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Slightly Hot Audio

Posted: Mon Mar 30, 2009 8:51 pm
by JohnKleban
I have an audio feed from a ceremony in which the priest's mic was just a touch hot in a few parts; I'd say 85% of him talking is great, but the other 15% is just a touch hot (frankly, still passable, not distorted or anything); but, is there anything in audio effects pack that can assist with this a little? Any recommended tweaks one has done that worked?

Thanks!!

Re: Slightly Hot Audio

Posted: Tue Mar 31, 2009 8:09 am
by videojim
I haven't really seen a good explanation of it, but in the envelope button there is a trick called "rubber banding" that would let you knock down the hot audio so it doesn't overrun on the signal. But there would need be someone who could explain how a bit better. I've seen this trick used in other editing systems to good effect, such as a sound you wanted to fade, not drop out. Rubber banding is a very useful tool for keeping audio signals in check.

Re: Slightly Hot Audio

Posted: Tue Mar 31, 2009 1:49 pm
by JPaul
You could use envelope to lower certain overmodulated segments.
1) Click on the problem audio track envelope, then envelope.
2) You may be able to tell from the audio graphic just where you need to lower the volume.
3) Insert new points before & after outside the offending volume (use range or position to move the points to just before and just after the audio you want to change).
4) Then, insert 2 more points within or inside the previous 2.
5) You now have 4 points, two of which are just outside of the area you want to adjust.
6) The 2 inside points can be placed adjacent to the front & end points, or a short distance away from them to fade in/out.
7) The 2 inside points are the ones that will be used to lower the volume. The outside points maintain the "normal" volume.
8) Create and play from the 1st outside point to see if it sounds right. Adjust as needed. Repeat for other areas.

I like to use this because it gives excellent control over just how the volume fades into and out of adjustment. You can also use this to lower a music track in order to hear spoken words for instance. Using the range option allows you to see & hear frame by frame to make precise adjustments. Note the once you use envelope, you will not be able to adjust volume in the normal way - however, you can always go back into envelope to make other adjustments. If you remove the scene from the storyboard, you will lose these adjustments unless you create a new scene that incorporates the new audio.

This is much easier to use than to explain. Others may be able to explain it better or I can give it another shot. Good luck!

Re: Slightly Hot Audio

Posted: Tue Mar 31, 2009 2:10 pm
by CasablancaExpert
John,

The two options for consideration within your Casablanca are in the Audio Effects Pack, Normalize and Max. Volume. I have primarily used Max. Vol in the past to bring up slightly lower volume of varying interviewees to a level that was consistent. Normalize can be set to a particular dB setting and it will bring your the single audio sample (or all audio samples in a specific track when using the Effects Track function) to that setting.
You can 'pre-listen' to the results if you like in the Audio Mix menu/s.

I have yet to try it, but two of our more experienced colleagues (Bobbie & Don) use the 'Levelator', which is a freeware program (for both Mac and PC). I believe they export their completed audio track (from Scene function) and then run it through this computer application which works like magic apparently. You can read more about it and download it here http://www.conversationsnetwork.org/levelator

Regards,
Chet

Re: Slightly Hot Audio

Posted: Tue Mar 31, 2009 2:48 pm
by CKNewman
John,

You might try Dynamic from the Audio Effects Pack. The instructions say:

Dynamic
Adjustment of volume differences. The Dynamic effect allows you to attenuate peaks
in the signal. Quiet sounds can be amplified or also suppressed. Imagine you have a recording
that is generally very quiet but at some point contains a loud bang.
You will not easily be able to make this recording louder without over-amplifying the
bang. But the Dynamic effect allows you to do this!

(I've used this to reduce the sound made by clergy as they tapped to the beat of a song on the lecturn! I'm not sure how well it would work with speech)

Rubber banding is a good idea, just remember that there is no way to zoom in on a portion of a sample you are working on. The way around this is to split the section you need to lower before you start - then the envelope window might only have a couple of minutes rather than a long scene.

Another way to lower the audio in the problem places might be to split the scene up to isolate the "hot" portions. Create a Silent Sample that is the same length as the problem clip you just split. Add it to an empty track and use it to lower the original. Add fades to smooth the transitions in volume. Make a scene so you don't loose your work!

Re: Slightly Hot Audio

Posted: Tue Mar 31, 2009 7:32 pm
by JohnKleban
Thanks for the tips guys, much appreciated and I'm saving this stuff for future use as well.

Re: Slightly Hot Audio

Posted: Wed Apr 01, 2009 5:40 pm
by jeffphilips
John,
Not sure what your level of experience is with video/ audio, but I am sure others can benifit from this tip.
Keep in mind that if the original recording is over modulated, there is nothing that can fix it. You may be able to turn down the volume, but it won't fix the over modulated audio. You said slightly hot, not sure if it was over modulated.
When setting your audio during a shoot, it should be set so the loudest part will not peak. I realize that during a live shoot when you are the camera op and audio/light tech, it is hard to monitor all perfectly.
What I do in those situations is set the audio levels lower then normal. I can always raise them in post and not worry about distorted audio.

Re: Slightly Hot Audio

Posted: Thu Apr 02, 2009 7:31 am
by CKNewman
Macrosystem audio software is very basic - it can adjust volume levels but little else for the situation you're dealing with. Howevah, you could start reading up on "clipped peak restoration". This is found in some of the PC and Mac audio software. Take a look at Sony's Sound Forge 9.0 with the Noise Reduction 2.0 effects. Version 8.0 may also have it. If you use it please let us know how it works!

Re: Slightly Hot Audio

Posted: Thu Apr 02, 2009 8:53 am
by CasablancaExpert
Keep in mind that if the original recording is over modulated, there is nothing that can fix it. You may be able to turn down the volume, but it won't fix the over modulated audio.
This is an important point you made Jeff and I couldn't agree with you more. It is important for all the other folks reading this thread to note that in Post (editing) you can sometimes affect or slightly fix audio but it is so much better to get proper audio levels during the initial recording.

That said, I offered the Audio Effects suggestions as John did say his audio was a tad bit high in spots and not distorted. There are some sophisticated software options (outside of Casablanca) to deal with these situations but as you pointed out, no real way of getting them back to great audio.

Regards,
Chet

Re: Slightly Hot Audio

Posted: Thu Apr 02, 2009 12:11 pm
by BobFoster
Craig, I have found that "Clipped Peak Restoration" in Sound Forge works pretty good for hot audio if it is not badly distorted. For important audio when I am set up in fixed location, I use a Shure FP-410 auto audio mixer with a sound limiter that prevents over modulation regardless of incoming sound level.