[nmglug] ffmpeg guidance, please to convert m4b to mp3

[Holly Grimm]

LeRoy,
If you have timestamps, I would try these commands and see if they work for
you:

Begin at 0, with a duration of 1214 seconds:
ffmpeg -i audiobook.m4a -t 1214 -c copy chapter1.mp3

Begin at 20 minutes and 14 seconds, with a duration of 1214 seconds:
ffmpeg -ss 00:20:14 -i audiobook.m4a -to 1214 -c copy chapter2.mp3

https://trac.ffmpeg.org/wiki/Seeking for more details

Holly

On Wed, Nov 30, 2022 at 10:06 AM LeRoy Diener <leroy at choosetherightside.com>
wrote:

> To Wayne and all:
>
> The .m4b file is not corrupted. The 11hr file plays flawlessly in VLC and
> SMplayer. The first 1hr loads correctly in Audacity, but only as the
> truncated portion of the larger file. I found that others had a similar
> experience, as at https://forum.audacityteam.org/viewtopic.php?t=79754
>
> I'm guessing that the issue for Audacity is that the .m4b file includes
> some encoding which points to a .cue file which has the timestamps for the
> chapters. Here are snippets of the .cue file:
> TRACK 1 AUDIO
> TITLE "Chapter 01"
> INDEX 01 0:0:00
> TRACK 2 AUDIO
> TITLE "Chapter 02"
> INDEX 01 20:14:56
> ...
> TRACK 19 AUDIO
> TITLE "Chapter 19"
> INDEX 01 661:19:09
>
> My end objective is to break the 11hr file into smaller files, ideally the
> chapters of the audiobook.
> I'm not sure what is the best workflow for this. Here's one idea. If I can
> convert the .m4b file to a .mp3 file, then I can edit it in Audacity. It
> might be even easier if I can use ffmpeg to split the file into chapters.
> I would be happy to have the chapter files in .m4b format (unconverted). I
> just want to end up with files that are not so long.
>
> Wayne, thanks for your ideas. I have not yet tried using the nitrag
> script. I'm not sure how to do that, and I'm being cautious, asking for
> guidance.
>
> I'm still unsure about how to proceed.
> LeRoy
>
> --
>
> There is something glorious birthing within all of us.
> I am the Love of God, no matter what.
> BSA
> LeRoy Diener
> 213-LEROYIZ
> 213-537-6949
> https://leroydiener.com
>
> On Tue, 2022-11-29 at 15:32 -0800, Wayne wrote:
>
>
> If it can't be opened correctly by Audacity, is it possible the file is
> corrupted somehow?
>
> Do you really want the results in separate chapters, or is a single
> non-chaptered file okay? ffmpeg would be a very simple command-line if you
> wish to write to a single file. If you need to separate by chapters, did
> you try using the nitrag script?
>
> BTW, most video/audio editors use ffmpeg or one of it's components as it's
> engine. It is extremely powerful.
>
> Wayne
>
>
> On 11/26/22 1:16 PM, LeRoy Diener wrote:
>
> Hi NMGLUG folks,
>
> I would like to convert an audiobook .m4b file (probably with chapters in
> metadata) to .mp3 files split into chapters.
> I'm trying to learn how to convert files.
> I looked at https://ffmpeg.org/ffmpeg.html but it gets overwhelming.
>
> I'm not sure what the best approach will be.
> I also found https://github.com/sandreas/m4b-tool where the author
> references https://github.com/sandreas/tone
> Additionally, I found this script from nitrag
> https://gist.github.com/nitrag/a188b8969a539ce0f7a64deb56c00277
> Other options appear in
> https://www.videoproc.com/media-converter/m4b-to-mp3.htm
> Indeed, my first idea was to import the .m4b file into Audacity to do the
> conversion. Unfortunately, it doesn't import correctly into Audacity.
> I'm able to play .m4b file in VLC and SMplayer. It seems like it's
> possible to use VLC to do the conversion with some help from ffmpeg, though
> maybe not a great option.
>
> Any thoughts?
>
> Thanks,
> LeRoy
>
> --
>
> There is something glorious birthing within all of us.
> I am the Love of God, no matter what.
> BSA
> LeRoy Diener
> 213-LEROYIZ
> 213-537-6949
> https://leroydiener.com <https://leroydiener.com/>
>
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