canSetSessionPreset:AVCaptureSessionPreset1920x1080在iPhone 4上返回'yes'

Question

我想检查iPhone用户是否支持全高清视频捕获.我发现,我应该问AV会议,如果

avSession = [[AVCaptureSession alloc] init];
    [avSession beginConfiguration];
    if ([avSession canSetSessionPreset:AVCaptureSessionPreset1920x1080]) {
        avSession.sessionPreset = AVCaptureSessionPreset1920x1080;
        NSLog(@"FULLHD");
    } else {
        avSession.sessionPreset = AVCaptureSessionPreset1280x720;
        NSLog(@"HDREADY");
    }
    [avSession commitConfiguration];

这在iPhone 5上运行良好(它确实支持全高清捕获),但在iPhone 4上也尝试设置预设,但显然失败了.我究竟做错了什么？

先谢谢,马蒂亚斯

Answer 1

在向捕获会话添加输入后,您是否调用了canSetSettingPreset？

[captureSession addInput:captureInput]; // <--- you should add an input before canSetSessionPreset
[captureSession addOutput:captureOutput];


if( [captureSession canSetSessionPreset:AVCaptureSessionPreset1280x720] == YES ) {
    captureSession.sessionPreset = AVCaptureSessionPresetiFrame1280x720;
} else {
    captureSession.sessionPreset = AVCaptureSessionPreset640x480;
}