[FFmpeg-user] File metadata in m4a causing player problem?

[Moritz Barsnick]

Hi Budgie,

On Sun, Oct 20, 2019 at 09:56:40 +0100, Budge wrote:
> I have a set of m4a audio files which I can play but on which the
> progress bar does not work.  If I select anywhere along the progress bar
> playing starts again from the beginning.

In which players does seeking not work? In all of them? Which did you
test?

How were there files created? Are they arbitrary files, or did you
create them with ffmpeg?

Can you provide some of these files?

> The only difference I can see when using ffprobe to examine the metadata
> is that files which have a creation_time set have a non functioning
> progress bar problem.

That may be a symptom of their creation, but not the actual root cause
for your issues.

> What I wish to do is remove the tag:
> creation_time   : 1970-01-01T00:00:00.000000Z

ffmpeg certainly didn't create this by itself, but I understand that's
not what you're trying to say. ;-)

> I confess using ffmpeg to achieve this, if indeed this is the correct
> tool, is well beyond my ability and I am seeking help here.

Even though I don't believe that is the root cause, I was going to explain
to you how to strip metadata using ffmpeg. But it turns out that, when
remuxing, ffmpeg doesn't actually copy the creation_time. So all you
have to do may be:

$ ffmpeg -i input.m4a -c copy output.m4a

You can then test the output file.

The resulting file may also be fixed for other reasons than the
metadata, e.g. reconstruction of some index or something like that,
which the original may be missing. (Guessing here - just go try.)

Hope this helps,
Moritz