Question 1

Does merging re-encode the audio?

Accepted Answer

Yes. Each file is decoded and the result is encoded again as a single AAC stream. AAC is a lossy format, so the merged file is not a bit-for-bit copy of your originals. The change is usually small, but merging an already re-encoded file repeatedly will compound it.

Question 2

What bitrate will the merged file use?

Accepted Answer

The merged file is encoded at a target bitrate of 192 kbps. This is fixed and does not depend on the bitrates of your source files. A higher output bitrate cannot restore detail that was already lost in a lower-bitrate source file.

Question 3

Can I merge AAC files with different bitrates, sample rates, or channel counts?

Accepted Answer

Yes. The first file determines the sample rate and number of channels of the merged output. Files with different settings are adjusted to match it. For the most consistent result, use files recorded with the same settings.

Question 4

Does the order of the files matter?

Accepted Answer

Yes. The files are merged in the order shown. You can rearrange them before merging. The first file also determines the output's sample rate and number of channels.

Question 5

Can I add M4A or MP4 files here?

Accepted Answer

No. This tool accepts files with a.aac extension or an AAC file type. M4A files hold AAC audio too, but they use a different container, so they are ignored here. Use the Merge M4A files tool for those.

Question 6

Will the merged file keep titles, artists, or cover art?

Accepted Answer

No. The output is a raw AAC stream, which carries the audio and nothing else. If you want a file that holds metadata, convert the merged file to M4A afterwards. That conversion rewraps the same AAC audio without re-encoding it, so the quality does not change again.

Question 7

Does the tool add gaps, crossfades, or normalize the volume?

Accepted Answer

No. The files are placed directly one after another. The tool does not intentionally add silence, create crossfades, or normalize loudness. Differences in volume and anything already present at the file boundaries will remain.

Question 8

What can I use the AAC merger for?

Accepted Answer

You can join a recording that your device split into numbered segments, combine podcast or interview parts into one episode, or turn a set of captured stream clips into a single file for easier playback.

Merge AAC files

Frequently Asked Questions