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Support and General Use => Hardware => Topic started by: Alex_Nsk on April 10, 2009, 12:25:54 AM

Title: X5 total audiophile remode. BIG Question for the programmers- authors of builds.
Post by: Alex_Nsk on April 10, 2009, 12:25:54 AM
Hi everybody! I'm new member of rockbox forum from Siberia, Russia!
I'm happy owner of rockboxed + flashmoded Cowon X5.
Some pictures 'bout modifications can be seen here: http://www.player.ru/talk/showthread.php?t=59891
And now I working to reach the best possible sound with this item..
Right now I can connect X5 throu I2S@16bit bus to the my home audiophile multibit  DAC, it sounds great, but I want more audiophile sound on a walk mode...
I plannin to made a little board whith brand new audiophile DAC & powerfull headphone amp, and put it inside the X5L instead of it's second little battery.
To reach the best possible sound I'm plan to use TI PCM1798 + AD8620 buffers + TPA6120 headphones driver.  PCM1798 can work with up to 24bit*192kHz input PCM.

So my question is: is it possible to cansel limit on 16bit PCM words output from the Coldfire CF5250? There are 32-bit floatin point arithmetics inside of this chip, but PCM output is strong limited to 16bit. This leads to many errors in LSBs when using DSP routings (pre cut, EQ and so on..) in 32bit format and downsampling it to 16bits output (that is why ditherin option available there)
By the way, codec already used  in X5 (TI TLV320) is ready to work with 24 bit words, but this possibilities is ommited.

Is it possible to made the "audiophile grade" build for X5 where output PCM format  from CF5250 will 24bit I2S?
Is it possible to made the "audiophile grade" build for X5 where all DSP routins wil be ommited?
Title: Re: X5 total audiophile remode. BIG Question for the programmers- authors of bui
Post by: saratoga on April 10, 2009, 10:35:46 AM
Right now I can connect X5 throu I2S@16bit bus to the my home audiophile multibit  DAC, it sounds great, but I want more audiophile sound on a walk mode...
I plannin to made a little board whith brand new audiophile DAC & powerfull headphone amp, and put it inside the X5L instead of it's second little battery.
To reach the best possible sound I'm plan to use TI PCM1798 + AD8620 buffers + TPA6120 headphones driver.  PCM1798 can work with up to 24bit*192kHz input PCM.

Neat project.

So my question is: is it possible to cansel limit on 16bit PCM words output from the Coldfire CF5250? There are 32-bit floatin point arithmetics inside of this chip, but PCM output is strong limited to 16bit.

Its actually not floating point internally.  Rockbox doesn't use FP at all.  But assuming your chip can handle 24 bit words, I don't see why you couldn't output at 24 (or even 32 bit) with some changes to the code.  The playback engine would be ok with it, we currently don't just because don't have any devices with good enough DACs to take advantage of it.


Title: Re: X5 total audiophile remode. BIG Question for the programmers- authors of builds.
Post by: Alex_Nsk on April 12, 2009, 10:08:51 PM
Unfortunatelly, i just haven't any knowleges in programmin'...So, could you be patient  to help me with such modifications? I'm needed in limits of 24 bit output words, nothin' else...Just a thought: there are possible must to be changed dithering formulas??

So, technical task sound in this way: output from Coldfire chip must be in 24bit I2S format (exept of 16bit I2S novaday) for all supported input formats, regerdless it's bit depth. Doing' so all downsampling errors will be shifted to the LSB of 24bit words (256x down in amplitude).

BIG Thanks anyway!

Hey, ANYBODY???
Title: Re: X5 total audiophile remode. BIG Question for the programmers- authors of builds.
Post by: Llorean on April 14, 2009, 05:40:14 PM
Since this is something specific to your hardware modification, you're probably going to have to do the programming yourself. That means it's time to start learning. :)
Title: Re: X5 total audiophile remode. BIG Question for the programmers- authors of builds.
Post by: saratoga on April 14, 2009, 05:43:48 PM
Unfortunatelly, i just haven't any knowleges in programmin'...So, could you be patient  to help me with such modifications? I'm needed in limits of 24 bit output words, nothin' else...Just a thought: there are possible must to be changed dithering formulas??

I don't know how your hardware works, so you'll have to figure that out yourself.  And if you output at 24+ bit you would disable dithering.
Title: Re: X5 total audiophile remode. BIG Question for the programmers- authors of builds.
Post by: Alex_Nsk on April 14, 2009, 10:18:53 PM
Im specialist in hardware not in soft !  :'(
All what I'm askin for - to make a build for X5 in wich output format to the codec is 24bit I2S exept 16bit I2S. Dithering must stay as is but might work with 24bit words.

GOD WILL SEE YOUR COOPERATION!!!
 I'LL TELL HIM MYSELF!
SO...PLEASE, HELP!!!!!!!!
 :)
Title: Re: X5 total audiophile remode. BIG Question for the programmers- authors of builds.
Post by: AlexP on April 16, 2009, 08:21:19 AM
Don't hold your breath.
Title: Re: X5 total audiophile remode. BIG Question for the programmers- authors of builds.
Post by: Alex_Nsk on May 13, 2009, 10:15:54 PM
My hardware come to the logical ending...could anyone help me with my problem? Degrading of the sound when turn-in the DSP module on (as a pre cut) clearly hears right now (with slight modification of X5 only)
It is so sad than nobody don't want to cooperate... :-\
Title: Re: X5 total audiophile remode. BIG Question for the programmers- authors of builds.
Post by: Bagder on May 14, 2009, 01:56:20 AM
You make custom hardware. (which only you then have)

You claim 24bit is "necessary" (while the entire rest of the world can't tell the difference between 16bit 200kbit mp3 and a CD)

You then make vague requests on a users forum about wanting help to adjust the software. Somehow.

