Every type of digital audio signals has a unique pattern (Dolby Digital AC-3, Dolby Digital EX, DTS, DTS-ES Matrix 6.1, DTS-ES Discrete 6.1, DTS 96/24, HDCD, MPEG-1, Layer III, MPEG Multichannel, Linear PCM, and yes even digital silence (all 1's or all 0's).
With this in mind, the DSP is responsible for reporting to the host microcontroller (Toshiba 100-pin part located on the main board) what "pattern" it currently is seeing.
If it sees AC-3 (Dolby Digital), then it tells the host controller, "I have autodetected a Dolby Digital signal, please load the Dolby Digital code (or Dolby Digital EX code or Dolby Digital 2/0 + Pro Logic II code or Dolby Digital + Cirrus Extra Surround code) - depending on what processing mode the listener prefers"...the controller does just this.
So, imagine if you will that a Linear PCM stream contained a small segment of data that "looked" identical to that of AC-3, DTS or some other type of compressed data or digital silence...
The DSP would originally report that it was processing Linear PCM data...but then, all of a sudden, the stream emulates that of a compressed stream...so the DSP reports that the stream type has changed to the host controller and automatically mutes the outputs... the host controller, then starts to load the proper DSP code to decode this new type of stream... but just as it is finished, the DSP then reports to the host... now the stream is Linear PCM again... please load the preferred PCM processing code... this would sound to the listener as a "drop in audio" or a brief muting of sound, when there should not have been one.
The "initial" signal lock time, has more to do with the S/PDIF receiver. The 950 uses the world-standard Cirrus Logic "Crystal-brand" CS8415A, so lock time for almost any bi-phase mark encoded signal (regardless of the physical connection being optical or coaxial) should be around .5 to 2 seconds, depending on the quality of the biphase mark encoded signal being transmitted from the source, and the sampling frequency.
Keep in mind that a S/PDIF receiver only converts biphase mark encoded data to I2S digital audio format, which is fed to the DSP. If the S/PDIF transmitter in the source device (CD player, DVD player, STB, DAT machine, etc.) stops sending a valid biphase mark encoded signal (which can happen during a track change or station change or FF or RW, depending on the manufacturer)
The DSP inside the 950 is a Cirrus Logic "Crystal-brand" CS49326 (www.cirrus.com
) which is a dual-engine 24-bit, fixed-point Audio DSP. It is the worlds most commonly used Audio DSP in most of the AVRs and Processors.
Try disabling the "autodetect" feature and select PCM only for these "troublesome" CDs see if an audio dropout still occurs... surely there was some reason why this ability is included in the 950.
The Oracle has spoken...
[This message has been edited by Scott (edited February 05, 2003).]