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Ipod classic - rockbox - its happening. - Page 179

post #2671 of 3087
Quote:
Originally Posted by saratoga View Post

 

If by coax he means sp/dif, that will never happen since there is no sp/dif transceiver on the ipods.

 

There is USB though, so that could be used to drive a DAC.  Basically implement support for USB audio class devices, then the ipod would look like an ordinary PC to a USB DAC.  Seems fairly pointless though, as the line out and headphone out on the Classic are both exceptional, so I don't see anyone taking an interest in this.  

 

Again this is wishful thinking. It is not possible.

 

The only way to get a digital signal out of a Classic is through iAP (i.e. devices like the CLAS, Fostex etc.) which for technical reasons Rockbox cannot support with no change in sight.

post #2672 of 3087

Hello All,

 

Just Rockboxed my iPod Video (80GB) and testing out some hi-rez files. My 24/96 and 24/192 ALAC files play but pause to catch up (with decoding I suppose). Will they play better in FLAC or another lossless format? 24/48 ALAC play fine so I don't have a problem down converting them to 24/48 since my I won't "hear" the difference but if I don't have to that is preferable.I'll just get source files in FLAC ongoing if that solution works.

 

Thanks for your input.

post #2673 of 3087
Quote:
Originally Posted by cooperpwc View Post

 

Again this is wishful thinking. It is not possible.

 

 

Sure it is.  Its a software USB core, you can program it to do whatever you want.

 
Quote:
Originally Posted by cooperpwc View Post

The only way to get a digital signal out of a Classic is through iAP (i.e. devices like the CLAS, Fostex etc.) which for technical reasons Rockbox cannot support with no change in sight.

 

Are you quoting my own post back at me?  What I meant when I wrote that is that its not possible for us to write a driver that talks to iAP devices over USB because those use public key encryption to verify that the software and hardware are authorized.  But this limitation does not apply to ordinary USB DACs which do not use iAP (obviously, since you can use them with PCs or Android phones).  In that case you'd just need an adapter cable and the right software stack in rockbox.  

post #2674 of 3087
Quote:
Originally Posted by sparklyflea View Post

Hello All,

 

Will they play better in FLAC or another lossless format? 24/48 ALAC play fine so I don't have a problem down converting them to 24/48 since my I won't "hear" the difference but if I don't have to that is preferable.I'll just get source files in FLAC ongoing if that solution works.

 

 

FLAC is much faster yes, but everything is resampled to 44.1k (or 48k if you have that set) anyway.  My new hermite resampler is pretty good quality, but not nearly as good as sox or foobar, so its probably best to resample first.  Will certainly extend your battery life.  

post #2675 of 3087

Thx saratoga. Is the 44.1 or 48 output somewhere in the options somewhere or a default of Rockbox based on input file? I haven't found it in any option setting but I only had a little time to check out the software.

post #2676 of 3087

Its under playback settings > Frequency.

 

However you don't want to change this unless all of your audio is 48k, which is unusual.  44.1k is much more common.  

post #2677 of 3087
Quote:
Originally Posted by sparklyflea View Post

Hello All,

 

Just Rockboxed my iPod Video (80GB) and testing out some hi-rez files. My 24/96 and 24/192 ALAC files play but pause to catch up (with decoding I suppose). Will they play better in FLAC or another lossless format? 24/48 ALAC play fine so I don't have a problem down converting them to 24/48 since my I won't "hear" the difference but if I don't have to that is preferable.I'll just get source files in FLAC ongoing if that solution works.

 

Thanks for your input.

 

If you want to use high resolution audio on a Rockboxed iPod you need to compress to 16/44 or 16/48, I'm using XLD which is free, fast, and simple.  The iPod will accept 24/44 and 24/48 but only output at 16/44 and 16/48 (the same as a CD).  I was originally convinced that output was 24 bit, I was wrong it was just wasting space.  CD quality audio on a portable device is sweet.

post #2678 of 3087
Quote:
Originally Posted by jtaylor991 View Post

Hey guys. I Rockboxed in Jan or Feb and haven't updated since. Currently running version "93130beM-130110". Where should I update. I'm pretty sure I got this build from the aroldan dropbox. I was just in there and last update was 6 months ago, not long after I Rockboxed. Did something happen, am I missing something?


...

post #2679 of 3087
Quote:
Originally Posted by RUMAY408 View Post

 

If you want to use high resolution audio on a Rockboxed iPod you need to compress to 16/44 or 16/48, I'm using XLD which is free, fast, and simple.  The iPod will accept 24/44 and 24/48 but only output at 16/44 and 16/48 (the same as a CD).  I was originally convinced that output was 24 bit, I was wrong it was just wasting space.  CD quality audio on a portable device is sweet

This iPod is to be my hi-rez device. Ran out of room on it for my entire collection so thought I'd give Rockbox a go. I had read the iPod truncated the last 8 bits but it didn't seem to be definitive so wasn't sure. I'm happy to save space. Never felt/heard that poor little hard drive work so hard as it has since Rbox install. Thanks for the info.

 

P.S. I'm using Win7/64 so I'll find a suitable tool to convert, hopefully free. This hobby can sure get you in the wallet.


Edited by AladdinSane - 8/26/13 at 8:33pm
post #2680 of 3087
Quote:
Originally Posted by saratoga View Post

 

Sure it is.  Its a software USB core, you can program it to do whatever you want.

