am using AVAssetReaderAudioMixOutput with audioSettings for playing the audio file. I am facing issue with iOS 14

The audio setting i have used is

NSDictionary* sampleRateDict = @{ AVSampleRateKey: @(44100), AVFormatIDKey: @(kAudioFormatLinearPCM) };

This works completely fine with iOS 13 and below but not in iOS 14.
I managed to identify the issue and when i change my settings as

NSDictionary* sampleRateDict = @{ AVSampleRateKey: @(44100), AVFormatIDKey: @(kAudioFormatLinearPCM), AVLinearPCMBitDepthKey: [NSNumber numberWithInt:16], AVLinearPCMIsFloatKey: [NSNumber numberWithBool:NO] };

AVAssetReaderAudioMixOutput* audioOutput = [[AVAssetReaderAudioMixOutput alloc] initWithAudioTracks:audioTracks audioSettings:sampleRateDict];

This works charm in iOS 14 and below. Is there any official change document for this from apple ?