Xiph's Episode 2: _Digital Show & Tell_ is out, Second digital media geekout video from Xiph.Org Options

[xiphmont]

Xiph Episode 2: Digital Show & Tell is out!

"The second video from Xiph.Org explores multiple facets of digital audio signals and how they really behave in the real world. Sampling, quantization, dither, band-limiting, and vintage bench equipment all in one video!"

It's a followup in a sense to the 24/192 article of last year. Other videos: http://xiph.org/video/

This post has been edited by greynol: Feb 27 2013, 17:43

Reason for edit: Removed the "!" from the title per news submission guidelines

[bennetng]

Interesting to see the "not stairstep" illustrations. I was a sound engineer in toy design field and needed to compose/arrange music, sound effects and record voice dialogs for several kinds of low-end MCUs. Our customers often complained the sound quality (they don't know what is aliasing, they described the distortion as "metallic noise") but we just explained to them that the speakers (usually about 25 to 40mm diameter) were to blame. We won't tell them the truth.

I generated a sine sweep and digitized the analog output of those MCUs and found that the waveform is even worse than zero order hold, it looks like sawtooth.

[_if]

Monty, that was a great video. I thoroughly enjoyed it and I really would like to see more. Normally watching all of a 20-minute Internet video feels like a chore to me, but this was really good and even my not-really-techie girlfriend liked it. You should make these more often.

Interesting to see the "not stairstep" illustrations. I was a sound engineer in toy design field and needed to compose/arrange music, sound effects and record voice dialogs for several kinds of low-end MCUs...

Sorry for the off-topic, but this is interesting to me to finally hear. I've long suspected the speakers were not really the primary reason children's toys sound so terrible, since it sounded more like very low quality digital and, weirdly enough, I'd like to hear more about the mechanics of it. It seems the sound quality hasn't gotten much better since the '90s and I've wondered why when you'd think it wouldn't be prohibitively expensive to put a decent chip in.

[bennetng]

I'd like to hear more about the mechanics of it. It seems the sound quality hasn't gotten much better since the '90s and I've wondered why when you'd think it wouldn't be prohibitively expensive to put a decent chip in.

OK I can reveal more facts as I am not working in the toy field anymore and it is not totally off-topic. Those chips use some sorts of DPCM formats and their compression efficiency is extremely low. In order to save space we need to use multiple sample rates manually to store audio data. For example when storing the phrase "It is an apple", consonants with more high frequencies like "t" and "s" are stored in 12khz and other parts are in 8khz. When saying "It is an orange", "It is an" will be reused. When there are any silence parts more than 200ms between the phrases we need to measure then delete the silences in the wave files to save space and manually add the silences back in the MCU's IDE with some sorts of scripting languages. As you can see, I was doing what a modern lossy audio codec can do MANUALLY.

The toy field is affected by the loudness war as well. Because louder sound components are more expensive and need more battery power, we are required to compress and hard-limit the sounds to insane level, of course it will introduce more artifacts but yes, the speakers were to blame. We can also say the cabinet of the product is not acoustic-friendly (train-shaped, hamster-shaped...) therefore they produced odd-sounding harmonics...

[_if]

... As you can see, I was doing what a modern lossy audio codec can do MANUALLY...

Thanks for that info. I was right, it is interesting! Manual lossy compression work and loudness wars in children's toys, I did not expect to hear that. Is it wrong to think an extra few pennies invested in hardware could have saved you quite a lot of work and ended the customer complaints? I suppose I don't actually know how much more storage would have cost, but it seems like just a little bit more would have gone a long way.