Swap Left/Right Channels

[tertiorari]

Hi all,

I am trying to compile a custom build (Sansa Clip+) which has the left/right channels swapped, i.e. sound that should come out of the left earphone comes out the right, and vice versa.

I searched the forum and the clearest instructions I found were here:
http://forums.rockbox.org/index.php?topic=9939.0

Specifically,

But basically it is only one assembler line to change (for Sansa):

/firmware/target/arm/pcm_pp.c:
  change required in #ifdef HAVE_AS3514
    "mov r10, r10, ror #2\n\t" /* put left sample at the top bits */
  to
    "mov r10, r10, ror #18\n\t" /* put right sample at the top bits */

But this was posted three years ago, and in the current build, pcm_pp.c doesn't have that line. The closest I found was:

Code: [Select]

"mov r2 , r12, lsl #16\n\t" /* put left sample at the top bits */

What should I edit in the current build to effect this change?

[saratoga]

But this was posted three years ago, and in the current build, pcm_pp.c doesn't have that line.

The Clip+ doesn't have a PP cpu, so it doesn't use the code in pcm_pp.c.  Check the as3525 folder instead.

Edit:  its probably easier to just flip the samples somewhere in the DSP code rather then in a driver.

[tertiorari]

Should I be looking in

Code: [Select]

/firmware/target/arm/as3525/

or is that completely the wrong place?

[saratoga]

Should I be looking in

Code: [Select]

/firmware/target/arm/as3525/

or is that completely the wrong place?

Thats where the driver is, but as I said above its probably easier to just pick some random DSP feature and have it flip the samples when enabled.  Maybe make 100% stereo width flip the channels.  Or something else thats implemented in c code rather then assembly . . .

[tertiorari]

Ah, I understand. Good idea, thanks.