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> Too Much Recording Volume
Vinod Saranga
post Dec 23 2007, 07:59 AM
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I recorded indoor band show recently.However the recorded volume is too high.It is distorted.Decreasing the volume doesn't help because waves tops are cut(Audio is clipped.).Is there any way to restore my recording or to reduce the distortion.

Thanks

This post has been edited by Vinod: Dec 23 2007, 08:38 AM


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Marcus Lavendell
post Dec 23 2007, 09:33 AM
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Sorry, Vinod! If the audio is clipped so much that it is distorted, then there's nothing you can do sad.gif


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Vinod Saranga
post Dec 23 2007, 11:53 AM
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QUOTE (lavendell @ Dec 23 2007, 02:33 PM) *
Sorry, Vinod! If the audio is clipped so much that it is distorted, then there's nothing you can do sad.gif
-Marcus

Yes Marcus sad.gif
I came across very powerfull declipping plugins but they can't help in very long clipped audios.

This post has been edited by Vinod: Dec 23 2007, 11:54 AM


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Marcus Lavendell
post Dec 23 2007, 12:15 PM
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Yes, those plug-ins are good for small pops but not when it is distorted.

But I guess a lesson is learned, right? Always check the volume/input level before you hit record, and also to put a compressor in there.


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Vinod Saranga
post Dec 23 2007, 12:52 PM
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Yes learnt. biggrin.gif
I knew what would happen.
Problem was that I was unable to monitor the levels as I have to focus on the Playing.I just recorded the show.
Thanks for your Ideas smile.gif


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Ivan Milenkovic
post Dec 23 2007, 02:31 PM
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When something is clipped it is actually NOT written down on a sound carrier. The software doesn't even have the information on how your band sounded like in those peaks that are clipped. Be careful next time, try find some monitoring earphones or a loudness meter.


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Vinod Saranga
post Dec 23 2007, 04:32 PM
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Thanks Ivan smile.gif


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Saoirse O'Shea
post Dec 24 2007, 06:26 PM
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It's a tough one Vinod.

If your individual signals are not clipped - ie its only the composite 'master' that goes red then drop the level of the master fader. That might bring the whole back in range - ie here you haven't clipped the input but have clipped the output summed buss. If it doesn't though and you're clipped at the input then you'll need more drastic surgery.

As already said the best answer is not to record hot - see the lesson on recording hot and too hot in the sub forum for more on this. However as that's too late then let's think about what you might be able to do. First you need to work with a wav or aiff file - mp3 is too compressed.

Equipment you will need as a minimum:


Full band Spectrum analyser.
Multiband compressor.
Mastering Harmonic EQ balancer.
Brick Wall Limiter.
Gate.
Low and high band pass filters.
High quality mastering monitors.
Summing Mixer.
Good AD/DC convertors (Apogee or better).


Digital clipping introduces a lot of complicated issues to an audio signal. Some of these are that, like Ivan says, you will get a truncated hyper-compressed signal. If you looked at the signal through a wave form spectrum analyser the top of many of the audio frequencies would be flattened off when clipping sets in. In addition to this you also will get some high end spectral harmonics in the signal that shouldn't normally be there. That's one reason why a clipped signal often sounds so harsh and toppy. Also you'd probably find that the signal is band limited to below 18kHz.

So as a minimum you'd need to have a full spectrum analysis to see what has happened. From there use a multiband compressor to try to put back some life in to the peaks that have been flattened. You may need to sidechain a gate on each band as when you increase the signal you may get the low frequencies to over emphasise and 'rush up'. You will be trying to put sound energy back into the signal and so you may well find that you will overshooting and ironically induce yet more distortion by upping the rms energy profile of the entire audio signal. So chances are you'll probably have to add a band pass filter and gate and a limiter to the side chain.

As an alternative/addition to this you could try a phase rotator on the signal to shift the flattened peaks across to other portions of the wave signal. This form of non-linear processing won't really get rid of the distortion but it will spread it out and might fit the recorded type of music. (It can work with some rock and grunge but not classical or jazz.)

In doing any of this you will need to add some wanted audio density to the signal - ie put in peaks and troughs across the portion that's flattened out - and get rid of some unwanted (the harminics). Adding here isn't ideal as the amount of compression on a clipped signal isn't uniform and you aren't likely to know what frequency peaks were clipped. All you can do is to use a good harmonic eq balancer and do it painstakingly by ear. Whilst your doing this you could also do something about reducing the effects of the nasty unwanted high end harmonics that have been induced. Harmonics woill appear at nice mathematical multiples in the spectrum - just be aware that some are meant to be there, the ones you need to attenuate are those induced by the distortion. Again you may need to now put the whole thing through a good brick wall limiter to stop any over emphasis.

Chances are by now that you will need to rebalance the stereo field. In reprocessing you will have changed the amount of gain in the channels and, assuming that you haven't recorded everything dead centre, you may well now find that the left/right/centre will be out of balance. If you had reverb on the original recording then you might find that the reverb is over emphasised on the centre channel. If that's the case attenuate it and put a small amount of reverb only on L/R.

There are a some mixing/mastering techniques there that can also help - adding 'air' to the mix, riding the gain levels and using both hard and soft knee compression and so on.

It may help btw to use a high end AD/DA system to do the following (Apogee Rosetta or better) and run the whole thing at high frequency to reduce any additional anti-aliasing distortion and where possible jitter correction. Once you're done then resample, or render, the whole thing at a lower bit rate (say 16 bit instead of 24) to force dither correction and add some noise to the signal - this, odd as it may sound, can help mask the distortion you get with clipping.

All of the above will take time, patience, a lot of effort and really needs good quality mastering equipment. Not easy and not ideal - chances are that no matter how well you do this it will not sound great. TBH it's easier, faster and you will get a better result by re-recording the whole take from scratch.

Cheers,
Tony


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Vinod Saranga
post Dec 26 2007, 05:41 PM
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Well explained Tony.
I tried.It seem to be working but need patience and time.
I will edit it when I get free time.
I can't think a way to thank you. smile.gif
Many thanks
Vinod

This post has been edited by Vinod: Dec 26 2007, 05:44 PM


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Saoirse O'Shea
post Dec 26 2007, 07:20 PM
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NP Vinod - and best of luck with it as well mate. Not something that is easy to correct but give it a go when you have enough time and you never know smile.gif . If you need to talk about it you know where to come smile.gif wink.gif .


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Cranesong Avocet II Monitor Controller, Dangerous Music Liasion Insert Hardware Router, ATC SCM Pro Monitors, Lavry Black DA11, Prism Orpheus ADC/DAC, Gyratec Gyraf XIV Parallel Passive Mastering EQ, Great River MAQ 2NV Mastering EQ, Kush Clariphonic Parallel EQ Shelf, Maselec MLA-2 Mastering Compressor, API 2500 Mastering Compressor, Eventide Eclipse Reverb/Echo.
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