Rockbox Development > Feature Ideas

Is it possible to disable downsampling?

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andrew_a:
Hello guys!

I've got a rockboxed Toshiba Gigabeat F, and have an idea recently to take the digital signal from the processor and pass it to my standalone diy DAC (PCM 1742 KE) .
I like listening to hi-res and have all my music and lots of music to download in various hi-res formats.

So the question is - any possibility to simply disable downsampling to 16/44 ? - I've seen a similar topic here and read that there may be lots of problems with it.

And if not possible to just disable it - can the code be modified (by myself with your kind advices))) to output 24/96 instead of 16/44 ? all the time, all music - just switch the format - I suppose it must be much more simple than disabling conversion.. And yes, the Toshiba's DAC seem to support this bitrate/frequency.

Thank you! I like rockbox very much and want to use one of my favourite devices as a hi-res digital source.

Any thoughts/advices highly appreciated! :)

saratoga:
How do you plan to use that DAC? 

I guess if you can wire it in, you can clock it at whatever you want and then hack up the output to be whatever you want.  It already supports 44.1k and 48k. 

andrew_a:
If I understand you right (with my bad English)) - I want to:

1) hack the output from 16/44 to 24/96
2) take the digital signal from processor by wiring it out through the dock and right inside to my DAC to the input pins of 1742 KE chip (haven't checked it for compatibility yet, but suppose it should do)
3) to still be able to use internal DAC at new frequencies - maybe it would sound even better?

Thank you for such fast answer!

Can you help me please with hacking th format?

saratoga:

--- Quote from: andrew_a on November 15, 2013, 02:51:36 AM ---1) hack the output from 16/44 to 24/96
2) take the digital signal from processor by wiring it out through the dock and right inside to my DAC to the input pins of 1742 KE chip (haven't checked it for compatibility yet, but suppose it should do)

--- End quote ---

Get step 2 working first.  Thats the difficult step.  Then if you want, try 1.  Don't bother though until 2 is finished. 


--- Quote from: andrew_a on November 15, 2013, 02:51:36 AM ---3) to still be able to use internal DAC at new frequencies - maybe it would sound even better?

--- End quote ---

Right now, the driver says it can only do 22/44/88 khz.  My guess is that the clock dividers are not present for 24/48/96 frequencies, but perhaps that could be hacked in with enough effort.  The F port is ancient, i don't know all the details. 

But no, it won't sound better.  There is no performance improvement to running the clocks higher, it just wastes power. 

andrew_a:
Ok, got it, thanks!

I think I'll re-consider the need of connecting external DAC ... maybe there's an easier way to get a 24/96 source (buy another pc for example))

p.s. still wondering if it is very hard to hack the output? to 24/88 for example ? (isn't it just as simple as changing the values in the code? =)))

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