         let formatDesc = audioContext.assetTrack.formatDescriptions
         for item in formatDesc {
             // TODO: handle error here
-            guard let fmtDesc = CMAudioFormatDescriptionGetStreamBasicDescription(item as! CMAudioFormatDescription) else { return }    // TODO: Can the forced downcast in here be safer?
+            guard let fmtDesc = CMAudioFormatDescriptionGetStreamBasicDescription(item as! CMAudioFormatDescription) else { return nil }    // TODO: Can the forced downcast in here be safer?
             channelCount = Int(fmtDesc.pointee.mChannelsPerFrame)
         }
 

        // if (reader.status == AVAssetReaderStatusFailed || reader.status == AVAssetReaderStatusUnknown)
        // Something went wrong. Handle it.
        if reader.status == .completed {
            done(outputSamples, sampleMax)
        } else {
            print(reader.status)
        }
    }
    

//            return
//        }
//        UIGraphicsEndImageContext()
    }
}

