Concatenating mp3 files

I use Audacity and want to concatenate mp3 files with it.
There are instructions for that - import the (e.g. two)
files, click on the second, CTRL C, go to the end of file 1
and CTRL V, and export that. Even when I wipe the second
before exporting the concatenated top one, it turns out too
big. E.g. file 1, 12 Mb, file 2, 4 Mb, but the result is 22 Mb.

What am I doing wrong, or how should I do it?

--
Dieter Britz

In article >,
Dieter Britz > wrote:
>I use Audacity and want to concatenate mp3 files with it.
>There are instructions for that - import the (e.g. two)
>files, click on the second, CTRL C, go to the end of file 1
>and CTRL V, and export that. Even when I wipe the second
>before exporting the concatenated top one, it turns out too
>big. E.g. file 1, 12 Mb, file 2, 4 Mb, but the result is 22 Mb.
>
>What am I doing wrong, or how should I do it?

If you're using Audacity, then what's happening is that Audacity is
decoding (decompressing) the MP3 file when it loads then, turning them
back into normal audio samples. After you concatenate them, the
"save" operation is then re-encoding the combined file, at whatever
compression or bit-rate setting that Audacity is set up to use.

That's going to have two effects:

- You'll lose audio quality, compared to the original MP3 files,
because of the extra decode/re-encode step (decoding is lossless,
but the re-encoding step is lossy).

- The combined file size may be either more or less than the sum of
the two separate encoded file sizes, because Audacity's compression
settings are probably different than whatever did the MP3 encodings
of the original files.

A better way to do this is to use a tool which is capable of parsing
the MP3 data and catenating the two streams, without having to decode
and re-encode the audio. As far as I'm aware, Audacity cannot do this.

If you have a Linux system, you could use "mp3wrap" (Debian and Ubuntu
have it and it's probably available for other distributions as well).
It can combine the streams, and still preserve MP3 tagging ("crossing
the streams" isn't always bad :-) )

If you're using Windows there are very probably similar utilities
available.

On Sat, 04 Jan 2020 15:27:41 -0800, Dave Platt wrote:

> In article >,
> Dieter Britz > wrote:
>>I use Audacity and want to concatenate mp3 files with it. There are
>>instructions for that - import the (e.g. two)
>>files, click on the second, CTRL C, go to the end of file 1 and CTRL V,
>>and export that. Even when I wipe the second before exporting the
>>concatenated top one, it turns out too big. E.g. file 1, 12 Mb, file 2,
>>4 Mb, but the result is 22 Mb.
>>
>>What am I doing wrong, or how should I do it?
>
> If you're using Audacity, then what's happening is that Audacity is
> decoding (decompressing) the MP3 file when it loads then, turning them
> back into normal audio samples. After you concatenate them, the "save"
> operation is then re-encoding the combined file, at whatever compression
> or bit-rate setting that Audacity is set up to use.
>
> That's going to have two effects:
>
> - You'll lose audio quality, compared to the original MP3 files,
> because of the extra decode/re-encode step (decoding is lossless, but
> the re-encoding step is lossy).
>
> - The combined file size may be either more or less than the sum of
> the two separate encoded file sizes, because Audacity's compression
> settings are probably different than whatever did the MP3 encodings
> of the original files.
>
> A better way to do this is to use a tool which is capable of parsing the
> MP3 data and catenating the two streams, without having to decode and
> re-encode the audio. As far as I'm aware, Audacity cannot do this.
>
> If you have a Linux system, you could use "mp3wrap" (Debian and Ubuntu
> have it and it's probably available for other distributions as well). It
> can combine the streams, and still preserve MP3 tagging ("crossing the
> streams" isn't always bad :-) )
>
> If you're using Windows there are very probably similar utilities
> available.

Thanks! I just installed mp3wrap, didn't know it existed. Good stuff!

--
Dieter Britz

Dieter Britz > writes:

> I use Audacity and want to concatenate mp3 files with it.
> There are instructions for that - import the (e.g. two)
> files, click on the second, CTRL C, go to the end of file 1
> and CTRL V, and export that. Even when I wipe the second
> before exporting the concatenated top one, it turns out too
> big. E.g. file 1, 12 Mb, file 2, 4 Mb, but the result is 22 Mb.
>
> What am I doing wrong, or how should I do it?

It may be some of the (re)encoding parameters you are using
in Audacity are not as lax as the originally-encoded files.
--
Randy Yates, DSP/Embedded Firmware Developer
Digital Signal Labs
http://www.digitalsignallabs.com