 

I stand by the proposition that the iPod Classic does not have that hardware capability.

 

Shall we hold our breath waiting for you to do this?  ;-)


Edited by cooperpwc - 8/26/13 at 9:25pm
post #2681 of 3087

About hi-rez files on a Rockboxed iPod:  I have an iPod Video 5.5 gen (originally 30GB) and an iPod Mini 2nd gen (originally 4GB).  Both have been upgraded to 128GB solid state via CF cards (the former using Tarkan's board).  I *play* 24 bit/96kHz files on them all the time in WAV format under Rockbox, but they are *downconverted* to a lower sampling rate, probably equal to the Frequency parameter described above.  I also tried high-rez ALAC but got skipping as well.  When you go with an uncompressed format like WAV, Rockbox on an iPod keeps up.  In fact, I can also use easily 7 bands of EQ and there's no skipping heard (although the interface slows down a lot). 

 

Now, about the playback itself:  I checked the frequency response of the playback via a simple log sine sweep out of the iPod Video line out for 44kHz, 48kHz, and 96kHz uncompressed WAV files.  What I found was nearly flat frequency response with 44.1kHz files, a slight drop-off in frequency response (say above 15kHz) with 96kHz files, and a more-severe drop off in frequency response for 48kHz files, all when playing back at 44.1kHz.  What that says to me is that Rockbox uses very simple interpolation to do the downconversion.  I didn't check the filter math or keep careful track of the dB drops, but I suspect it is linear interpolation. 

 

Bottom line:  You can load up 96kHz WAV files on a Rockboxed iPod and they will play.  There will be a very slight loss of high frequencies when you do, and you can decide for yourself by listening whether it is noticeable.  For me, the better mix on the 96kHz files makes them preferable to the older 44.1kHz files I have for those albums that I have in both formats (mostly Steely Dan/Donald Fagen).

post #2682 of 3087
Quote:
Originally Posted by jazzman7 View Post

 I didn't check the filter math or keep careful track of the dB drops, but I suspect it is linear interpolation. 

 

Bottom line:  You can load up 96kHz WAV files on a Rockboxed iPod and they will play.  There will be a very slight loss of high frequencies when you do, and you can decide for yourself by listening whether it is noticeable.  For me, the better mix on the 96kHz files makes them preferable to the older 44.1kHz files I have for those albums that I have in both formats (mostly Steely Dan/Donald Fagen).

 

It was linear until recently, now its cubic hermite.  You'd be wise to convert those 96k WAV files to 44.1k FLACs using a good quality resampler like in foobar.  Better battery life, better quality, and much smaller file sizes.

 

Quote:
Originally Posted by cooperpwc View Post

 

I stand by the proposition that the iPod Classic does not have that hardware capability.

 

Shall we hold our breath waiting for you to do this?  ;-)

 

Ah no thanks :)  


If I had a few tens of hours to throw at audio right now I'd probably work on something less futile than working around one perfectly good DAC for another, like fixing up Opus support so that it was faster.  But if somebody else wants to experiment, its a great opportunity to learn about the joy of USB programming.  

 

Quote:
Originally Posted by sparklyflea View Post

This iPod is to be my hi-rez device. Ran out of room on it for my entire collection so thought I'd give Rockbox a go. I had read the iPod truncated the last 8 bits but it didn't seem to be definitive so wasn't sure. I'm happy to save space. Never felt/heard that poor little hard drive work so hard as it has since Rbox install. Thanks for the info.

 

 

Well there is dither too, so you don't have to truncate.  But the DAC itself is limited to about 90 something dB by the analog, so running it in 24 bit mode would be pointless.  Think of the analog noise as free dither :)

post #2683 of 3087

I always run LOD to my amp if that makes any difference. I converted a few 24/96 ALAC to 24/96 FLAC using JRiver and they work without skipping but sounds like good ol' 16/44.1 may be the sweet spot.  Fun stuff. Thanks for all the helpful comments.

post #2684 of 3087
Quote:
Originally Posted by saratoga View Post

It was linear until recently, now its cubic hermite.  You'd be wise to convert those 96k WAV files to 44.1k FLACs using a good quality resampler like in foobar.  Better battery life, better quality, and much smaller file sizes.

Thanks for the info on the interpolation method, and agreed on all advantages.  I didn't trust the resamplers that I had access to when I first archived, though.  I'm also not so interested in dual libraries.  I do use the 96k files with other devices/DACs, and sometimes I grab them off of the iPods for convenience.  And as for file space, I've got plenty.

 

EDIT:  Thanks for your efforts on Rockbox!  The 10-band parametric EQ is what keeps me on Rockbox -- no other player comes close to it for EQ.  


Edited by jazzman7 - 8/27/13 at 5:38am
post #2685 of 3087
Guys, I know this is a thread for iPod Classics running Rockbox, but in my case, its an iPod Mini 2nd Gen. I feel its best I ask you guys, since my Mini is Rockboxed and you guys seem to know a lot about these things.

Anyways, my issue is that, although my Mini is fully charged, and has Rock box installed on it (as of yesterday), it all of a sudden cut out this morning during usage. I know it still has batteries because its only been replaced recently, and it was at 90% when I was using it this morning. I can plug it into my PC, and it will be recognised to the point where I can still transfer files, but the screen remains to be blank - no lighting, no nothing.

Any ideas what my problem may be?
Help/advice is greatly appreciated!

Cheers.
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