• Concatenating mp3 files

    From Dieter Britz@21:1/5 to All on Sat Jan 4 12:55:58 2020
    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

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  • From Dave Platt@21:1/5 to dieterhansbritz@gmail.com on Sat Jan 4 15:27:41 2020
    In article <quq20u$su2$1@dont-email.me>,
    Dieter Britz <dieterhansbritz@gmail.com> 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.

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  • From Dieter Britz@21:1/5 to Dave Platt on Sun Jan 5 14:03:46 2020
    On Sat, 04 Jan 2020 15:27:41 -0800, Dave Platt wrote:

    In article <quq20u$su2$1@dont-email.me>,
    Dieter Britz <dieterhansbritz@gmail.com> 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

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  • From Randy Yates@21:1/5 to Dieter Britz on Sun Jan 26 02:58:00 2020
    Dieter Britz <dieterhansbritz@gmail.com> 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

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