What exactly is generation loss?

When you open a lossy file, edit it, and save it again as lossy, the compression algorithm analyzes the audio a second time and discards information again. Every time that cycle repeats, the sound degrades a little further; this is generation loss. It's like photocopying a photocopy. Using WAV during editing breaks the cycle, because saving a WAV discards nothing.

Can't DAWs open M4A files directly?

Most modern DAWs can import an M4A file, but they typically do so by decoding it to an uncompressed form in the background. Some software doesn't support M4A at all, or behaves unpredictably with it. Compressed files are also slower to scrub back and forth on a timeline, because each access requires decoding. WAV removes that intermediate layer.

If I convert M4A to WAV, edit it, and convert back to M4A, is there loss?

Lossy compression is applied once on that final save, and that's unavoidable. What matters is that the entire editing process happened on WAV, so no additional loss accumulated across the dozens of operations in between. In total you go through two generations of lossy compression: the original M4A and the final export. That's a far cleaner result than re-compressing on every save.

Do I need to convert to WAV for every editing job?

No. If you're only trimming a track or joining two files, many tools can do that directly without re-encoding, and converting to WAV brings no benefit. Moving to WAV makes sense when you're going to genuinely process the audio: level adjustment, EQ, noise reduction, multi-channel mixing, and the like.

Why Converting M4A to WAV Matters for Editing

An operation that looks pointless

You have a 4 MB M4A file. You convert it to WAV and the file becomes 40 MB. The audio is exactly the same — not better. You've produced a file that occupies ten times the space and delivers no quality gain at all.

At first glance this is a pointless operation. Yet everyone who works with audio editing does it routinely, and there's a good reason. That reason has nothing to do with the file's current quality and everything to do with what happens to it during the process.

The core issue: generation loss

Lossy compression has a property that doesn't get discussed much: it does fresh damage every time it's applied.

When an encoder like AAC compresses audio, it discards the information least likely to be noticed by the human ear. Done once, the result is usually perfectly good. But if you open a compressed file, work on it, and compress it again, the encoder is this time analyzing audio that has already been processed once. The material in its hands isn't the original; it carries the traces of the first compression. The new compression adds its own losses on top of those traces.

Repeat that a few times: with each pass the sound thins slightly, high frequencies grow muddier, and a faint shimmer appears around drum hits. It's like a photocopy of a photocopy — a single copy is fine, the fifth is unreadable.

Think about a podcast episode: you trim the recording, save. The next day you adjust levels, save. Then you clean up noise, save. You add music, save. If you're working in a lossy format, you've accumulated four generations of loss.

WAV breaks that cycle. Because WAV applies no compression, saving discards no information. Open and save it a hundred times and the audio stays identical at the bit level. Staying in WAV throughout editing and compressing only at the very end reduces total loss to a single generation.

The second reason: making life easier for the software

When you scrub back and forth on a timeline in a DAW or video editor, the software needs to locate the audio at that instant immediately.

In WAV this is simple: audio is stored as raw data in linear form. When you say "twelve seconds in," the software jumps straight to the corresponding point in the file.

With a compressed file the situation differs. AAC data is encoded in blocks, and reaching a specific moment requires decoding that region. On modern computers this is usually fast, but the difference becomes noticeable if you're working with dozens of audio channels at once, looping a short section repeatedly, or already pushing your computer hard: stutters, delayed response, playback errors.

This is why professional workflows automatically decode compressed files to an uncompressed form on import. The software is already doing what you would otherwise do by hand.

The third reason: compatibility and delivery

In some situations WAV isn't a preference but a requirement:

CD production: The standard is precisely 44.1 kHz, 16-bit PCM.
Broadcast and production deliverables: Many organizations require delivered audio to be uncompressed.
Legacy or specialized software: Some analysis tools, game engines, and embedded systems read only WAV.
Sound design libraries: Sample libraries generally expect WAV.

In these scenarios the file's size isn't a cost — it's a necessity.

So is making a WAV from a lossy source dishonest?

A fair question. When you convert a lossy M4A to WAV, what comes out is audio labeled "WAV" that is in fact lossy. Someone seeing the file might assume it's studio quality.

Let's be precise here: the conversion does not improve the audio. An AAC file converted to WAV sounds identical to the original AAC — it merely occupies more space. If what you have is a 128 kbps recording, converting to WAV does not turn it into a studio recording.

Therefore:

Converting to WAV for editing: Sensible. You prevent additional loss from accumulating during processing.
Converting in the expectation of higher quality: Meaningless. No gain, only lost disk space.
Converting to present the file as high quality: Misleading. The source is what it is.

If your M4A contains ALAC (Apple Lossless), the picture changes: that is already lossless, and converting to WAV leaves the audio bit-for-bit identical. In that case moving to WAV is simply a change of container.

A practical workflow

If you're going to edit audio, this is the order to follow:

Convert the source to WAV. With our conversion tool, preserving the sample rate and choosing 24-bit for editing.
Do all editing on the WAV. Trimming, levels, effects, mixing — all at this stage.
Keep intermediate saves as WAV too. It takes space, but loss doesn't accumulate.
Compress only at the very end, for distribution. MP3, AAC, or whatever your target requires.
Keep the WAV working files until the project is finished. If a revision comes in later, you won't be starting over.

In summary

Converting M4A to WAV enlarges the file without improving the sound — and that was never the point. The point is to prevent the loss that repeated compression accumulates during editing, to let software handle the file smoothly, and to produce output suitable for systems that require WAV. If you're only going to listen, leave your M4A alone; if you're going to work on it, moving to WAV is the right way to begin.