It would be a lot of work for a developer for you only for free, for hardware that developer doesn't have.

... and then you are surprised nobody takes the bait?

(Updated: spelling!)
Title: Re: X5 total audiophile remode. BIG Question for the programmers- authors of builds.
Post by: Alex_Nsk on May 15, 2009, 01:25:07 AM
It's software mods is THE must for any cowon X5 owner!
Audio codec used in X5 (TLV320avic23) could work with 24 bit input format.
When using rockbox soft it is clearly hear degradation of perceived sound when turning on ANY DSP function which decrease a total volume (such as EQ cutting, precut and so on) because of loss of information in LSBs. I think it could occur because of rounding errors when downscale 32bit words to the 16bit ones.
If PROGRAMMERS OF X5 Rockbox utility could share internal words to the 24 bit limits it lifts up the quality of sound for every user of cowon X5 with or without hardware modifications I do. Not for me only!
Title: Re: X5 total audiophile remode. BIG Question for the programmers- authors of builds.
Post by: GodEater on May 15, 2009, 05:06:49 AM
I think you really have to accept that you're the only person interested in this. I certainly have no interest in improving the sound quality of my DAP - it's perfectly acceptable to me as it is.
Title: Re: X5 total audiophile remode. BIG Question for the programmers- authors of builds.
Post by: Alex_Nsk on July 09, 2009, 01:57:57 AM
Hi for all HEAD-FIERS!!!
1st July is the birthday of my aleXmod audiophile project.
It is a cowon X5L in which second battery was detached and in it's place new plate with audiophile DAC+AMP combo was installed.
My aleXmod sounds just terrific good with Senn HD580 headphones, but with my second (portable) pair of Sleek-Audio SA-6 it is too much loud (aprr 200mW per Chanel I estimate)
So I must to decrease a volume in digital domain by appr -12..-16dBs depending of the material (it is easy to do with eq enable and use "pre-cut" for this)
I dislike a possible degradation of sound due to rounding errors  when downsamplin 32bit words to the 16 bit PCM.
So could anyone interested in my project help me with solving of such software limitation and made a built in which  from CPU goes 24bit PCM to the DAC circuit. For doing this I could sent a plate for this hardware mode
as a present...
By the way, I have some such plates for DIYers if anyone interested - just write me!
Title: Re: X5 total audiophile remode. BIG Question for the programmers- authors of bui
Post by: macgeek417 on July 10, 2009, 07:18:59 PM
Honestly, while I can tell the differance between a 128k and 192k mp3, I don't see why one would waste disk space with FLAC or anything.

And you are worried about 32-16 bit downsampling? I thought CDs were only 16bit 44.1khz PCM audio, so what's the point of a 32bit audio file?
Title: Re: X5 total audiophile remode. BIG Question for the programmers- authors of builds.
Post by: Alex_Nsk on August 27, 2009, 11:01:35 PM
Inside X5's CPU all digital audio words presented in 32 bit format: 16bits of DATA + 16bits of nulls in LSBs. When performing DSP function such as EQ, PRECUT, CROSSFEED etc this words could be multiplied and divided by different digits. So when performing such operations (decreasing the volume in PRECUT for example) a part of DATA bits shifted down in 32 words (just below upper 16 bits). And after rounding such words from 32bit format  to the 16 bit format we have a DATA stream in which all LSBs is just neglected. Such lossless MUSIC sounds MP3 alike with the absence of all microdetails. Just lifeless
By the way, my project  stay alive, sounds GREAT! )))

Waiting for the rockbox patch when forementioned problem is solved, it will made by one of the "aleXmod" X5 owner...
If anybody interested in true audiophile sounding aleXmoded X5 - just stay tuned!
Title: Re: X5 total audiophile remode. BIG Question for the programmers- authors of bui
Post by: saratoga on August 28, 2009, 12:17:36 AM
Inside X5's CPU all digital audio words presented in 32 bit format: 16bits of DATA + 16bits of nulls in LSBs.When performing DSP function such as EQ, PRECUT, CROSSFEED etc this words could be multiplied and divided by different digits. So when performing such operations (decreasing the volume in PRECUT for example) a part of DATA bits shifted down in 32 words (just below upper 16 bits).

No internally its stored in full 32 bit, no padding required, although codecs can pad if they return less then 32 bit precision.

And after rounding such words from 32bit format  to the 16 bit format we have a DATA stream in which all LSBs is just neglected. Such lossless MUSIC sounds MP3 alike with the absence of all microdetails. Just lifeless

You've been saying things like this for a while now and I guess not understanding what people are trying to say to you.  Let me be blunt:  what you are saying is absolutely a load of shit.  It makes zero sense and I'm as baffled as everyone else that you could be knowledgeable enough to modify your X5 while being so clueless about audio.  Dithering to 16 bit vs. 24 bit does not matter.  No one has added something like this because its useless.  Any loss of detail is in your head. 

Stop worrying about it.