AVAssetWriter settings for ProRes422

AVAssetWriter will write a new file, not edit an existing file. Perhaps you meant AVAssetReader or AVMutableComposition?

Well I meant editing a video rather than recording a video (in which case you get recommendedSettings from AVCaptureVideoDataOutput for writing using AVAssetWriter). If you want to edit a video using AVMutableComposition and exporting it using AVAssetReader and AVAssetWriter combination, then I am not sure what should be filled in compression dictionary (AVVideoCompressionPropertiesKey) for ProRes video.

Ah, I see. You might try AVOutputSettingsAssistant, but it looks like that class does not have a dedicated preset for ProRes. I'm guessing that you are using AVAssetReader/Writer because you want to modify the samples before writing them to disk, but if that's not the case you could use AVAssetExportSession and one of its ProRes presets.

There is no API for getting recommended ProRes settings based on an input file, unless you count AVAssetExportSession which implicitly chooses settings on your behalf. It does seem like a mismatch that there are ProRes export session presets but no ProRes preset for AVOutputSettingsAssistant. Would you mind filing a feedback assistant report for us to improve that?

FB9709363 filed!