AVVideoComposition 应用过滤器处理程序不调用

I want to add an overlay image into a video. I use AVVideoComposition and CIFilter to do this, but AVAsynchronousCIImageFilteringRequest handler not called. I put some breakpoints (line debugPrint"Here", request.finish), but XCode doesn't hit the breakpoints.

我收到了视频，但是没有水印。

func watermark(video asset: AVAsset, with image: UIImage, output outURL: URL) {
        guard let watermarkImage = CIImage(image: image) else {
            return
        }

        let context = CIContext(options: nil)

        let videoComposition = AVVideoComposition(asset: asset) { (request) in
            debugPrint("Here")
            let source = request.sourceImage.clampedToExtent()

            let watermarkFilter = CIFilter(name: "CISourceOverCompositing")

            watermarkFilter?.setValue(source, forKey: kCIInputBackgroundImageKey)

            let transform = CGAffineTransform(translationX: request.sourceImage.extent.width - watermarkImage.extent.width - 10, y: 10)
            watermarkFilter?.setValue(watermarkImage.transformed(by: transform), forKey: kCIInputImageKey)
            guard let outputImage = watermarkFilter?.outputImage else {
                return
            }

            request.finish(with: outputImage, context: context)
        }

        let exporter = AVAssetExportSession(asset: asset, presetName: AVAssetExportPresetPassthrough)
        exporter?.outputFileType = .mov
        exporter?.outputURL = outURL
        exporter?.videoComposition = videoComposition
        exporter?.exportAsynchronously { [weak exporter] in
            guard let export = exporter else {
                return
            }

            switch export.status {
            case  .failed:
                print("failed \(exporter?.error)")
                break
            case .cancelled:
                print("cancelled \(exporter?.error)")
                break
            case .completed:
                print("complete")
            default:
                print("default")
            }
        }
    }

您不应将直通预设与 CI 过滤一起使用。尝试使用另一个定义视频格式的预设。

这个文档 https://developer.apple.com/library/archive/qa/qa1744/_index.html没有具体提到 CI 过滤，但它指出使用直通预设会导致层指令被忽略。我希望 CI 过滤也是一样的。

重要提示：如果您使用 AVAssetExportSession 对象导出视频合成并指定 AVAssetExportPresetPassthrough 导出预设以让所有轨道通过，则将不会应用视频合成指令 (AVMutableVideoCompositionLayerInstruction) 中定义的变换。您必须将导出预设更改为定义视频格式的导出预设（例如 AVAssetExportPresetMediumQuality）才能应用转换。