Does Converting FLAC To FLAC Lose Quality?

Loss of sound quality is common when converting audio files from one format to another. But what if you encode to the same format? Is there a loss of quality if, for instance, one converts FLAC to FLAC?

A FLAC (Free Lossless Audio Codec) file does not lose sound quality when converting to FLAC unless the bit rate is reduced during the conversion. FLAC uses lossless compression, so no audio data is lost during the conversion process, allowing the new file to replicate the quality of the original.

Before converting an audio file, it is always advisable to have a clear expectation of how the conversion process will affect the sound quality of the new file. Anyone thinking about converting FLAC to FLAC who is concerned about losing sound quality might want to consider the knowledge and insight presented below.

Does FLAC To FLAC Conversion Reduce Sound Quality?

Converting audio files can result in the loss of sound quality. This issue occurs when encoding to different formats or between the same codec. Fortunately, a file’s quality does not diminish when converting from FLAC to FLAC (though this is technically not conversion as the identical format).

Converting FLAC to FLAC retains the original file’s quality because the codec uses lossless compression. The central purpose of lossless compression is to compress audio files without losing data.

This form of audio compression creates new, smaller files encoded with all of the aurally perceptible and significant data from the source audio.

Lossless compression also discards information that is not audible or does not contribute to the overall sound quality. The data is held in an index file. This means one can reverse the compression process
at a later stage, and restore the audio data to its initial form.

So, if one converts from FLAC to FLAC, the audio quality will remain the same. The new file will accurately replicate the sound quality of the original. The only scenario when this conversion diminishes the quality is when one encodes the new file at a lower bit rate.

It is worth examining the FLAC codec and its compression process to understand its implications for audio quality.

A Closer Look At FLAC Lossless Compression

FLAC is a free audio encoder format developed by the Xiph.Org Foundation. The encoder processes high-quality linear pulse-code modulation data (LPCM), which is standard on compact discs.

The FLAC Algorithm

The FLAC algorithm encodes audio data through lossless compression:

  • input data gets separated into discrete blocks,
  • linear predictive coding (or a polynomial) provides an accurate mathematical approximation of each block,
  • the algorithm produces a description of the approximation,
  • Rice coding encodes the residual (the deviation between source data and the approximation).

At the end of the encoding procedure, a new lossless compression file is created that accurately replicates the waveform of the source data with 50% to 70% fewer bits. Unlike lossy codecs, FLAC encoders do not lose essential audio information but retain it in approximate form. 

When decoding an audio file, the FLAC algorithm operates as follows:

  • the residual is decoded,
  • the description of the approximation serves as the basis for a waveform calculation,
  • the calculation and residual are combined to produce the decoded output waveform.

This decoding process enables FLAC files to produce the exact same waveform as the source audio data.

Lossless compression makes it possible to convert from FLAC (and other codecs) to FLAC without any perceivable loss in sound quality. The principal variable that would diminish the quality of the new file is the bit rate. Encoding at a lower bit rate than the original FLAC file reduces the signal-to-noise ratio of the new file.

What Are The Reasons To Convert From FLAC To FLAC?

While one can convert from FLAC to FLAC without diminishing the audio quality of the new file, are there any reasons to do this? The process of converting a FLAC file into the same format requires time and effort to undertake. Is it worthwhile if the process does not improve the sound quality of the newer version?

Indeed, it is generally not necessary to convert from FLAC to FLAC. There are specific scenarios, however, when converting FLAC to FLAC is desirable.

Lowering The Bit Rate

Encoding FLAC to FLAC is beneficial if one wishes to lower the bit rate of the new file. Lowering the bit rate is desirable when seeking to maximize the efficiency of hard-drive storage, and preserving audio quality is not a priority.

When converting at a lower bit rate, the newly-created FLAC file becomes smaller, and the signal-to-noise ratio deteriorates. Reducing the bit rate marginally does not affect the sound significantly. However, converting from a high bit rate like 1411kbps to a low 128kbps will result in a noticeable deterioration of sound quality.

Convert To The Latest Version Of FLAC

Encoding audio data in the latest version of FLAC is another reason for converting files that are already in this format.

The Xiph.Org Foundation has released several iterations of the FLAC format, with Version 1.4.2 being the latest (released in 2022). Meticulous audiophiles might choose to convert FLAC files to a newer version of the codec, so they can benefit from improvements made to the encoder.

Version 1.4.2 features several improvements to the codecโ€™s build system. The latest version of FLAC also provides increased uniformity of the console output on multiple CPUs and platforms.

Decreasing The Size Of The File

One may also wish to encode a FLAC file to FLAC to decrease the size of the original file.

It is somewhat surprising to note that, when converting FLAC to FLAC, there is a reduction in the file size (as much as 1MB). The new, smaller files produce audio quality comparable to the original.

What Is The Highest Quality FLAC File?

The quality of FLAC files depends on the original audio and the bit rate.

FLAC files faithfully reproduce the quality of the source audio data. Muddied and artifact-laden input data will result in lower-quality FLAC files.

The bit rate is another variable that affects the quality of FLAC files. FLAC files sound better when encoded at higher bit rates because they contain and convey more audio information. The highest bit rate that the FLAC codec supports is 1411kbps. The most superior quality FLAC files would invariably be at this bit rate.

What Is A Better Format Than FLAC?

FLAC files generally sound better than lossy codecs like MP3, though the difference is barely audible to most listeners. However, uncompressed formats like WAV (Waveform Audio File Format) and AIFF (Audio Interchange File Format) produce a better quality sound than FLAC.

Unlike the FLAC codec, WAV and AIFF formats encode all the source audio in raw form without compressing the data for space efficiency.

It is worth emphasizing, though, that the difference in quality between uncompressed formats like WAV and AIFF, and FLAC is not substantial. Unless listeners have well-trained ears, they are unlikely to discern the between these formats (provided the files are encoded with the same settings).

Uncompressed formats also have the disadvantage of producing large file sizes compared with FLAC.

Conclusion

If one converts an audio file from FLAC to FLAC, there is no loss of audio quality. The FLAC algorithm encodes audio data using lossless compression, so the new FLAC file will sound indistinguishable from the source audio.

Encoding a FLAC file to the same format at a lower bit rate will diminish the sound quality of the second file.

In most instances, there is no tangible benefit to converting FLAC to FLAC. The process might be beneficial if one wishes to reduce the bit rate of the files or to transfer the audio data to the latest version of the FLAC codec.

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