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This topic comprises 3 pages: 1 2 3
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Author
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Topic: Which system to choose!?
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Gunter Oehme
Film Handler
Posts: 17
From: Frankfurt, Germany
Registered: Jun 2000
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posted 12-17-2000 05:08 PM
Stefan,the problem with the Sony SDDS document is that it is not consistent.
I did not find the defintion of "recording bit rate". 1. Is it the net bit rate of the data stream as you assume?
Each channel would use 333 kBit/s as you calculated.
The compression rate would be 2.4:1 as the data rate of the uncompressed input data is 794 kBit/s.
This is in contradiction to the rate of 5:1 specified by Sony. This compression rate calculates to a bit rate of about 1900 kBit/s for all 12 channels. 2. Is it the physical data rate on the film?
When you look at the figure "Data Block Specification (Release Print)" in the document, you will find the physical parameters given in my post. This calculates to some 2200 kBit/s total recorded on the print.
Is there an additional data reduction I did not see? Dolby Digital: The data rate 320 kBit/s of the AC3 data stream for film was specified by Dolby people. Tom Holman also gives this data rate in various publications e.g. in "5.1 Surround Sound Up and Running".
The common bit pool is no disadvantage to me as it makes best use of the limited bandwith. I agree that the digital format for the A-chain is not everthing.
As John mentioned the acoustics and B-chain is more important for getting good results.
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Stefan Scholz
Expert Film Handler
Posts: 223
From: Schoenberg, Germany
Registered: Sep 1999
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posted 12-18-2000 02:27 PM
Guenter, you are right, it is confusing. I will up the correct data, and post later here. I have taken my information from the 1994 edition of the recorder manual, and you're right 44.1 k samples @ 18 bit is about 795k linear PCM. This would relate to a compression rate of 2.5, and officially it's 4.5 : 1 (unrounded).
Interesting, and results to follow.One test, which someone might conduct. Play Pink Noise in all formats over a good B chain (please, no 2 way systems in 450 seat theatres), correctly designed.
And I would be curious about the results.
Which Pink Noise signal sounds best, comparison: Standard PN generator from tech kit.
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