Audio disappears in middle of audio track

[JudyArielle]

i tried exporting it into wav and what you get is a flat line and silence. i'll get back to you with more details when i get back to the class and talk to the kids about it more specifically.
again thanks much for the brain power on this.

[steve]

The difficulty that we are having is that it seems to be a problem that none of us has come across before, and we can't reproduce the problem.

The fact that you have the same problem on multiple machines makes me wonder if you have a slightly messed up installation of Audacity which has been cloned to the other machines.

Is it always the same machines that have the problem?
Is it always the same users that have the problem? (do the students always use the same computers?)

If the answer to both of these is "yes", then try moving your students to different machines (this may not be possible if they are mid way through a large project) - if the same machines still have the problem, then it's to do with the specific machines, but if the problem moves with the student then it is something they are doing and we will need to find out what that is.

let's say it's a track off of a music cd that had been saved onto the computer in a wav or aiff format- and that came from a single source- that aup file will have audio missing from the middle of it; or perhaps the aup track will begin with a minute of the song and then the rest of the song cannot be heard.

And I presume that the source file plays fine - that rules out lots of possibilities.

If that is what you are saying, and in this example no sound came out from 2 mins to 4 mins, if you then stop Audacity and try playing from 3 minutes into the track, will it play or not?

hmmm.... i'm not sure if i've tried that or not. i think i might have done that just checking out along the track and i feel that it is consistent which part of the track is silent and which part has audio.

I'm betting that it is consistent, but please check this.

i tried exporting it into wav and what you get is a flat line and silence.

Whereas before exporting, it was NOT a flat line, but WAS silent?

Have you managed to reproduce the fault yourself?

[kozikowski]

<<<i tried exporting it into wav and what you get is a flat line and silence. >>>

Which gave Audacity a chance to catch up the waveforms with reality.

<<<Whereas before exporting, it was NOT a flat line, but WAS silent?>>>

Before exporting, the symptoms were almost exactly those of having moved a clip and not telling Audacity what you did. The show goes silent and you get "phantom" waveforms. Exporting the show as a WAV gives Audacity a chance to redraw the waveforms and everything comes out even again--except we still have silence in the wrong places.

The killer is that this happens within a clip and parts of the clip survive. The most likely answer is still a damaged clip somehow with a minor in computer hardware error, and now that I've slept on it, a damaged third party plugin.

"I got this cool vst plugin from the internet and I shared it with my friend on the other side of the room."

Koz

[JudyArielle]

thanks for all your good problem solving on this one. i will get back to you after i am able to follow up with all your suggestions and let you know what i discover.

[steve]

For information - this problem can be reproduced if you delete some of the temporary .au files.
Makes me wonder if someone has "cleaned up some unnecessary old temp files".

[kozikowski]

See earlier in the post. I advanced that idea and the general consensus is no. The students went to export their show and there were pieces missing in some very awkward places. Two different students, as I understand it. The rest of the class was OK.

The frightening possibility is that the computer got it in its craw to damage the files by itself. That is most unusual, but not unheard of if you violate some Mac rules--or there is disk damage or memory damage.

Koz

[Clayton]

I have had the same trouble as Judy: after doing some editing on a single track, all of which came from one aiff file, the audio would stop though the wave on the screen continued as normal, though the meter is not registering any sound. It can't have anything to do with multiple sources the program is coordinating because the track was imported whole from one source--an aiff file on a CD which was recorded whole. I was later able to successfully edit and burn the track using another program, so there was nothing wrong with the original.
One other feature of the phenomenon is that if I zoomed in to the wave, it would disappear in the soundless portions, and then reappear on zooming out, but it didn't change the silence.

Clayton

[kozikowski]

<<<One other feature of the phenomenon is that if I zoomed in to the wave, it would disappear in the soundless portions, and then reappear on zooming out, but it didn't change the silence.>>>

Ok, well that, at least, is old news. Screen graphics are handled completely separately from the sound. If you delete or damage one of the first two AU files in the _DATA folder, you will find that either the left or the right waveform will vanish. I'm not shocked that some damage will happen to the show and the blue waveforms lose contact with reality in whatever form that takes.

