camera.capSession canAddOutput:self.movieFile])
    [self.camera.capSession addOutput:self.movieFile];

我要去哪里错了?

这是ffprobe在结果文件上的输出.

This is the output from ffprobe on the resulting file.

Stream #0:0(und): Video: h264 (High) (avc1 / 0x31637661), yuv420p(tv, bt709), 1920x1080, 15166 kb/s, 30 fps, 30 tbr, 600 tbn, 1200 tbc (default)

但是，这就是activeFormat的本意:

But yet, this is what the activeFormat supposedly is:

AVCaptureDevice: <AVCaptureDeviceFormat: 0x17401f780 'vide'/'420f' 1280x 720, { 6-240 fps}, fov:59.680, binned, supports vis, max zoom:65.50 (upscales @1.45), AF System:1, ISO:22.0-704.0, SS:0.000002-0.166667, supports wide color>

推荐答案

我最终回答了自己的问题.

I ended up answering my own question.

除了使用预设外，我发现为了设置摄像机配置，我需要将摄像机添加到捕获会话中，对其进行配置，然后立即启动捕获会话.而我是在配置摄像机之前将摄像机添加到捕获会话的，这似乎并没有导致配置被提交.

In addition to using a preset, I discovered that in order to set the camera configuration, I need to add the camera to the capture session, configure it and then start the capture session immediately. Whereas, I was adding the camera to the capture session before I had configured it, which doesn't seem to cause the configuration to be committed.

相关的iOS文档: https://developer.apple .com/reference/avfoundation/avcapturedevice/1387810-lockforconfiguration?language = objc

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