dpuchals@demos.intel.com (Douglas R. Puchalski) (06/26/91)
I have a few questions relating to digital audio and standard audio casettes. 1) Does anybody know how to read raw audio data from a CD in a CD-ROM player on a rs6000 or a dec3100 so that the audio waveform(s) can be analyzed? 2) What are the current schemes being thought of for audio data compression? I've heard about using a displacement from the previous value pretty recently. I'm talking about NOT compromizing a 16bit digital signal in any way, as the mini-CD format does do, I believe. 3) What is the bandwidth (per square inch/cm) of standard audio tape? (or would it be cross section in inches??) Thanks, Doug Puchalski
gt8021a@prism.gatech.EDU (EASON) (06/27/91)
In article <4870@inews.intel.com> dpuchals@demos.intel.com (Douglas R. Puchalski) writes: >I have a few questions relating to digital audio and standard >audio casettes. >1) Does anybody know how to read raw audio data from a CD in a > CD-ROM player on a rs6000 or a dec3100 so that the audio > waveform(s) can be analyzed? I've been working with Hitachi CD-ROM drives for close to a year now, writing a driver and higher software. Every ROM or audio block on a CD has, associated with the data, a subcode which tells the type of data in the block, and whether or not a digital copy of the data is allowed. Every audio CD I have looked at has the "no copy bit" set to 0 (no copy allowed), and the drive returns an error status when a request is made to read those blocks. You can give the drive an audio play command (built-in D/A converter & headphone jack), and everything plays fine, but you can't get a digital copy of the audio. This may be a Hitachi-specific hardware copy protection implementation, but it would not surprise me at all if (most/all) other CD-ROM manufacturers had this, too. Rather disappointing to a DSP student! Anyone know the RS-6000 in particular? Who makes their drives? BTW, we have one in our lab here, so I could check later if no one else knows. -- Bill Eason - EE (DSP) grad student Georgia Institute of Technology, Atlanta Georgia, 30332 uucp: ...!{decvax,hplabs,ncar,purdue,rutgers}!gatech!prism!gt8021a Internet: gt8021a@prism.gatech.edu
grahaf@otago.ac.nz (06/27/91)
In article <31848@hydra.gatech.EDU>, gt8021a@prism.gatech.EDU (EASON) writes: > In article <4870@inews.intel.com> dpuchals@demos.intel.com (Douglas R. Puchalski) writes: >>I have a few questions relating to digital audio and standard >>audio casettes. >>1) Does anybody know how to read raw audio data from a CD in a >> CD-ROM player on a rs6000 or a dec3100 so that the audio >> waveform(s) can be analyzed? > > I've been working with Hitachi CD-ROM drives for close to a year now, > writing a driver and higher software. Every ROM or audio block on a CD > has, associated with the data, a subcode which tells the type of data > in the block, and whether or not a digital copy of the data is allowed. > Every audio CD I have looked at has the "no copy bit" set to 0 (no copy > allowed), and the drive returns an error status when a request is made > to read those blocks. You can give the drive an audio play command > (built-in D/A converter & headphone jack), and everything plays fine, > but you can't get a digital copy of the audio. > Very curious. I have seen a number of high end audio CD players with Digital Out connectors on the back. I have seen them playing CDs through an amp which has the appropriate hardware without any audio leads. The sugestion is that the Digital Out is raw data and the amp does the A/D conversion. I have no idea if this is what actually happens but there is only one cable to the amp from the player. The connectors are just phono plugs and the cable is standard audio. It may be possible to get the data this way. Not as fast or convienient as a CD-ROM but.... Good luck, Graham.
charlesg@nntp-server.caltech.edu (Charles Grosjean) (06/27/91)
You can use a Yamaha YM3623B to take a standard digital out from a CD or DAT player and then get digital out along with sucode out. The chip also has outs for copy disabled/enabled, and the category (DAT) or other than DAT. This is a very common chip (in digital audio) that is used in the D/A section of many cd players. If the CD-ROM drives had a chip like this in it, you could patch the output that list copy/no copy, otherwise you could take the raw data from the digital out and process it yourself. Yamaha's address is: YAMAHA Systems Technology 981 Ridder Park Drive San Jose, CA 95131 408/437-3133 FAX: 408/437-8791. They don't give samples, but the chip can be obtained through Marshall. Disclaimer: I'm just a satisfied user.