MD: Digital matching a wave (was: If MDs had come out before CDs)
Hi Danny, Danny-K [EMAIL PROTECTED] writes: Let us not forget that digital is in essence trying to achieve a wave that it never can. With due respect (and perhaps I'm misinterpreting what you say), this statement is completely false. Digital achieves a wave perfectly, provided you sample the wave at twice the highest frequency you're trying to capture. Flaws can be introduced in the conversion (A/D and D/A) steps, but these are quantifiable (and appear simply as correlated noise), there's no missing, magic, element of wave-ness that a digital representation lacks. Rick - To stop getting this list send a message containing just the word unsubscribe to [EMAIL PROTECTED]
RE: MD: Digital matching a wave (was: If MDs had come out before CDs)
With due respect (and perhaps I'm misinterpreting what you say), this statement is completely false. Digital achieves a wave perfectly, provided you sample the wave at twice the highest frequency you're trying to capture. Flaws can be introduced in the conversion (A/D and D/A) steps, but these are quantifiable (and appear simply as correlated noise), there's no missing, magic, element of wave-ness that a digital representation lacks. This is what I'm thinking. Think of a perfect sine wave on an old analog oscillator. Digital is in essence a series of ones and zeros. To duplicate that analog sine wave digitally, you are limited to those ones and zeros--up and over. The higher the sampling rate, the smaller those steps--kinda like how you would get jaggies on fonts a few years ago. Monitors have improved so things don't look all pixelesque, just as A/D converters have improved in their resolution. I am curious to learn exactly how sampling at twice the highest frequency changes things. I'm trying to visualize it, but I can't grasp it. - To stop getting this list send a message containing just the word unsubscribe to [EMAIL PROTECTED]
Re: MD: Digital matching a wave (was: If MDs had come out before CDs)
=== = NB: Over 50% of this message is QUOTED, please = = be more selective when quoting text = === From: Danny-K [EMAIL PROTECTED] With due respect (and perhaps I'm misinterpreting what you say), this statement is completely false. Digital achieves a wave perfectly, provided you sample the wave at twice the highest frequency you're trying to capture. Flaws can be introduced in the conversion (A/D and D/A) steps, but these are quantifiable (and appear simply as correlated noise), there's no missing, magic, element of wave-ness that a digital representation lacks. This is what I'm thinking. Think of a perfect sine wave on an old analog oscillator. Digital is in essence a series of ones and zeros. To duplicate that analog sine wave digitally, you are limited to those ones and zeros--up and over. The higher the sampling rate, the smaller those steps--kinda like how you would get jaggies on fonts a few years ago. Monitors have improved so things don't look all pixelesque, just as A/D converters have improved in their resolution. I am curious to learn exactly how sampling at twice the highest frequency changes things. I'm trying to visualize it, but I can't grasp it. Thats one that really got me at first but a quick search using Google has found a document which may be worth reading. Obviouslly there are quite a few technical bits but it does explain something I had real trouble understanding at first-- how you re-create waveforms based on a limited number of samples, and importantly, why oversampling in the D-A stage works. http://www.earlevel.com/Digital%20Audio/Oversampling.html Hope that helps! ___ ___ | || | | o |Gaz Bell - [EMAIL PROTECTED]| o | | || | | o | _ _ | o | | | | __ \ _ _ _ / ___| _ | | | o | | |__| )| __)(_)| _ \| __)| _ \ | | _ ( \|__ / | o | | | | ___/ | / | || | | || | | |_| | | | \ |/ _ | / _/ | | | o | | | | | | || | | || |__ | / | |_| || |_| |/ /__ | o | | | |_| |_| |_||_| |_||)|_) \_/|_||| | | | o || o | | || | | o | ICQ: 36892193 http://www.princegaz.pwp.blueyonder.co.uk | o | | || | | o | An ye harm none, do what ye will | o | |___||___| - To stop getting this list send a message containing just the word unsubscribe to [EMAIL PROTECTED]
Re: MD: Digital matching a wave (was: If MDs had come out before CDs)
* Danny-K [EMAIL PROTECTED] on Wed, 30 May 2001 | I am curious to learn exactly how sampling at twice the highest frequency | changes things. I'm trying to visualize it, but I can't grasp it. Are you familiar with the term jaggies in regards to images displays? Jaggies are the stair-stepping you see when the resolution of the image is lower than the medium. The technical term for this is aliasing. The simplest (but most expensive) anti-aliasing technique is to increase the resolution of the image to the resolution of the medium. This is just as important for printed media as it is for CRTs and LCD panels. The exact same aliasing phenomenon occours in digital audio, and the exact same technique is used to eliminate it: increase the resolution, except in digital audio it is called frequency response (resolution has a partially different meaning). Aliasing occours when the sampling frequency is less than twice the frequency, exactly as you describe. The math is moderately complex, and a physics text book can do a better job of describing it than I can, so I won't :). Anyway, if the higest frequency in a sound is 20kHz, then a sampling frequency of 40kHz will be able to record it with 100% fidelity, assuming you allocate enough bits to store the data. In practice, the top ~25% of the response curve is wasted for roll-off and anti-aliasing filters. So for CD-DA with a sampling frequency of 44.1kHz, the maximum frequency it can sample is 22.01kHz, but the effective high end is ~15kHz. DAT improves on this by increasing the sampling frequency to 48kHz, for a top of 24kHz or an effective frequency response of ~18kHz. And the various DVD-Video and DVD-Audio specs can crank up to a whopping 96kHz sampling frequency, offering frequency response that is indistinguishable from the analog source. -- Rat [EMAIL PROTECTED]\ Caution: Happy Fun Ball may suddenly Minion of Nathan - Nathan says Hi! \ accelerate to dangerous speeds. PGP Key: at a key server near you! \ - To stop getting this list send a message containing just the word unsubscribe to [EMAIL PROTECTED]
