hdr dolby vision video color correction to 8 bit still images

fyi we had an apple office hours meeting to address this, this is the first part of the solution we found based on those discussions

pixel format needed to change, and 3 dictionary key values added to AVAssetReaderTrackOutput outputSettings: argument per below

with these, the UIImage seem to come out much better but we havent done a full check yet

the next step is to get these images written back to a video file w/o losing their color again

this is just a code snippet, if anyone needs to full code we can post the full xcode sample as we have extracted the buggy dolby stuff into a small test case

the info about the color properties (noted below) we had found previously in the apple docs about this technology, but it also needed the updated pixel key to cause any positive effect on the outputted images. that part was not clear from the docs immediately.

NSArray* video_tracks = [asset tracksWithMediaType:AVMediaTypeVideo]; 
AVAssetTrack* video_track = [video_tracks firstObject];
NSMutableDictionary* dictionary = [[NSMutableDictionary alloc] init];
// kCVPixelFormatType_32BGRA // this was the what we had
// 420YpCbCr8BiPlanarFullRange // this is the correct one (see next line)

[dictionary setObject:[NSNumber numberWithInt:kCVPixelFormatType_420YpCbCr8BiPlanarFullRange] forKey:(NSString*)kCVPixelBufferPixelFormatTypeKey];

// this is also needed

dictionary[AVVideoColorPropertiesKey] =

            @{AVVideoColorPrimariesKey:

                AVVideoColorPrimaries_ITU_R_709_2,

            AVVideoTransferFunctionKey:

                AVVideoTransferFunction_ITU_R_709_2,

            AVVideoYCbCrMatrixKey:

                AVVideoYCbCrMatrix_ITU_R_709_2};

        AVAssetReaderTrackOutput* asset_reader_output = [[AVAssetReaderTrackOutput alloc] initWithTrack:video_track outputSettings:dictionary];

Can you please post sample code which you mentioned that would be great help. thanks in advance