From mboxrd@z Thu Jan 1 00:00:00 1970 From: David Olofson Date: Sun, 24 Oct 1999 17:42:18 +0000 Subject: Re: streaming from disk to terminatorX added (via mmap) Message-Id: List-Id: References: In-Reply-To: MIME-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable To: linux-sound@vger.kernel.org On Sun, 24 Oct 1999, Benno Senoner wrote: > PS: Now if we could get one of these turntables recorded with special > static waves (saw waves), we could add add turntable motion detection > and get the same features as "finalscratch" on BeOS: > scratching an audiofile in realtime using a real turntable. > :-) Uhm, I have just developed a sensor decoding method that could be useful for this. It's probably overkill, as it's accurate to some 128 bits/period of the input signal with input signals of around that resolution. It's just that I most probably can't release the details... :-( Anyway, I have a clue about how to do it, so I could give some hints if needed. And there are other ways than a special LP. For example, a quadrature decoder; get two reflective optisensors (UV LED + photodiode in a single package - handy! :-), and use an encoder stripe around the turntable disk. The encoder strip should look like this: Sensor 1: #### #### #### #### #### Sensor 2: #### #### #### #### #### Note: 90 degree phase diff! Then run the "sensor 1" signal into the U/_D input of a binary counter. (Standard chip - use 4xxx chips [CMOS], as they're less sensitive to Vcc errors. Do *not* use buffered chips as triggers for reading the sensors - they can start to oscillate and fry!) The "sensor 2" signal goes to the count input of the chip. The chip is then hooked up to a parallel port or something, so that you can read the current value. Of course, you may also rip out the electronics from a mouse. (Preferably a PS/2 one, as they have 30-150 Hz update rate, as opposed to 10-30 for serial mice...) That's two channels and some buttons + decoder and interface - and there are drivers. :-) Remove the LEDs and photodiodes/transistors from the mouse PCB, and replace them with wires to the new detectors. //David =B7A=B7U=B7D=B7I=B7A=B7L=B7I=B7T=B7Y=B7 P r o f e s s i o n a l L i n = u x A u d i o - - ------------------------------------------------------------- - - =B7Rock Solid David Olofson: =B7Low Latency www.angelfire.com/or/audiality =B7Audio Hacker =B7Plug-Ins audiality@swipnet.se =B7Linux Advocate =B7Open Source =B7Singer/Composer