OptimFROG DualStream is a lossy codec designed to bridge the gap between perceptual coding and lossless coding. The codec has the option to produce a correction file, which can be used in combination with the main lossy-encoded file for lossless decoding. WavPack and MPEG-4 SLS also offer the same correction feature.
The codec has been designed to offer real transparent audio coding at reduced bitrate and to permit progressive consistent increase of the quality level till lossless coding is achieved. The release version has passed extensive testing and uses mathematically proven algorithms.
The codec is a branch of the main OptimFROG version 4.509 project that comes with modifications for extended functionality and different file extension, to avoid mixing up of lossless and lossy files. The codec allows for independent listening levels and is suitable for further editing and transcoding. It is also suitable for computer processing of audio data and provides independent quantization levels for each channel.
The other advantages of the codec include correction file option for lossless restoration of the original file and excellent handling of artificial and low complexity audio data. Apart from these, the error signal is small in amplitude, and there are no frequency domain artifacts. However, it doesn’t consider the human auditory system limitations and requires a higher bitrate to achieve perceptual transparency.