Xiph Episode 2: Digital Show & Tell

An anonymous reader writes "Continuing a firehose tradition of maximum information density, Xiph.Org's second video on digital media explores multiple facets of digital audio signals and how they really behave in the real world. Demonstrations of sampling, quantization, bit-depth, and dither explore digital audio behavior on real audio equipment using both modern digital analysis and vintage analog bench equipment... just in case we can't trust those newfangled digital gizmos. You can also download the source code for each demo and try it all for yourself!" Plus you get to look at Monty's beard and hear his soothing voice. There's a handy wiki page with further information and a summary of the video if text is your thing.

Comments

I jus happened to have watched part 1 last week

[Mister Liberty]

Found it very informative to a non-guru.

Aside from that, the video and its audio, and I'm not kidding here,
were very pleasant and sympathetic to the ears and eyes.

Re:soothing? verarschst Du?

[cheater512]

If a 100Mhz analog scope can't detect the stair steps, then there is absolutely no fucking way you have the slightest chance of detecting it.

100,000,000 Hz vs your ears at maybe 20,000 Hz.
See the difference?

Re:soothing? verarschst Du?

[Anonymous Coward]

He has actual hardware there, as he explains quite old consumer grade hardware, which does the conversion from analog to digital to analog, and the result is still for all intents and purposes PERFECT. Yes, the delivery is smug, but rightly so. Talking to "audiophiles" is like talking to people who believe in homeopathy: It is extremely difficult to not just make fun of the fools. When you instead manage to deliver an explanation and a demo that clear, you get to be smug. (Captcha: mockery)

Re:soothing? verarschst Du?

[Aguazul2]

He knows what he is talking about, he explains things clearly, he is not condescending to the viewer -- I think the apparent smugness is not for real, or maybe it is just how his personality comes over. And if you still don't understand how there is no stair-step, you need to watch the video again! Even though I've done loads of DSP, the nice demos he gives really illustrate well what he is saying, and who can argue with pure-analogue gear proving the point -- not just theory and hand waving, but real experimental evidence. Really nice work.

Re:soothing? verarschst Du?

[frank_adrian314159]

See the difference?

But, but, but... I'm an audiophile, dammit! I listen with my soul. That's why I can hear it!

This is good

[ceoyoyo]

This guy knows what he's talking about, and communicates it well. Amateur audiophiles should especially read his article here: http://people.xiph.org/~xiphmont/demo/neil-young.html.

full props to Monty

[nadaou]

... for all the bullshit Blackboard technology mess, videotaped classroom lectures, and .edu buzzwords, this sort of thing is exactly how open education should be done.

congrats Monty, once again you've done well.

Re:soothing? verarschst Du?

[Anonymous Coward]

Never underestimate the power of self-delusion. Placebo effects have been accepted by science as being very real. The fact that someone, whether a believer in homeopathy, audiophile-quality, sugar pills or whatever scientifically-unsubstantiated nutjobery, actually believes in it is beneficial to them. Trying to take away their self-delusions is just plain mean. I really wish I could convince myself that what amounts to water is as effective as real medicine...I might be a healthier person.

Re:Using real world audio waveforms?

[jmv]

Could you please post the specs of the reel to real equipment you're using. To beat a 16-bit digital system, it has to have better than 96 dB SNR and dynamic range. I don't remember having ever seen that.

Re:Using real world audio waveforms?

[ceoyoyo]

He says several times that he used sine waves as a simple illustration. Then he switches to square waves. You apparently don't understand sampling theory well enough to understand why your second sentence, in the context of PCM audio, is incorrect. Perhaps reading this will help: http://people.xiph.org/~xiphmont/demo/neil-young.html.

On the other hand, you might just be an AC troll, an "audiophile" or an old enthusiast or sound engineer who might have been an excellent technician but never developed a proper understanding of signals. In any case, anybody tempted to agree with your post should read the article at that link.

Great lesson, but what's with the audio?

[wonkey_monkey]

For a video all about audio, why does the guy's voice keep flapping around from left speaker to right speaker? I found it pretty distracting. Next time, try a clip-on mic and mix it down to mono unless it's necessary to make a point.

Re:Great lesson, but what's with the audio?

[xiphmont8352]

I intentionally avoid using lavalier mics. Their amplitude and timbre are all over the place depending on the direction you're looking, they pick up clothing noise, and you're either tethered to a wire or have to deal with the complexity and limitations of a wireless system.

Headsets work better overall, but are highly visible and still add a layer of complexity. They also sound like someone talking directly into your ear. Even with additional postprod [going all the way to room modeling], I've never managed to make a headset sound totally natural. If others have, I'd appreciate some tips.

In any case, as someone who spent ten years dealing with lavs and headsets in live performance as a sound engineer, I avoid them in my own time as much as humanly possible :-)

The stereo image was intentional, it's a trick for removing perceived echo/reverb by spreading it out across a stereo image instead of it all piling up right behind the voice in mono. That said, the image was wider than I'd have liked. That was a result of mic placement and angle, another tradeoff to avoid wide amplitude changes as I moved around.

FWIW, several other video producers wrote me to ask how I got such great sound without a lav, and (like you) others wrote to mention that they found the very wide stereo distracting. I'll tinker with it more in the next vid.

Re:Using real world audio waveforms?

[iluvcapra]

While Monty's presentation is excellent, what we have to remember is we are not listening to pure sine waves.

We listen to nothing more than sums of pure sine waves.

Re:soothing? verarschst Du?

[wiredlogic]

SACDs are encoded with a 1-bit sigma-delta pulses. Those would be some pretty whopping staircases if sampling theory didn't work to eliminate them.