The problem is that damage like this can occur by either damaging the original sound clips, or damaging the contents of the _DATA folder.

I'm thinking through that as I type it. That's not true. You can also have damage to the AUP project file. That one's the traffic cop. That one is responsible for coordinating the activity of the edit.

Projects work by keeping a laundry list of your theatrical script. If your show calls for deleting the middle minute of a three minute cut, Audacity doesn't take a digital machete to the sound file. It just writes a little note to itself stuck to the refrigerator door that the next time somebody tries to play the three minute cut, play around the middle minute--jump from the end of minute one to the beginning of minute three. If you select UnDo, you'll never guess what happens to the note. It "forgets" to do the edit.

That note on the refrigerator door is the AUP file. You can read it with any text editor. If the show gets just a little too complicated to describe the work, then Audacity starts creating AU files, numbers three through whatever (first two are graphics). I have no idea how Audacity decides when and if to create these files, but they do two things. They make Audacity enormously faster and more efficient than it would be with the Machete Method and they make it impossible to explain Projects to people. As a side effect to number two, they make troubleshooting a nightmare.

Projects also make the end of an undamaged edit session a nightmare. We need to email/ftp the show to the client in Chicago. It's probably here somewhere in the AU files, right? No, not really. the first time the show becomes one single sound file is the first time you export it that way. Until then, it will remain a cloud of Project files on your hard drive.

"Which will bring us back to doe" (Julie Andrews--Sound of Music--1965).

Something in the cloud broke.

Koz

[steve]

Projects work by keeping a laundry list of your theatrical script. If your show calls for deleting the middle minute of a three minute cut, Audacity doesn't take a digital machete to the sound file. It just writes a little note to itself stuck to the refrigerator door that the next time somebody tries to play the three minute cut, play around the middle minute--jump from the end of minute one to the beginning of minute three. If you select UnDo, you'll never guess what happens to the note. It "forgets" to do the edit.That note on the refrigerator door is the AUP file.

Very nice explanation koz

Screen graphics are handled completely separately from the sound....
If the show gets just a little too complicated to describe the work, then Audacity starts creating AU files, numbers three through whatever (first two are graphics).

That's not exactly correct - the .au files are created and numbered by Audacity as needed by some mysterious method known only to itself. The first two files can also contain audio data. Graphical data can also be contained in .au files other than files 0 and 1.

When a new project is started, files are created in the temp directory as needed, but if an existing project is opened, the files are written directly into the project (not sure what happens if you open a project from a CD, I guess it would default back to the temp directory, but not tested that).

If any of the required .au files are missing, then when Audacity opens it will show an error message to say that it cannot find them. If tracks are deleted from a project, the data files are not deleted, even when the project is saved, but unused .au files will usually be deleted (but not always) when Audacity is closed.

I'm thinking through that as I type it. That's not true. You can also have damage to the AUP project file.

Certainly if the .aup file is damaged, it will mess up the project, but I doubt that this is the problem as I would expect this to cause other errors and error messages.

The .au files can not be missing without generating an error on opening the project, but if something is causing .au files to be empty files, then that will produce these symptoms.

I've just done a couple of test:
1) I deliberately changed the data in an .au file (not file number 0 or 1) and the result was that the corresponding part of the recording was silent, but also the waveform was corrupted.
2) I deleted the contents of an .au file (not file number 0 or 1) making it a zero byte file, and the result was the corresponding part of the recording was silent, but the waveform was unaffected.

Going back to the original problem, it may be worth having a look to see if there are any zero byte (or very small) .au files in the project. (note that it is normal for the last .au file to be smaller than the others).

[kozikowski]

<<<a zero byte file, and the result was the corresponding part of the recording was silent, but the waveform was unaffected.>>>
<<<see if there are any zero byte (or very small) .au files in the project.>>>

Excellent detective work. How do I get that in the course of a normal edit--on a Mac, which doesn't normally have virus or stability problems? And how do you afflict only two people out of the whole class?

I'm going back to my original assumption that someone got a "really cool [malformed] VST plugin" downloaded from the internet and shared it with Best Bud Johnny across the room.

Koz