AVAssetTrack preferredTransform 总是返回横向

Question

我有一个可以录制视频的应用。

要处理手机轮换，我有以下代码：

    // called on phone rotation
    AVCaptureConnection *previewLayerConnection = [[self previewLayer] connection];
    if ([previewLayerConnection isVideoOrientationSupported]) {
        [previewLayerConnection setVideoOrientation:[self getVideoOrientation]];
    }

和getVideoOrientation函数：

- (AVCaptureVideoOrientation) getVideoOrientation {
    UIInterfaceOrientation deviceOrientation = [[UIDevice currentDevice] orientation];
    AVCaptureVideoOrientation newOrientation = AVCaptureVideoOrientationPortrait;
    switch (deviceOrientation) {
        case UIInterfaceOrientationPortrait:
            NSLog(@"UIInterfaceOrientationPortrait");
            newOrientation = AVCaptureVideoOrientationPortrait;
            break;
        case UIInterfaceOrientationLandscapeLeft:
            NSLog(@"UIInterfaceOrientationLandscapeRight");
            newOrientation = AVCaptureVideoOrientationLandscapeLeft;
            break;
        case UIInterfaceOrientationLandscapeRight:
            NSLog(@"UIInterfaceOrientationLandscapeLeft");
            newOrientation = AVCaptureVideoOrientationLandscapeRight;
            break;
        default:
            NSLog(@"default");
            newOrientation = AVCaptureVideoOrientationPortrait;
            break;
    }

    return newOrientation;
}

应用程序的这部分工作正常（我可以在任何设备方向上看到视频）。 但是当我尝试制作缩略图（或播放视频）时，我遇到了问题。

正如我在其他问题中所读到的，我对每首曲目执行以下操作：

        AVAssetTrack* videoTrack    = [[asset tracksWithMediaType:AVMediaTypeVideo] objectAtIndex:0];
        CGAffineTransform txf       = [videoTrack preferredTransform];
        CGFloat videoAngleInDegree  = RadiansToDegrees(atan2(txf.b, txf.a));

        if (txf.a == 0 && txf.b == 1.0 && txf.c == -1.0 && txf.d == 0) {
            thumbOrientation = UIImageOrientationLeft;
        }
        if (txf.a == 0 && txf.b == -1.0 && txf.c == 1.0 && txf.d == 0) {
            thumbOrientation =  UIImageOrientationRight;
        }
        if (txf.a == 1.0 && txf.b == 0 && txf.c == 0 && txf.d == 1.0) {
            thumbOrientation =  UIImageOrientationUp;
        }
        if (txf.a == -1.0 && txf.b == 0 && txf.c == 0 && txf.d == -1.0) {
            thumbOrientation = UIImageOrientationDown;
        }

        UIImage *image = [UIImage imageWithCGImage:im scale:1.0 orientation:thumbOrientation];

我有 2 个示例文件：1 - 横向右侧，2 - 横向左侧。我希望它们在上面的代码中具有不同的方向，但出乎意料的是它们具有相同的方向（并且它们的 videoAngleInDegree 是相同的）。

有什么解决办法吗？

Answer 1

您确定它工作正常吗？那里的getVideoOrientation 看起来不对——AVCapture 和 UIDevice 对于左右横向的含义相反。

这是来自this question 的正确实现——查看那里的讨论，看看是否有帮助。

- (void)deviceOrientationDidChange{

    UIDeviceOrientation deviceOrientation = [[UIDevice currentDevice] orientation];

    AVCaptureVideoOrientation newOrientation;

    if (deviceOrientation == UIDeviceOrientationPortrait){
        NSLog(@"deviceOrientationDidChange - Portrait");
        newOrientation = AVCaptureVideoOrientationPortrait;
    }
    else if (deviceOrientation == UIDeviceOrientationPortraitUpsideDown){
        NSLog(@"deviceOrientationDidChange - UpsideDown");
        newOrientation = AVCaptureVideoOrientationPortraitUpsideDown;
    }

    // AVCapture and UIDevice have opposite meanings for landscape left and right (AVCapture orientation is the same as UIInterfaceOrientation)
    else if (deviceOrientation == UIDeviceOrientationLandscapeLeft){
        NSLog(@"deviceOrientationDidChange - LandscapeLeft");
        newOrientation = AVCaptureVideoOrientationLandscapeRight;
    }
    else if (deviceOrientation == UIDeviceOrientationLandscapeRight){
        NSLog(@"deviceOrientationDidChange - LandscapeRight");
        newOrientation = AVCaptureVideoOrientationLandscapeLeft;
    }

    else if (deviceOrientation == UIDeviceOrientationUnknown){
        NSLog(@"deviceOrientationDidChange - Unknown ");
        newOrientation = AVCaptureVideoOrientationPortrait;
    }

    else{
        NSLog(@"deviceOrientationDidChange - Face Up or Down");
        newOrientation = AVCaptureVideoOrientationPortrait;
    }

    [self setOrientation:newOrientation];
}