From: rogn@telematikk.idt.unit.no (Egil Rognvik)
Newsgroups: rec.audio.high-end
Subject: Test Report: Does CD Stop Light Work?
Date: 15 Sep 92 13:53:20 GMT
Organization: IDT
Originator: tjk@csd4.csd.uwm.edu

What started this testing was a desire to get some proof whether the "CD Stop 
Light" really worked. I also wanted to know how many interpolations are done.
Because if no interpolations are done then the digital samples presented to 
the DAC are perfect. And if interpolations are done, will the green pen make 
any difference?



How the testing was done:
My CD player is a NAD 5420. It's got the same digital circuits as NAD 5425, 
NAD 5400 and NAD 5000. Also tha DAC is the same. The Digital Signal Processor 
(DSP) is a Sony CXD-1167. It's got the necessary outputs:

pin   signal
19    MUTG
62    C1F1
63    C1F2
64    C2F1
65    C2F2
66    C2FL
67    C2PO

C2FL and C2PO gives the same number of pulses, but I think C2FL is signalled 
when the interpolation is done by the decoder, and C2PO is signalled when 
the interpolated sample is presented to the DAC.

I connected wires to the DSP and buffered the signals before making an 
external connector (quite a delicate matter, as the pin spacing is 0.05 inches 
and the unused pins are not soldered to the PCB, which makes it quite fragile).

The counting of C1F1, C1F2, C2F1 and C2F2 was done using the parallell port of 
a 80486 33 MHz PC (a 12 MHz 286 didn't count fast enough). These signals may 
give 7350 pulses per second (blocks/second).

I made a small program (850 bytes) in assembly. The PC counts for a 
predetermined number of cycles. The cycles are determined by the MUTG signal.
The player does not mute between tracks, but it does mute between preprogrammed
unadjacent tracks. It's also possible that the DSP mutes when multiple 
interpolatios is done, but this never happened. (The program exits with an
audible notification, so I would know if it terminated because of muting 
caused by errors.)

The counting of C2PO was done using a binary ripple counter, as C2PO may give 
88200 pulses per second.



Signal description:
According to "The Compact Disc" by Ken C. Pohlmann the signals mean

C1F1  C1C2
  L     L     No errors detected in C1 decoder
  H     L     1 error corrected in C1
  L     H     2 errors corrected in C1
  H     H     More than 2 errors in C1, data passed to C2
C2F1  C2F2
  L     L     No errors detected in C2 decoder
  H     L     1 error corrected in C2
  L     H     2 errors corrected in C2
  H     H     More than 2 errors in C2 (uncorrectable)

C1F1 and C1F2 high at the same time is hereafter called C1F3, and C2F1 and
C2F2 high at the same time is hereafter called C2F3.

I'm not sure of the correspondence between C2F3 and the number of 
interpolations. It seems, from the counting, that one error in C2F3 gives about
2 to 3 interpolations (one frame contains 12 samples, 6 from each channel).
I guess one error in C2F3 could give up to 12 interpolations.



Some theory:
According to "The Compact Disc" by Ken C. Pohlmann BLER values of 220 per 
second is acceptable. BLER (BLock Error Rate) is the number of blocks 
containing errors (the sum of C1F1, C1F2 and C1F3).
The number of C2F2 permitted is 100 per second, and no interpolations is 
permitted. These numbers are set to avoid audible errors. 
The CD manufacturers may keep within these limits, but you may get one of 
the bad CDs, and dust, damp, fingerprints and scratches will make the CD 
hard to read error-free.

I don't see why the BLER is important, since most of these errors are 
corrected. The only interesting figure should be the number of interpolations.
The number of corrected errors should be inaudible, no matter how many there 
are, but Pohlmann writes that "greater frequency might lead to audible 
faults" (page 250). BLER surely gives information on the quality of the CD, 
but how can corrected errors be audible? Is this caused by digital noise in 
the audible section, a phenomena which will be highly dependent on the design 
of the player? If someone could shed some light on this, i'd appreciate it.



The results:
Notice that the three first tests (Sam Brown test 1, 2 and 3) gives worse 
results than the later tests. This is (and I tested this more thoroughly later)
due to the CD player beeing "cold". The player performed better when it got 
warm. Yet, the differences are small.

