Urgent problem with VS Pro x7 audio speed/time lapse issue

[dcdenizen]

MP3 Audio Properties of the narration file

audio properties.png (5.17 KiB) Viewed 5404 times

Could I please ask for urgent help with an audio issue I have never encountered before? Using VS Pro x7 on a PC (Windows 7, 64-bit). I imported an mp3 file of narration from a reliable source. It played perfectly fine, until I adjusted clips using the speed/time lapse function. It performs the task, but there is a problem with the audio playback. I'm not an audio expert, so I am not sure if this nomenclature is correct, but I would call it a phasing issue -- in that it bounces back and forth erratically between my speakers. I tried converting the mp3 file into a few other formats (.wav 16 and 32-bit, and aiff), but the outcome doesn't change. I have Audacity, but am not knowledgeable enough about various audio parameters to know what settings to try. Could you please help? Thank you.

UPDATE: I converted the mp3 file from stereo to mono in Audacity. That seems to have alleviated the "phasing" problem. But I would be interested to know a possible reason behind this glitch, and if there are settings I could try to adjust in the future without having to downgrade from stereo to mono. Thank you.

[TroyTheTech]

If I may pop in, what an interesting issue...
I did not even notice this until I specifically tested for it just now.
I guess I never really used the audio Speed adjustments in this way...

I tested this with MP3 then an 'uncompressed' WAV (WAV format is always lightly compressed, as is all digital audio in any format, due to conversion from analog to digital, although some formats are 'lossless') and when output to WAV or MP4 (AAC) it doesn' t matter, this effect (artifact?) occurs.

Nice find!

For those wondering, it seems to 'self-widen the stereo range' and is odd sounding, sort of like a 'reverse Joint Stereo phasing'...

I made a small sample and uploaded the' audio-only output', here:
https://clyp.it/vkbl0uzj
(japanese audio with some flute sounds, the effect (and some compression artifacting) can be heard throughout but is most obvious beginning at about the 0:06 time mark

I am experienced with computer systems but not specifically audio media... If anyone knows the technical details of what is occurring - and how to fix it - feel free to chime in!

[dcdenizen]

I never received a response to my question from any of the mods. Maybe you'll have better luck.

[TroyTheTech]

I never received a response to my question from any of the mods. Maybe you'll have better luck.

I just saw your use of the word 'urgent' odd that my brain did not 'see it' the first time - perhaps that is why it was unfortunate that noone replied... perhaps noone knows what this issue is

I will try researching it on my own (for fun!) but I cannot guarantee a quick reply or answer to what it is, sorry

[lata]

Hi

Sorry your post went unnoticed, certainly I missed the post.

Not sure what to think, first I would suspect using MP3 audio, the lame codec used for mp3 does cause some issues for video editors
We would advise converting to Wav, but you say wav files also show the same effect.

I have tried using the library samples and applying Speed Timelapse, the playback seems ok, or does it only show after rendering?

I assume you are using Speed /Timelapse to correct audio sync?
So what level of Speed have you applied.

If you view the problem file in Sound Mixer the volume levels show when playing in project playback, do those levels reflect the audio problem.

[TroyTheTech]

Hi

Sorry your post went unnoticed, certainly I missed the post.

Not sure what to think, first I would suspect using MP3 audio, the lame codec used for mp3 does cause some issues for video editors
We would advise converting to Wav, but you say wav files also show the same effect.

I have tried using the library samples and applying Speed Timelapse, the playback seems ok, or does it only show after rendering?

I assume you are using Speed /Timelapse to correct audio sync?
So what level of Speed have you applied.

If you view the problem file in Sound Mixer the volume levels show when playing in project playback, do those levels reflect the audio problem.

If I may pop back to answer some of this (I am finding this phenomenon interesting - but I do not want to "step on anyone's toes" so please let me know if I should withhold my interjections..);

- Yes a WAV format audio file produces the same odd 'widening' (the only way I can describe what I am hearing), in my test, I recorded into WAV format
- I tried a small amount of Speed adjustment (120%), but this 'artifacting' occurs at different speed changes as well (tested 200%, tested 50%, etc)
- Interestingly, it does in fact show up on the Sound Mixer monitoring. Here is a GIF of the stereo WAV file, after changing the Project Properties to 6-channel audio (Surround), it is clearer when viewed Full Size of course:

The odd-sounding audio playback artifacts seem to get picked up by the application as Surround Sound signals (the "V" shape indicating the rear channels are even being used more than the front for a very short time).

...I have no idea why, but I am finding this odd effect fascinating!

[BrianCee]

All input is welcome Troy - please feel free to add to any topic which you have knowledge or interest in

Interestingly I see a slightly different image (though still showing the same effect) when viewed full size

for other users - you can do that by clicking on the image in Troys post




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[lata]

Hi
Dcdenizen is using a video with stereo sound, so why are we trying to test surround sound
Depending on the final output settings would influence whether surround sound is available?
I suspect stereo will be used.
The original file uses 41Khz where as video studio defaults to using 48Khz, I assume the sound file is being added to a video clip, that would require audio sync, the op does not make that clear.

I would try using Audacity to convert the Mp3 to Wav 48Khz

I am no expert in audio and my pc is not set up to listen to quality audio so struggling to hear any problems with my tests?

[TroyTheTech]

Hi
Dcdenizen is using a video with stereo sound, so why are we trying to test surround sound
Depending on the final output settings would influence whether surround sound is available?
I suspect stereo will be used.
The original file uses 41Khz where as video studio defaults to using 48Khz, I assume the sound file is being added to a video clip, that would require audio sync, the op does not make that clear.

I would try using Audacity to convert the Mp3 to Wav 48Khz

I am no expert in audio and my pc is not set up to listen to quality audio so struggling to hear any problems with my tests?

I was the only one testing with Surround Sound, and it was only because the odd effect sounds similar to the result of when a 'stereo widen' filter is placed on an audio clip (with any editing program). It interestingly came up as using the Surround channels, that is the only reason why I shared that. I apologize if it confused anyone.

The effect is not noticeable to everyone, which is interesting to me as well. I have played this phenomenon for a few people and only some have heard it, some have not.

If I have time, I will try to 'accentuate' the odd effect that is occurring, to help others notice it.