OptimFrog can be considered a unique format even among lossless audio codecs. It seems that the developer focused more on scientific research than on the actual use of his idea in the real world. As a result, we got a strange mixture of advanced algorithms, very low performance and many missing features. It's like a giant with feet of clay.
1 Key features of OptimFROG
In terms of compression, it is an absolute champion, but the result comes at a high price - the compression speed is extremely low. Just imagine, when testing codecs for OptimFrog, the maximum compression mode is never used.
This is the second lossless codec I know of after WavPack that supports compression of samples in 32-bit floating point format. In the article about WavPack, I already wrote how important such support is when editing sound, so I will not list the arguments again. I will simply say that the ability to halve the size of files at the cost of a few seconds is very useful.
DualStream mode is also very similar to WavPack Hybrid compression, it creates a main lossy file and a correction file. But as I already said, OptimFrog requires an order of magnitude more resources and no player I know is capable of playing DualStream in real time. It is hard to imagine, given the computing power of modern processors.
2 Why conversion is necessary
It also has plenty of disadvantages. In technical terms, the main drawback is the lack of multichannel sound support. I'm sure the author could have added it himself or passed the source code to the opensource community. But that didn't happen. The author stopped further development and no updates were released after 2017.
Support for mobile devices was not provided from the beginning, although due to the high resource intensity of the algorithm, it would hardly have been widely distributed. Of course, hardware support is out of the question. Even software support is limited to official utilities and foobar2000 plugin.
Thus, we have a codec designed for maximum compression, but very greedy and poorly supported. I don't think that extra 5% of disk space saving is worth it. If you need its unique features like hybrid compression support and 32-bit samples, the only alternative is WavPack. For all other cases FLAC will be the preferred option. This article will tell you how to perform such conversion.
3 OFR to FLAC conversion guide
I warn you right away - it will not be easy to find a suitable converter. Even the most famous all-in-one tool FFMPEG does not support this format. The native converter from the developer is not very functional and does not support tag transfer. After a Google search I found a few converters, but they all look abandoned and haven't been updated in years. Damn, it's been a long time since I've encountered one of these. It seems that Audio Converter Plus is the last converter that provides full support for this format.
Advantages of Audio Converter Plus
- Fast lossless format conversion
- Wide range of supported audio formats.
- Correct copying of audio tags between different formats
- Effective use of multi-core processors
- Download and install Audio Converter Plus from the link above.
- Launch Audio Converter Plus and add OFR files to the conversion list. It's easier to add albums in their entirety via the "Add Folder" menu item.
- Select the output folder and output format as FLAC, and make sure the sample rate setting is set to "As Original".
- Open Settings and turn on the "Transfer Audio Tags" option. It will read the metadata from the OFR file, convert it and save it to a FLAC file.
- Enable the "Keep directory structure" option. This will allow you to distribute the output FLAC files into folders, as was the case with the original FLAC files.
- Start the conversion by clicking the "Convert" button. After this, a progress window will appear, but there is little point in watching it. It's easier to send the conversion process into the background and go about your usual business.
4 Summary
So, we had a chance to get acquainted with a codec that many people have never even heard of. Perhaps it still has its fans on HydrogenAudio, but even the most devoted ones have not yet reversed the codec to add its implementation to FFMPEG. In my opinion, it means that nobody is interested in the codec. If you somehow got audio files compressed by OptimFROG, you should convert them to a more suitable format. This is the rare case when I recommend conversion with 100% certainty. Thankfully, lossless compression allows you to do it without much trouble.