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Method for Synchronizing a Compact Disk ROM Drive Transmitting CD Digital Audio Information Through an SCSI Bus to a Host System Digital Signal Processor

IP.com Disclosure Number: IPCOM000106905D
Original Publication Date: 1992-Jan-01
Included in the Prior Art Database: 2005-Mar-21
Document File: 2 page(s) / 74K

Publishing Venue

IBM

Related People

Kerins, TM: AUTHOR [+2]

Abstract

This article describes a method for preventing data buffer overruns or underruns when a digital signal processor (DSP) is playing compact disk-digital audio (CD-DA) data transmitted by a CD-ROM drive through a small computer system interface (SCSI) bus.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 52% of the total text.

Method for Synchronizing a Compact Disk ROM Drive Transmitting CD Digital Audio Information Through an SCSI Bus to a Host System Digital Signal Processor

       This article describes a method for preventing data
buffer overruns or underruns when a digital signal processor (DSP) is
playing compact disk-digital audio (CD-DA) data transmitted by a
CD-ROM drive through a small computer system interface (SCSI) bus.

      When a DSP is playing CD-DA audio data received from a CD-ROM
drive through the SCSI bus, there is a potential problem with audio
buffer overruns or underruns between the CD-ROM drive and the DSP.
This is due to the fact that there is no way to synchronize the clock
of the DSP with the clock of the CD-ROM drive.  While the CD-ROM
drive is filling the audio buffer with audio data at one data rate,
the DSP is emptying the audio buffer at a slightly different rate.
Because of this speed difference, eventually one of two conditions
will occur:
1.   If the DSP is running slightly faster than the CD-ROM drive, the
DSP will pull data from the audio buffer faster than the CD-ROM drive
can fill it.  This will eventually result in a buffer underrun
condition where the DSP will try to read data from an empty buffer.
2.   If the CD-ROM drive is running slightly faster than the DSP, the
CD-ROM will put data into the audio buffer faster than the DSP can
empty it.  This will eventually result in buffer overrun condition,
where the CD-ROM will try to write data to a full buffer.

      The technique described in this article to solve this problem
is to servo the CD-ROM data rate to the DSP data rate.  Since the
CD-ROM clock cannot be connected directly to the DSP clock due to the
fact that the CD-ROM drive is connected through the SCSI bus to the
...