Rockbox

  • Status Closed
  • Percent Complete
    100%
  • Task Type Patches
  • Category Music playback
  • Assigned To No-one
  • Operating System All players
  • Severity Low
  • Priority Very Low
  • Reported Version Release 3.6
  • Due in Version Undecided
  • Due Date Undecided
  • Votes
  • Private
Attached to Project: Rockbox
Opened by Bertrik Sikken - 2010-11-21
Last edited by Michael Sevakis - 2012-05-01

FS#11767 - Meier crossfeed

Attached patch adds a new crossfeed algorithm to rockbox, emulating the basic “Meier” crossfeed (2 capacitors, 3 resistors) as discussed in http://www.meier-audio.homepage.t-online.de/passivefilter.htm

This crossfeed blends a bit of low-pass filtered L signal into the R signal (and vice versa) while adding about 300 us delay to the crossfed-signal. A difference with the crossfeed already present in rockbox, is that this algorithm keeps the total spectrum flat (the one currently in rockbox accentuates low-frequency signals, making it sound a bit muffled).
This implementation is quite lightweight, just 3 multiplies per left-right pair of samples, but only has a C implementation right now (no asm).

The crossfeed effect is quite subtle and is noticeable mostly one albums that have very strong left-right separation (e.g. one instrument only on the left, another only on the right).

In the user interface, the new crossfeed option appears as “Meier” and is not configureable. The existing crossfeed is renamed to “Custom” as it allows itself to be customised.
There is no entry for the user manual yet.

Closed by  Michael Sevakis
2012-05-01 08:27
Reason for closing:  Out of Date
Additional comments about closing:  

Synced to 0dd00b33 and moved to gerrit.
http://gerrit.rockbox.org/r/#/c/227 /

sideral commented on 2010-11-27 23:34

Nice addition. I tested this patch on a few files, and I do indeed have the impression that it accomplishes its objective (crossfeed) without requiring configuration and while maintaining a better sound quality.

Martin Sägmüller commented on 2010-12-14 13:44

I tested this v3 patch with some “regular” and some very hard-panned music. It’s really rather subtle, and IMO the v2 of this patch had more beneficial effects while still maintaining good audio clarity. Would it be possible to keep the v2 version next to this v3 one, for example selectable as “Meier 1” and “Meier 2” in the menu?

sideral commented on 2011-03-04 17:51

I haven’t seen a v2 version of this patch anywhere. Does anyone of you still have that version lying around somewhere, and if so, could you please post it here?

In my view, the current Meier-crossfeed feature (v3 patch) is superior to Rockbox’s standard crossfeed feature (better sound quality, no configuration needed) and could actually replace it. I find it hard to imagine anyone actually fiddling with the plethora of crossfeed settings we have today.

Martin Sägmüller commented on 2011-03-04 18:58

V2 is the last post in  FS#11577 .

The only difference between v2 and v3 are two digits. In dsp.c replace both (0x7fffffff/NATIVE_FREQUENCY) with (0xffffffff/NATIVE_FREQUENCY).

Mark commented on 2011-05-14 19:57

Can we go ahead and get this added into the releases? I’ve been using it for months on my Clip+ with dfkt’s build, and it’s rock solid. I’d really like to get this on my 5.5G iPod too.

Johnny Chang commented on 2011-06-15 15:29

Does this implement the frequency dependent delay to counter the comb effect?

Bertrik Sikken commented on 2011-06-15 19:02

Eruditass, this implementation should have no comb effect.

mysiak commented on 2012-02-14 18:13

I fully agree that this patch is nice addition to the custom rockbox settings, would be nice including it to standard releases.

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