I also did repeated countings, but as the results show, the countings give 
very similar results.

The number of interpolations counted is not to be trusted entirely.
Switching a lamp on or off in the same room gave typically a count of 190 to 
220 interpolations. This is also seen in C2F3 and possibly in C2F2, so I 
suspect the player picks up noise from the mains. The power supply is supposed 
to be quite good on the NAD, so this is a bit difficult to understand.

The player does not accept double CDs, so I couldn't test damping discs.

I tested the player's immunity to vibrations by tapping my fingers on the 
player in different directions (not a scientific method, I know). I found that 
the player can take a lot of beating without having problems.

Here's the results (unprocessed data):   (Conclusion at the end.)

Sam Brown "April Moon" tracks 1, 5, 10 and 15. 16 minutes 24 seconds.
1:
Errors in C1F1: 536420
Errors in C1F2:  52671
Errors in C1F3:  62934
Errors in C2F1: 429961
Errors in C2F2:  19469
Errors in C2F3:   1562
Interpolations:   3980
2:
Errors in C1F1: 513693 
Errors in C1F2:  48482
Errors in C1F3:  57630
Errors in C2F1: 397204
Errors in C2F2:  17303
Errors in C2F3:   1475
Interpolations:   3635
3:
Errors in C1F1: 496692 
Errors in C1F2:  46174
Errors in C1F3:  54493
Errors in C2F1: 379214
Errors in C2F2:  15862
Errors in C2F3:   1383
Interpolations:   3263
4:
Errors in C1F1: 485998
Errors in C1F2:  44445
Errors in C1F3:  51186
Errors in C2F1: 355497
Errors in C2F2:  14383
Errors in C2F3:   1201
Interpolations:   2958
5:
Errors in C1F1: 478947
Errors in C1F2:  43165
Errors in C1F3:  50069
Errors in C2F1: 349869
Errors in C2F2:  14070
Errors in C2F3:   1236
Interpolations:   3001
6:
Errors in C1F1: 476672
Errors in C1F2:  42767
Errors in C1F3:  49452
Errors in C2F1: 344348
Errors in C2F2:  14136
Errors in C2F3:   1076
Interpolations:   2479
7:
Errors in C1F1: 475749
Errors in C1F2:  42794
Errors in C1F3:  49750
Errors in C2F1: 344830
Errors in C2F2:  14042
Errors in C2F3:   1175
Interpolations:   2801
8:
Errors in C1F1: 469210
Errors in C1F2:  42205
Errors in C1F3:  49793
Errors in C2F1: 348584
Errors in C2F2:  13732
Errors in C2F3:   1184
Interpolations:   2783
9:
Errors in C1F1: 465379
Errors in C1F2:  41383
Errors in C1F3:  50162
Errors in C2F1: 349398
Errors in C2F2:  14379
Errors in C2F3:   1239
Interpolations:   2924
10: Takes the CD out for some air.
Errors in C1F1: 467278
Errors in C1F2:  42354
Errors in C1F3:  50984
Errors in C2F1: 356219
Errors in C2F2:  13913
Errors in C2F3:   1352
Interpolations:   3149
After treating the CD with "CD Stop Light":
1:
Errors in C1F1: 483089
Errors in C1F2:  44774
Errors in C1F3:  53438
Errors in C2F1: 370455
Errors in C2F2:  15899
Errors in C2F3:   1552
Interpolations:   3860
2:
Errors in C1F1: 485347
Errors in C1F2:  45148
Errors in C1F3:  52343
Errors in C2F1: 361101
Errors in C2F2:  15481
Errors in C2F3:   1322
Interpolations:   3293
3:
Errors in C1F1: 487203
Errors in C1F2:  44931
Errors in C1F3:  52762
Errors in C2F1: 365234
Errors in C2F2:  16302
Errors in C2F3:   1527
Interpolations:   3774
4:
Errors in C1F1: 485566
Errors in C1F2:  45132
Errors in C1F3:  52957
Errors in C2F1: 366534
Errors in C2F2:  15605
Errors in C2F3:   1458
Interpolations:   3629
5:
Errors in C1F1: 489913
Errors in C1F2:  45860
Errors in C1F3:  53568
Errors in C2F1: 370063
Errors in C2F2:  16405
Errors in C2F3:   1849
Interpolations:   4681
Takes the CD out to dry off some dampness.
6:
Errors in C1F1: 481473
Errors in C1F2:  43978
Errors in C1F3:  52209
Errors in C2F1: 361101
Errors in C2F2:  15386
Errors in C2F3:   1648
Interpolations:   4151
7:
Errors in C1F1: 483862
Errors in C1F2:  43473
Errors in C1F3:  52123
Errors in C2F1: 362222
Errors in C2F2:  14905
Errors in C2F3:   1645
Interpolations:   4081
Cleans the CD gently with a dry, clean, soft cloth.
8:
Errors in C1F1: 464517
Errors in C1F2:  39986
Errors in C1F3:  49306
Errors in C2F1: 344543
Errors in C2F2:  13753
Errors in C2F3:   1554
Interpolations:   3868
9:
Errors in C1F1: 467114
Errors in C1F2:  39887
Errors in C1F3:  49446
Errors in C2F1: 344982
Errors in C2F2:  13362
Errors in C2F3:   1650
Interpolations:   4139
10:
Errors in C1F1: 472113
Errors in C1F2:  41254
Errors in C1F3:  49263
Errors in C2F1: 344398
Errors in C2F2:  13477
Errors in C2F3:   1524
Interpolations:   3779

