[Ardour-Users] Audio files imported with an extra gap that doesn't exist on disk

[James Harkins]

---- On Sat, 28 Mar 2020 10:06:08 -1000  <ardour-users-request at lists.ardour.org> wrote ----
> From: Robin Gareus <robin at gareus.org>
> On 3/28/20 10:14 AM, James Harkins wrote:
> > Hi,
> What file format it it?
> Can you share the file and/or provide information about the specific
> file (e.g. sndfile-info /path/to/the_file.wav)?
> 
> Looking at Ardour's waveform display there is no gap. The part that
> you've highlighted is not silent, only very low volume.

It is silent. The original files were recorded in SuperCollider as stem tracks. There is no mic or ADC/DAC in the signal chain up to this point -- "silent" really means 0.

> Could it be that there is some meta-data in the file that specifies a
> start-offset, that is ignored by Ardour?

Unlikely.

I've just confirmed that the following sequence of steps reproduces the problem:

1. I recorded audio files (in SC -- doesn't matter where). I also normalized them in Audacity and exported to a different location, but I think this doesn't matter. I didn't do any trimming at this stage.

2. Imported the files into a new Ardour project.

3. Deleted the clips from the tracks.

4. Reopened the files in Audacity (separate tracks of the same project). Used sync-lock tracks to trim them so that the audio content starts at the bar line.

5. "Export multiple" overwriting the files.

6. Dragged the overwritten files (with the same name and path) into the Ardour project.

At this point, Ardour is using the *old* file contents (waveform display and sound). The most likely explanation is that Ardour believes it has already imported those files, so it must be using cached content without verifying whether the file changed or not.

Then, for fun, I quit Ardour (saving the project) and reopened the project. The waveform display still reflects the old files, but -- the tracks are silent!

Finally, if I rename the files and reimport into Ardour, all is normal.

I can understand why you usually wouldn't want users to edit, externally, the contents of audio files used in a project. But I had expected, when importing a file, that Ardour would update everything about that file/path -- especially if all references had been removed earlier. That's not unreasonable: I'd presume that the user has no need to drag the file in again, unless something had changed -- so, if the file is being dragged in again, for safety, you should check that it's really the same. (Whereas, Ardour seems to presume that audio files are fixed entities.)

In any case, now I know -- the rule is, when editing externally, always make a new version of the file with a different name.

hjh