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Does this master contain clipping?

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Does this master contain clipping?

Postby soundwichman » Fri Dec 21, 2018 8:20 pm

Hi all,
I recently employed somebody to do mastering of my tracks, and heard some subtle clippings in the result, so I looked into my DAW to see how the waveform looks like.
The top stereo waveform is the mastered version, the bottom one is the premaster:

Image

I know that limiters are sometimes used in mastering, but is the result I presented above normal or should I change the mastering engineer?
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Re: does this master contain clipping?

Postby Jack Ruston » Fri Dec 21, 2018 9:56 pm

Hard clipping is very common in mastering. It's certainly a genre dependent thing, and it shouldn't be glaringly obvious, but they will often clip the returning A to D in their hardware chain. It can be a useful way to add further limiting on the right material, or it can be overdone and ugly, or it can be wholly inappropriate.
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Re: does this master contain clipping?

Postby CS70 » Fri Dec 21, 2018 9:58 pm

Yes these flat areas look like digital clipping - the converters producing uniformly the max sample value. What matters though is what you hear: if (especially on headphones) you hear, small annoying scratchy sounds, it’s not that great..
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Re: does this master contain clipping?

Postby soundwichman » Fri Dec 21, 2018 10:23 pm

thanks for your answers, Jack and CS70!
yes, when I looked through the waveform and noticed many places were the signal seems to be clipped. I don't notice most of them while listening which I guess is fine, Jack, but there are few places where I do notice a soft scratchy sound.
I attach some short WAV samples of where it happens:

https://drive.google.com/open?id=1gFjzg ... E8vFJyrr6D
https://drive.google.com/open?id=10ksd- ... 0t0eH8BLtW

The first one is more obvious. I was doubtful about the second one (there's a slight something at the higher frequencies on the hit of the kick), but now I'm more convinced it's a master with a defect.
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Re: does this master contain clipping?

Postby James Perrett » Sat Dec 22, 2018 2:11 am

The first sample has obvious distortion on the guitar but I couldn't really hear any clipping on the second sample.
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Re: does this master contain clipping?

Postby Jack Ruston » Sat Dec 22, 2018 5:24 am

It's not a defect as such - it's a deliberate technique on the part of the ME to make the track louder. Some would say it shouldn't be common practice, but this is a situation that we all need to take some responsibility for. We've chosen masters on the basis of raw loudness for decades, and now these engineers feel that that's their only avenue for approval. Even with the recent move towards normalisation, this is still very much a thing.

Either way, you can hear it, you don't like it, and they should be willing to do a revision without it.

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Re: does this master contain clipping?

Postby Martin Walker » Sun Dec 23, 2018 5:25 pm

Jack Ruston wrote:Either way, you can hear it, you don't like it, and they should be willing to do a revision without it.

I agree with Jack here - you can see and hear something that you don't like, and which is due to an artistic decision taken by the mastering engineer. It's perfectly possible to achieve higher final levels in a track without resorting to digital clipping.

Explain what you can hear and where, and ask politely for a revision - hopefully the ME will at the very least be impressed that you can hear these artefacts and agree that you have a perfect right to object to them in your track.


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Re: does this master contain clipping?

Postby Guest » Sun Dec 23, 2018 5:53 pm

I agree with the other posts here but it reminded me of a recent article on the iZotope website, so maybe it was not noticed, or even deliberate:

"I’m hearing more artifacts in the vocal than before. Are you? If so, here’s another question: Can we chalk this up to the popular, bedroom production SoundCloud rappers—or has it really been a long time coming? I think it’s the latter. Indeed, glitches and artifacts have been increasingly acceptable in the vocals of popular mixes. These can be a result of tracking straight through Auto-Tune for effect, among other issues."

Here is the full article:

https://www.izotope.com/en/blog/mixing/top-5-pop-mixing-trends-of-2018.html
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Re: does this master contain clipping?

Postby blinddrew » Sun Dec 23, 2018 7:37 pm

There was a comment in a similar vein in an Inside Track article in SOS a while back (think it was the Lukas Graham, 7 years one) where they talked about deliberately pushing into digital clipping because it was part of the contemporary sound.

[EDIT: here's the article, https://www.soundonsound.com/techniques ... am-7-years it's the chunk at the end but it turns out I may have misremembered]
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Re: does this master contain clipping?

Postby Zukan » Mon Dec 24, 2018 1:41 pm

Did the ME have the original stems?
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Re: Does this master contain clipping?

