Windows encodes M4A and MP3 at the same bitrate, so the file sizes land 0.6% apart
"Convert M4A to MP3 to save space" is advice you see everywhere. I measured it with the encoders that ship in Windows, and on the same source the two files came out 0.6% apart . Here is what is actually going on, and the PowerShell that does the conversion without installing anything. The setup One 10-second, 44.1kHz, 16-bit stereo WAV — 1,764,044 bytes, which Windows reports as 1,411,200 bps…
Windows encodes M4A and MP3 at the same bitrate, resulting in file sizes that are only 0.6% apart. To demonstrate this, a 10-second, 44.1kHz, 16-bit stereo WAV file (1,764,044 bytes) was converted to M4A and MP3 using Windows' built-in encoders. The M4A files were created at three different quality settings, while the MP3 files were encoded at the "High" preset.
Despite using different codecs, the MP3 and M4A files with the same preset had identical bitrates of 192kbps. The difference in file sizes comes from container overhead, not the actual audio quality. Converting M4A to MP3 does not save space, as the recovered WAV file after the conversion is larger than the original WAV. Additionally, converting back and forth between formats results in a larger file size, indicating that the discarded audio during encoding is not recoverable.
Windows reports slight variations in the duration of each file, due to encoder delay and padding. If multiple converted clips are stitched together, these variations can cause audible clicks at the junctions. Although Windows comes with these encoding tools, PowerShell can access them through the WinRT interface.
Written by urgent.news from Dev.to's reporting — not their text. Machine-written — may contain errors; check the original before relying on it.
