Digital Audio - the signal theory

[DrGeoff]

A great video describing digital audio from a signal theory perspective, and why there are so many myths surrounding sample rate and bit depth, nyquist and dithering.
Not something an Audiophool would want to watch though

[PChi]

Thanks for the link, it's an interesting and well presented video. The explanations and tests do rely on the A/D, D/A, anti aliasing and reconstruction filters all being properly designed. Somthing that can't be relied upon in Audiophool electronics.

[Kalvin]

Thanks for the link, it's an interesting and well presented video. The explanations and tests do rely on the A/D, D/A, anti aliasing and reconstruction filters all being properly designed. Somthing that can't be relied upon in Audiophool electronics.

And the perfect signal will be eventually destroyed by loudspeakers and crossover filters, if not in the amplifier.

[DrGeoff]

Thanks for the link, it's an interesting and well presented video. The explanations and tests do rely on the A/D, D/A, anti aliasing and reconstruction filters all being properly designed. Somthing that can't be relied upon in Audiophool electronics.

And the perfect signal will be eventually destroyed by loudspeakers and crossover filters, if not in the amplifier.

Or, more likely, by the room itself. You can spend as much as you like on all the components, but if the room is not properly designed and treated then the acoustic performance will be rubbish.

[SteveLy]

Thanks for the post. It's good stuff and true. Wish the guy did not disable youtube comments.

Many folk unpappy about audio digitisation don't think of the digitised signals converted back to analog as piecewise continuous steps but as linearly interpolated connect-the-dots signals (just like an oscilloscope displays waveforms in non-interpolated "vector" mode). Hence the belief that well-beyond-Nyquist-sampling will make for a more accurate reproduction because when you make a connect-the-dots plot, the more dots the merrier.

The Nyquist sampling theorem is a mathematically robust one and most audio hobbyists don't appreciate how rock-solid irrefutable it is. But its advocates (including the guy in the video) also underplay the stringency of the underlying assumption that the input signal is bandwidth limited. An old vinyl record may be analog bandwidth limited to ~15 kHz, but the signal vs frequency fall-off is not infinitely steep. There is still signal there well beyond the Nyquist cut-off and that will either be lost (which is usually okay) or more likely, with sloppy AD conversion techniques, show up as aliasing artefacts in the digitised signal.

Digital is as good and better as analog when done right. But sometimes it's not done right.

[kripton2035]

instructive video - thanks.

[EEVblog]

A great video describing digital audio from a signal theory perspective

Damn that's a well produced video.

[DrGeoff]

A great video describing digital audio from a signal theory perspective

Damn that's a well produced video.

Isn't it just. The whole equipment setup is brilliant for demonstration. I particularly liked the shaped dithering demonstration.

[EEVblog]

Isn't it just. The whole equipment setup is brilliant for demonstration. I particularly liked the shaped dithering demonstration.

It would have taken a hell of a lot of time and effort to produce that video.
Small things like the strategically placed walks across camera to simulate a video wipe was a nice touch.
Studio quality lighting, framing, and sound too 
Yes, the interactive dithering demo was superb.

[SteveLy]

The guy is a Red Hat engineer. Not Microsoft Research. And it shows.

[coppice]

Isn't it just. The whole equipment setup is brilliant for demonstration. I particularly liked the shaped dithering demonstration.

It would have taken a hell of a lot of time and effort to produce that video.
Small things like the strategically placed walks across camera to simulate a video wipe was a nice touch.
Studio quality lighting, framing, and sound too 
Yes, the interactive dithering demo was superb.

He has a few other similar quality videos on related topics.

[Delta]

I spotted that video a while back, it really is superb.

It should be compulsory viewing for all audiophools...

[tooki]

I have for years now said that that video is required viewing for anyone who starts talking about digital audio in any way. I really hope he makes more videos.

I am not surprised at all that comments are disabled. Imagine the audiophools coming out to downrate it and post silly comments about how the cables, err, "interconnects", weren't insulated in Rapunzel's hair, etc.

[SteveLy]

Reading the description to the youtube vid, I reckon comments are disabled because the uploader is not the author. Original here: https://www.xiph.org/video/