What does this limit in the blue waves mean? (clipping)

Audacity Help Forum Windows
1

Hi,

I got two different rips of a song, one in mp3 and another in FLAC. I assume the FLAC version is better than the mp3, but I don’t know the source of any of them, so this assumption could be wrong. When I added both of them to Audacity and compared them, I noticed some things I don’t exactly understand, hope you guys can help me with this load of questions :mrgreen: .

HD: http://fotos.subefotos.com/fd180c0b3db4ee966ecaece11fde4367o.png

I’ve ripped a lot of CD’s and never ever had that straight limit. But it’s a FLAC, so that kind of tell me it should be better. :question:

  1. The limit of the blue wave (circled green).
    a) Why is it straight?
    b) What does it mean?
    c) Should I trust in an audio source that has those straight parts in the audio waveform?

  2. Clipping lines.
    a) Are they always bad?
    b) Not a single one of my CD rips has those red lines indicating clipping. Nevertheless, I don’t notice any distortion at all when listening to those tracks.

HD: http://fotos.subefotos.com/59fb255b099ea64e2d84c61572c7930co.png

  1. Smoothness of curves and dots.
    a) What means each different dot? A sample is what’s between 2 dots?
    b) A smoother curve, what means? Better resolution? (circled in red)
    c) Can I use those curves to identify what is the highest audio quality track?
    d) A 24 bit audio has more dots (smoother curves, more resolution) than a 16 bit audio?

Thank you very much! :ugeek:

2

You don’t know. FLAC can be a very good reduced-bit uncompressed sound file system, but if the show was made from an original MP3, you may just have two MP3 damaged sound files, one with really high quality damage.

It’s almost a sure bet that if you got them via download, they were MP3 at some point. Nobody transfers WAV or other uncompressed files unless for critical production not for public consumption.

You’re right, flat-top portions of a performance are unnatural. Nobody can play a violin like that. Also, overall blue waves that seem to hang at one level for a long time are also unnatural. That points to great processing and post production.

The flat portions, unless you know where they came from are sound damage. You can get that by intentionally clipping the blue waves or trying to tap-dance your way out of sound damage by reducing the volume of an already damaged performance. That just gives you quieter damage. But it does drag you out of range of the Audacity clipping indicators, so there is that. It’s still clipping, but Audacity can’t find it.

Overload/clipping happens when the sound gets so loud that the digital system runs out of numbers. The digital system stops giving a faithful representation of the original show. You can’t, as a rule, recover any clipped work in post production.

Number 2.

The Four Horsemen of Audio Recording (reliable, time-tested ways to kill your show)
– 1. Echoes and room reverberation (Don’t record the show in your mum’s kitchen.)
– 2. Overload and Clipping (Sound that’s recorded too loud is permanently trashed.)
– 3. Compression Damage (Never do production in MP3.)
– 4. Background Sound (Don’t leave the TV on in the next room.)


Koz

3

Thanks you very much, Koz. What about the questions of the number 3? (last image)

4
  1. Clipping lines.

Red clipping lines are good for a week long discussion, or more.

Clipping like I said is when the system runs out of numbers and can’t get any louder. So you can’t ever know whether the music intended to get louder or not. All you can do is guess at it. The old clipping indicator took any blue wave at 0dB and called it clipping. That resulted in millions of false positives because a lot of modern music (EDM for one example) is heavily processed to live at 0 without going over. The time line turns into a bright red block and that’s correct and expected behavior.

So then you get into the weeds of what does the blue wave look like when it intends to go over? If you have two samples at 0 is that enough? Three? By three samples you almost certainly have clipping damage and missing data, no musical instrument can do that, but you may have that with two samples at 0…

And etc. We sent out for coffee multiple times and I think the resolution was two different clipping tools. The obvious one on the timeline is early-warning and Analyze > Find Clipping is the final word.

  1. Smoothness of curves and dots.

You first need to know that the blue waves only show you the loudest 30 dB or so of the show. It’s in percent, not dB. Sound goes double and half every 6dB. So at 12% blue wave, you’re only down 24dB out of 60dB audible range.

That’s the important range and it’s relatively easy to find edit points by doing that. You can see the entire musical range with the left-hand drop-down menu > Waveform dB. I have trouble editing with those waves, but they do show you everything.

The sideways spacing between the wave points is sample rate (44100) and the vertical spacing is bit depth (16-bit, 24-bit, 32-bit, 32 Floating).

44100, 16-bit Stereo is used in Audio CDs.
48000, 16-bit Stereo is used in Digital Television.

So they’re not toys.

The advanced formats like 96000, 24-bit, Stereo are used in Studio Music Production. They don’t sound any better, but they let you plow through more special effects, filters an post production before the show sound gets ratty.

My digital spidey sense is telling me you’re going to start worrying about your sound at the bit level like a good scientist. We don’t do scientists well. Audacity is a music production editor, not a WAV editor. If there’s a decision to be made whether to make the bits surgically accurate or sound good, we’ll go with sound good.

For one example, when a high quality WAV file is exported, a very tiny amount of noise (dithering) is added to keep internal bit depth resampling errors from ever lining up and becoming audible. This drives the scientist nuts.

“I put three bits in there and only two came out!!!”

Koz

5

Lol, you’re funny explaining stuff :mrgreen:

Thank you, and don’t call me scientific of sound or something like that, I’m the noobest user here in the sound topic. I’m just curious when I see certain things, and ask the experts :nerd:

Have a nice day!