dean Wrote:
> I'm not entirely sure I understand the problem well enough to say
> that this patch is correct.
>
> (I realize that there has been some listening tests done and you like
>
> it better, but I want to also make sure it's correct.)
>
> Given that the Squeezebox has a 24 bit output, the rounding error
> should be down at around at 138-144dB, not 90-96dB and I have a hard
> time believing that the effect would be as obvious as you state at
> that level.
I am not sure how audible the difference is, but in my opinion it is
"cleaner" to multiply with gain coefficients that does not lead to bits
being lost because of rounding.
I suggest to modify the gain coefficients for volume settings from
-30dB to 0dB so that the patch becomes:
Index: server/Slim/Player/Squeezebox2.pm
===================================================================
--- server/Slim/Player/Squeezebox2.pm (revision 5190)
+++ server/Slim/Player/Squeezebox2.pm (working copy)
@@ -272,7 +272,12 @@
# Map a floating point dB value to a 16.16 fixed point value
to
# send as a new style volume to SB2 (FW 22+).
my $floatmult = 10 ** ($db/20);
- return int(($floatmult * (1 << 16)) + 0.5);
+ if ($db >= -30 && $db <= 0) {
+ return int($floatmult * (1 << 8) + 0.5) * (1 << 8);
+ }
+ else {
+ return int(($floatmult * (1 << 16)) + 0.5);
+ }
}
sub volume {
With this patch the differences between "trunk" gain and "patch" gain
are listed below.
The differences are small, but again, I think the patch gain
coefficients are "cleaner".
In my opinion, it can't hurt to use the patch gain.
The purists will be satisfied if it is applied...
Steinar
dB Trunk Patch
0 65536 65536
-1 58409 58368
-2 52057 51968
-3 46396 46336
-4 41350 41472
-5 36854 36864
-6 32846 32768
-7 29274 29184
-8 26090 26112
-9 23253 23296
-10 20724 20736
-11 18471 18432
-12 16462 16384
-13 14672 14592
-14 13076 13056
-15 11654 11776
-16 10387 10496
-17 9257 9216
-18 8250 8192
-19 7353 7424
-20 6554 6656
-21 5841 5888
-22 5206 5120
-23 4640 4608
-24 4135 4096
-25 3685 3584
-26 3285 3328
-27 2927 2816
-28 2609 2560
-29 2325 2304
-30 2072 2048
-31 1847 1847
-32 1646 1646
-33 1467 1467
-34 1308 1308
-35 1165 1165
-36 1039 1039
-37 926 926
-38 825 825
-39 735 735
-40 655 655
-41 584 584
-42 521 521
-43 464 464
-44 414 414
-45 369 369
-46 328 328
-47 293 293
-48 261 261
-49 233 233
-50 207 207
--
sbjaerum
------------------------------------------------------------------------
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View this thread: http://forums.slimdevices.com/showthread.php?t=17269
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