Postby Guest » Wed Dec 26, 2018 11:17 am

It is not difficult to introduce clipping accidentally. Instead of using eq to attenuate the lower frequencies of electronic textures, I sometimes put a short sample of an unaccompanied female voice into the EQ Match of the Izotope RX7. This invariably introduces clipping if the main track is a reasonably high level. I understand that even cutting frequencies with eq can introduce clipping.
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Re: Does this master contain clipping?

Postby Tim Gillett » Thu Jan 03, 2019 5:31 am

I just came across (again) this talk by Bob Katz and it reminded me of this discussion.

https://youtu.be/xuEi1vLP1SA
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Re: Does this master contain clipping?

Postby Wonks » Thu Jan 03, 2019 11:24 am

Still Vibrations wrote: I understand that even cutting frequencies with eq can introduce clipping.

On some EQs where with very high Q values, the resonance humps around the two cut points are significant enough to raise those frequencies by a few dB. The same goes for the selected frequency point on a very high slope value HP or LP filter.

But that's only an issue if the EQ is put after any limiting and no true peak meter reading is used to check for clipping and levels adjusted accordingly. Put the EQ or filter at a more suitable point in the master bus processing chain and there shouldn't be a problem.

It is however unlikely that such vicious EQing or HP or LP filtering would be needed at the mastering stage. If it was, a good mastering engineer should pass the mix back to the producer to highlight the issue(s) for correction at source, or at least get their go-ahead to make the changes.
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Re: Does this master contain clipping?

Postby Hugh Robjohns » Thu Jan 03, 2019 1:22 pm

Still Vibrations wrote:I understand that even cutting frequencies with eq can introduce clipping.

It can! The wavelength at low frequencies is long, so imagine a situation where you have a low frequency sound element in which its waveform happens to be in its negative-going half-cycle, with simultaneous higher frequency (and loud) sound elements sat on top.

The overall peak level is the combination of the two, obviously, but if you use a high-pass filter to reduce the level of the low note the summation loses much of its negative-going contribution, so the peak level of those higher frequency elements is no longer being reduced and the overall level can appear to rise. Counter-intuitive, perhaps, but a common occurrence nonetheless.

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Re: Does this master contain clipping?

Postby Hugh Robjohns » Thu Jan 03, 2019 2:27 pm

Tim Gillett wrote:I just came across (again) this talk by Bob Katz and it reminded me of this discussion.

Yes, Bob explains the history (and lunacy) of the loudness wars very well, and his descriptions of intentional overload/clipping at the behest of his clients are positively scary!

He talks about 'the trigger points' that lead to the increasing musical compression tactics, and the first was undoubtedly the change Sony made to the metering on their mastering encoders -- which he does mention, but perhaps without the emphasis I think it deserves.

For me, that simple engineering change destroyed the concept of headroom margins, and that opened the doors to poor the audio engineering that lead directly to the loudness wars! Clients could -- for the very first time -- see unused headroom on the metering and that encouraged them to demand its use! :o

Sony PCM1610_1630 Meter compare.jpg


The first mainstream digital encoder designed for CD pre-production, the PCM1610 (on the left above) had a bar-graph meter which was scaled intentionally much like an analogue meter. It had a clear nominal zero reference, and the available headroom margin above was calibrated in positive decibels.

It was specifically designed to look very much like traditional analogue meters, and the only differences were that the headroom region wasn't coloured red -- it should have been! -- and it showed the entire margin all the way up to clipping (unlike any analogue meter) -- which it shouldn't have done!

Ill-judged (in my view) user feedback subsequently encouraged Sony to change the meter design in the new and improved PCM1630 encoder model (right in the image above) to have the meter 'zero' at the very top of the meter, on the grounds that this was the maximum recording level. Big mistake! ;)

Although Sony desperately tried to preserve the notion of a nominal reference level with a headroom margin -- by incorporating an (adjustable) reference marker between the meters -- that concept and facility was largely ignored and was instantly dropped from almost all digital meters thereafter (at least until Bob launched his K-metering system decades later).

It was all such a predictable cockup and a massive shame.... :) Analogue meters evolved the way they did because that arrangement -- a nominal reference level with a vague headroom margin above -- worked brilliantly. By not showing the entire headroom margin the users were encouraged to fear clipping and not abuse it. Dynamics were naturally preserved, reasonably consistent perceived loudness was preserved, and recorded music sounded good.

A system which had evolved over 50 years through good engineering sense was discarded in an instant through an apparently minor design change by a team at Sony... but its knock-ons were massively damaging to the commercial music industry for the next 30 years...

Lunatics and asylums come to mind... :lol:

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