Dire Straits "On Every Street" tracks 1, 3, 7 and 12. 20 minutes 13 seconds.
1:
Errors in C1F1:   8436
Errors in C1F2:    760
Errors in C1F3:   1553
Errors in C2F1:  10473
Errors in C2F2:     20
Errors in C2F3:      0
Interpolations:      0
2:
Errors in C1F1:   8437
Errors in C1F2:    745
Errors in C1F3:   1542
Errors in C2F1:  10676
Errors in C2F2:      3
Errors in C2F3:      0
Interpolations:      0
3:
Errors in C1F1:   8420
Errors in C1F2:    723
Errors in C1F3:   1525
Errors in C2F1:  10272
Errors in C2F2:     17
Errors in C2F3:      0
Interpolations:      0
4:
Errors in C1F1:   8422
Errors in C1F2:    720
Errors in C1F3:   1475
Errors in C2F1:   9972
Errors in C2F2:     25
Errors in C2F3:    103
Interpolations:    206
5:
Errors in C1F1:   8554
Errors in C1F2:    700
Errors in C1F3:   1452
Errors in C2F1:   9423
Errors in C2F2:      9
Errors in C2F3:      0
Interpolations:      0
6:
Errors in C1F1:   8423
Errors in C1F2:    748
Errors in C1F3:   1519
Errors in C2F1:  11066
Errors in C2F2:      7
Errors in C2F3:      0
Interpolations:      0
7:
Errors in C1F1:   8566
Errors in C1F2:    721
Errors in C1F3:   1454
Errors in C2F1:   9682
Errors in C2F2:      6
Errors in C2F3:      0
Interpolations:      0
Takes the CD out for some air:
8:
Errors in C1F1:   8529
Errors in C1F2:    727
Errors in C1F3:   1526
Errors in C2F1:  10289
Errors in C2F2:      9
Errors in C2F3:      0
Interpolations:      0
After treating the CD with "CD Stop Light":
1:
Errors in C1F1:   8621
Errors in C1F2:    760
Errors in C1F3:   1549
Errors in C2F1:  10393
Errors in C2F2:      2
Errors in C2F3:      0
Interpolations:      0
2:
Errors in C1F1:   8638
Errors in C1F2:    708
Errors in C1F3:   1541
Errors in C2F1:  10033
Errors in C2F2:     21
Errors in C2F3:    105
Interpolations:    218
3:
Errors in C1F1:   8687
Errors in C1F2:    713
Errors in C1F3:   1537
Errors in C2F1:  10264
Errors in C2F2:      3
Errors in C2F3:      0
Interpolations:      0
4:
Errors in C1F1:   8664
Errors in C1F2:    766
Errors in C1F3:   1590
Errors in C2F1:  11261
Errors in C2F2:     23
Errors in C2F3:      0
Interpolations:      0

