Problem with noise at beginning of Export using Envelope

[steve]

Do you use "Soundflower" (it's a program).

[syvjeff]

No on the use of Sound Flower.

In the case of the file I sent you.

1. Voice Recorded in a production room using Audacity 1.3 on Win XP and an ASI Sound Card on the way in. Voice files don't have an issue.

2. Music is an MP3 file from a production house ripped years ago on to my hard drive. In this project, I did 26 different commercials using this music and the only time it would "crackle" would be when I would do a fade down to voice over.

Jeff

[steve]

I've come across a similar issue to this, which was also on a Mac. This is a very curious but distinctive type of distortion. Unfortunately in the previous case the user apparently gave up on the problem so we never did find out what the cause was (though something to do with Soundflower was one possibility, hence my question). Hopefully you will be able to stay with us long enough that we can get to the bottom of this issue (I'm assuming that it is the same issue). This may take a bit of time to track down, but I very much hope that we are able to do so.

What I think is happening is that there is some inaudible data corruption in one of the tracks, and that when that track is "rendered" the corrupt samples are "corrected" by Audacity to create samples that are very close to zero, and that it is those "zero" samples that create rapid clicks.

In your WAV file there are clicks at regular intervals of exactly 792 samples. We first need to identify where they have come from.
The more you can tell us about the occurrence of this problem the better.

Has this problem occurred in more than one Audacity project?
If so, other than the use of "Envelopes" what are the common factors?
Do they all involve mixing a live microphone recording with an MP3 music track?
Could it be related to one particular music track?

[syvjeff]

Hi Steve - I'm a patient man and a big believer in this project since I've been using Audacity for about 6 1/2 years. To be blunt, I caught this issue before and do to just being buried at work didn't have the time to post or work over this bug. So today after listening to a series of spots produced for a local client, it really caught my ear and everything pointed to the use of an envelope on this and another spot in the batch.

I don't know if you saw my previous post too, I was able to take the original files aup and all and open on a Windows machine running Audacity 1.03, export out an MP3 and WAV without the issue.

Now with all that said, how about this......I will go through previous projects with different voices and music and see if I find an exported file with the same issue and research the files and affects (envelope tool used) in them. If you are interested, I'd be glad to take this off board, create a shared Dropbox folder for you and just email back and forth.

Jeff

[steve]

I don't know if you saw my previous post too, I was able to take the original files aup and all and open on a Windows machine running Audacity 1.03, export out an MP3 and WAV without the issue.

Yes I saw that.

What I really want to see is a project just before the problem appears.
One way to get that is if you spot the problem before you have closed the project, then you will be able to Undo the last step that caused the problem to appear, and then use "File > Save Project As" and save the project with a new name. You should then be able to open that saved project and with a bit of luck the probably will be repeatable by applying the "final step". Do you have a project that you can do that with? Do you follow what I mean?

[Gale Andrews]

I don't know if you saw my previous post too, I was able to take the original files aup and all and open on a Windows machine running Audacity 1.03, export out an MP3 and WAV without the issue.

Yes I saw that.

What I really want to see is a project just before the problem appears.

Precisely. I might be able to help by testing on Mac (Steve does not have a Mac). But I don't see at the moment why this should be platform-specific. The other problems on Mac (either allegedly cured by export or caused by it) have sounded much more obvious than this.

I don't know if it's because I'm middle aged but I can hear absolutely nothing wrong on Windows 7 or Mac with "Education Savings Short wav file.wav" where the voice comes in, even on headphones. I can hear faint crackle at the start. If I select from zero to 1672 samples (before the visible waveform starts) and amplify to 0 dB, there is an explosive bang at the end of the selection. Is that what you mean, and do the clicks occur only where you start the fade out? Which is the first sample in "Education Savings Short wav file.wav" that has an example of a click?

Which "High-quality" dither setting is worst and best? What happens if you change high-quality dither to "None"?

And what happens if you use Effect > Adjustable Fade instead of Envelope Tool?


Gale

[syvjeff]

Hi Gale and Steve - I decided to try to have this issue rear it's ugly head again with the use of just wav files for voice and music and of course, cannot get this to happen again. I'm just wondering if it's an issue of using compressed files like the sample I gave you where the music came from an mp3 file. I'm going to keep on doing what I do and see if it happens again and immediately share a file showing it.

I still believe it's using the envelope tool though at the beginning.

Jeff

[Gale Andrews]

I decided to try to have this issue rear its ugly head again with the use of just wav files for voice and music and of course, cannot get this to happen again.

Some of the other users reporting noise have said the noise occurs where there is empty space in at least one of the tracks rather than audio or silence. Examples might be if you are working with clips that have been dragged apart in the track so they have white space in-between, or if you had two tracks starting at time zero but dragged one of them to right with Time Shift Tool.

Is this relevant to you?

I'm just wondering if it's an issue of using compressed files like the sample I gave you where the music came from an mp3 file.

It's possible the music source file is corrupted in some subtle way, but I would assume that corruption is not specific to MP3. Audacity will expand MP3 to PCM in any case.

If this happens with multiple MP3 files, do those files come from the same source?

I'm going to keep on doing what I do and see if it happens again and immediately share a file showing it.

Thanks for keeping your eye open. Ideally it is a project we need (AUP file, _data folder and use File > Check Dependencies to copy in any imported WAV files if dependencies are shown).


Gale

[DunLaoghaire]

Hi Gale,

I am having a similar issue to this, and your response regarding Time Shift is relevant to me.

I am using Audacity 2.0.3 on a MacBook Air running Mac OS X Lion 10.7.5 and am importing tracks from my iTunes library, adding voiceovers and fading into other tracks, so I am importing 3 or 4 different m4a files, then time shifting them and using envelope to fade.

Everything sounds fine in the edit screen but when I mix and render I get static for the first 6 seconds every time.

Is there a solution for this?

Thanks so much,
Michelle.

[Gale Andrews]

I am having a similar issue to this, and your response regarding Time Shift is relevant to me.

I am using Audacity 2.0.3 on a MacBook Air running Mac OS X Lion 10.7.5 and am importing tracks from my iTunes library, adding voiceovers and fading into other tracks, so I am importing 3 or 4 different m4a files, then time shifting them and using envelope to fade.

Everything sounds fine in the edit screen but when I mix and render I get static for the first 6 seconds every time.

Is there a solution for this?

I don't think we understand the cause of the problem or why it only gets reported on Mac.

If you don't use Envelope Tool, does the problem still occur after Mix and Render?

Does selecting from the start of the offset clips to time zero then Generate > Silence before you Mix and Render help?

Do the tracks say 16-bit or 32-bit? If 32-bit, does the problem go away when you export? This assumes in the Audacity Quality Preferences that you have High-quality Dither turned on (not on "None").

Can you post a project like Steve suggested, where you undo the step that caused the distortion, then File > Save Project As to a new name in that state, so we can perform the step in the project that causes the distortion?


Gale