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Does converting an mp3 format audio file to m4a format makes audio quality better ? I was just wondering if mp3 is lossy. How it can generate lossless m4a file after conversion. I know mp3 can be converted to m4a but will this m4a file will give the same audio quality as compared to an originally created m4a file.

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No. Once lossy formats are encoded, any data not saved within the file is lost. You could convert a lossy MP3 to a WAV or an M4A file but the quality of the WAV or M4A would be exactly the same as the original MP3.

  • pfarley, are you sure there will not be any loss when transcoding from mp3 to m4a? this would only be the case if transcoding to a lossless format (despite the container (m4a/flac). – Arnoud Traa Jul 20 '14 at 10:53
  • I wanted to stress that you won't get lost data back and was probably a bit misleading, sorry. If you converted to another lossy codec (even if it's 'higher-quality' than what you're converting from) you can still lose data. – pfarley Jul 21 '14 at 11:10
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It might be that you loose even more quality due to another file compression algorithm.

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It is mathematically impossible to improve any digital audio stream to a "Better Quality" by a simple conversion to said file type. A poor quality mp3 can be "converted" to any format you like but the poor quality will remain and, as mentioned, you may even lose a bit in the conversion.

There seems to be some misconceptions floating around out there about stepping up quality as many programs allow you to import lossy or low quality audio into a workspace that may be set at a high quality/resolution. That being said the lossy or low quality audio does not get any "better" in doing so. The fundamental problem is that you cant insert samples into a track. you can estimate them (although aliasing can be an issue) but you can't fundamentally insert them.

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Just to add & clarify that m4a is a container format, actually the same spec as mp4, merely a different file extension, and therefore can contain either AAC (lossy) or ALAC (lossless) formats -- or even mp3! -- so the question as stated doesn't make sense (same with many of the answers & comments).

Regardless, the simple answer to the intended question is that converting a lossy format to a non-lossy format inherently can't make audio quality "better" (literally: no new information can be added to the data via this transformation). In theory, the very best you can do is achieve the same quality; in practice, you'll probably lose a little quality, but carefully selecting the right conversion & format options you might not notice the degradation.

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As far as I know, m4a is also considered to be a lossy format. So converting from lossy to lossy would not make any difference, probably worsen the quality depending on the coding standard being used.

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I think it's important to understand: Rakesh, what is your motivation for converting? Also, within M4A, are you specifically referring to http://en.wikipedia.org/wiki/Apple_Lossless ?

Clarifying this will help with useful answers.

  • No, i am referring to m4a in general. And, i could not understand what you meant by 'motivation for converting' because in my view it does not matter because it won't change the result anyway. – Rakesh Chandra Jul 19 '14 at 18:03
  • I was just asking that 'how can one mp3 file (lossy) can generate an m4a file which is lossless. But, i think @pfarley has clearified that even when we convert an mp3 fule to an m4a format, it will change the format but the quality will be the same as the source mp3 file. – Rakesh Chandra Jul 19 '14 at 18:08

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