lakshmant

A question about decoder IC 's of dolby and DTS

what exactly is meant by a group A dolby decoder and yamaha claims their decoder is a dolby group A decoder then i have a onkyo dvs 757 THX player with a crystal chip does it not meet dolby's highest standards as it is not advertised a group A decoder as it is integrated video +audio deocoder

can anybody who has a good knowledge of chips DSP etc explain this and what is the diffrence between MOPS and MIPS
in the DSP world and how many mops equals a MIP

Roger Dressler

The Group A designation was once used for internal communication between Dolby and its licensees regarding certain specs the decoder chip had to meet. It was not intended for advertising copy, and has since been retired.

Roger Dressler

lakshmant

thank you so much for your reply and i love your articles on PLogic on the dolby website read them many times
but is there any basic difference in the chips which various firms like zoran ,cirus, analog devices etc make or is the decoding in them exactly the same if so why do companies choose one chip over the other is it for features or for quality of the chip and its speed i:e faster the chip better the decoding quality.

Also could i know what the CP650 IC make is it is such a great processor so much better sonically and feature wise compared to the cp500 which i love very much.

Roger Dressler

>>is there any basic difference in the chips which various firms like zoran ,cirus, analog devices etc make or is the decoding in them exactly the same if so why do companies choose one chip over the other<<

There can be differences in the code design, or the optimization of the decoder algorithm in various chips. But all have to successfully decode the hundreds of Dolby Digital test vectors. If they didn't, then rather than merely sounding different, the decoders could malfunction. There was once a DSP company making a strong claim that their 24-bit device sounded better than another using 20-bit architecture. But no measurable test we performed revealed any difference.

But there are many differences among the DSPs that make them attractive to different product makers, such as ease of customizing the code, embedded features (like S/PDIF receivers), internal vs external RAM, cost, familiarity, availability, etc.

>>Also could i know what the CP650 IC make is it is such a great processor so much better sonically and feature wise compared to the cp500 which i love very much.<<

I don't know what's in the CP500, but I think the CP650 uses Motorola DSPs. 12 of them, to be exact! But the sound quality difference is probably due to much better DACs and analog circuit design rather than the DSP.

Roger Dressler

BrianWoerndle

MOPS = Millions of Operations per Second.
MIPS = Millions of Instructions per Second.

An Operation is a complete unit of work, and can contian any number of instructions.

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