Dire Straits "On Every Street" track 12. 3 minutes 49 seconds.
1:
Errors in C1F1:   2191
Errors in C1F2:    403
Errors in C1F3:    750
Errors in C2F1:   4678
Errors in C2F2:      4
Errors in C2F3:      0
Interpolations:      0
2:
Errors in C1F1:   2218
Errors in C1F2:    406
Errors in C1F3:    753
Errors in C2F1:   4364
Errors in C2F2:      1
Errors in C2F3:      0
Interpolations:      0
3:
Errors in C1F1:   2205
Errors in C1F2:    397
Errors in C1F3:    786
Errors in C2F1:   4643
Errors in C2F2:     18
Errors in C2F3:     98
Interpolations:    181
4:
Errors in C1F1:   2251
Errors in C1F2:    400
Errors in C1F3:    745
Errors in C2F1:   4507
Errors in C2F2:      1
Errors in C2F3:      0
Interpolations:      0
5:
Errors in C1F1:   2173
Errors in C1F2:    412
Errors in C1F3:    752
Errors in C2F1:   4546
Errors in C2F2:      0
Errors in C2F3:      0
Interpolations:      0
After treating the CD with  "CD Stop Light":
1:
Errors in C1F1:   2272
Errors in C1F2:    411
Errors in C1F3:    750
Errors in C2F1:   4502
Errors in C2F2:      3
Errors in C2F3:      0
Interpolations:      0
2:
Errors in C1F1:   2240
Errors in C1F2:    418
Errors in C1F3:    753
Errors in C2F1:   4621
Errors in C2F2:      6
Errors in C2F3:      0
Interpolations:      0
3:
Errors in C1F1:   2243
Errors in C1F2:    414
Errors in C1F3:    754
Errors in C2F1:   4580
Errors in C2F2:      5
Errors in C2F3:      0
Interpolations:      0
4:
Errors in C1F1:   2263
Errors in C1F2:    400
Errors in C1F3:    769
Errors in C2F1:   4718
Errors in C2F2:      3
Errors in C2F3:      0
Interpolations:      0
5:
Errors in C1F1:   2262
Errors in C1F2:    393
Errors in C1F3:    783
Errors in C2F1:   4677
Errors in C2F2:      8
Errors in C2F3:      0
Interpolations:      0

Dance with a stranger "Atmosphere". 38 minutes 36 seconds.
Errors in C1F1:  40918
Errors in C1F2:   2173
Errors in C1F3:   4703
Errors in C2F1:  37263
Errors in C2F2:     52
Errors in C2F3:      0
Interpolations:      0

Classic CD 20 (free with some music magazine). 74 minutes 03 seconds.
Errors in C1F1: 4169275
Errors in C1F2:  931481
Errors in C1F3: 1022126
Errors in C2F1: 5228196
Errors in C2F2:  425229
Errors in C2F3:  246337
Interpolations:  872501

Beethoven-Sonaten played by Daniel Barenboim. 62 minutes 58 seconds.
Errors in C1F1:  181823
Errors in C1F2:   22717
Errors in C1F3:   44999
Errors in C2F1:  334094
Errors in C2F2:    5598
Errors in C2F3:    3180
Interpolations:    6940

Chris Isaak "Wicked Game". 45 minutes 46 seconds.
Errors in C1F1:  20714
Errors in C1F2:   1013
Errors in C1F3:   1717
Errors in C2F1:  14811
Errors in C2F2:      9
Errors in C2F3:      0
Interpolations:      0

Mory Kante "Akwaba Beach". 38 minutes 06 seconds.
Errors in C1F1:  50081
Errors in C1F2:   2258
Errors in C1F3:   3158
Errors in C2F1:  21674
Errors in C2F2:     33
Errors in C2F3:    102
Interpolations:    193



Conclusion:
"CD Stop Light" has no effect on the error rate.
The free CD is of very bad quality.
Most CDs are played error-free (after correction) or with very few errors.



egil

* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *
Egil Rognvik                                * egilro@idt.unit.no
The Norwegian Institute of Technology       * rogn@telematikk.idt.unit.no
Division of Computer Systems and Telematics *
* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *
Newsgroups: rec.audio.high-end