Combine MP3 and encode to AAC?

[rack04]

I have a series of MP3 files that make up an audiobook. Can anyone provide guidance on how to combine the MP3 files into a single file and encode to AAC? I want to import the new file into iTunes so that I don't have to keep selecting the new tracks. Thanks.

[LoRd_MuldeR]

If those are "plain" MP3 files and they have the same sample-rate, they can be combined simply via COPY command:
COPY /B file1.mp3 + file2.mp3 + file3.mp3 combined.mp3

You can of course achieve the same thing with the audio editor of your choice, such as Audacity (http://audacity.sourceforge.net/) - just be sure you save the result to uncompressed Wave.

Alternatively, if you wish to retain the original MP3 bitstream, you can use mp3DirectCut (http://mpesch3.de1.cc/mp3dc.html).

In order to convert the combined file to AAC, you may use, for example, FAAC, Nero AAC or QAAC - maybe with some encoder GUI (https://forum.doom9.org/showthread.php?t=157726) of your choice ;)

[detmek]

Also, foobar2000 can combine files during coversion if you select single file output. And thanks to ability to use DSP filters during conversion process files do not have to have same characteristics li bitrate, samplerate, bitdepth or number of channels.
You just need proper CLI encoder like Nero AAC encoder.

[rack04]

Thanks for the options presented so far. What about adding "chapter" marks at the merge point?

[LoRd_MuldeR]

Thanks for the options presented so far. What about adding "chapter" marks at the merge point?

MP4Box should be able to add chapter information to an MP4. See "-chap" option:
http://gpac.wp.mines-telecom.fr/mp4box/mp4box-documentation/ (http://gpac.wp.mines-telecom.fr/mp4box/mp4box-documentation/#meta)

[detmek]

Also posible with foobar (multi-track file output). But only if you convert to mp4/m4a. If output format is mp3 fb2k generates external cue file.
P.S. I appolgize, but I'm just a little bit of foobar fan and I use it for every conversion process. I also use it as player, audio cd ripper and tagger.

[CarlEdman]

Yes, putting in chapter markers is definitely a good idea.

Unfortunately, I don't know of any tool that does this automatically while merging chapter files. Your best bet, or at least what I do, is to extract the timing data to text, feed it to a home-brewed python/perl script to create a chapter file, and then use the mp4v2 tools (mp4chaps specifically) to recreate the chapter information in the final m4a or m4b file. Be sure to keep sub-second accuracy as even half a second error over a bunch of chapters can add up to be annoying.

For the codec, I'd recommend the qaac tools which use the Apple AAC codec to encode and deliver results which, according to most listening test, are better than neroaac and other aac codecs.

[nu774]

Try something like the following:
qaac --he --cvbr 48 --concat *.mp3 -o output.m4a
This will do what you want, including chapters for each track (both of Nero and QuickTime style).
You probably want to tweak "--he --cvbr 48" part for your needs.

[Yamcha]

I use an abandoned program called Aaresoft Mp3 Merger from Pickmp3 inc (Dead Website) It can merge from 2 to 9999 MP3 files into one MP3 file.
I prefer Nero's free AAC encoder/decoder mp3-aac conversion.

[AlanHK]

If those are "plain" MP3 files and they have the same sample-rate, they can be combined simply via COPY command:
COPY /B file1.mp3 + file2.mp3 + file3.mp3 combined.mp3

You should never do that. It might give you a playable MP3, but the headers will obviously be from the first file and have the wrong duration. Many audioplayers will choke on it, especially iPods, and probably other Apple products that expect you to have perfect files bought from iTunes, and just stop at the time indicated for the end.

There are tools you can fix this with, but better to just make it right to begin with. MP3DirectCut can merge up to 50 files losslessly.
MergeMP3 (https://www.shchuka.com/software/mergemp3/) is freeware that can join as many as you like.
Most other generic audio joiners reencode everything and so degrade the audio, and also take much longer.

Yes, putting in chapter markers is definitely a good idea.
Unfortunately, I don't know of any tool that does this automatically while merging chapter files

fre:ac does this, in the alpha version now.
Works very well, give it a folder of MP3s and it makes an M4B with chapters, chapter titles from the title tags of the MP3s if they have them.