Xduoo x3

[mrp]

hmm weird but it's working I used the daily build and it seems to be fine ... thx a lot !!

[jkn]

(I'll try posting here but would be happy to told of a better place - it might not be X3-specific)

I have an X3 which I seem to have bot in a funny state. It was a while ago and I am revisiting it now, so I am not fully sure how it happened.

I have Rockbox on an SDcard and with the lock switch set to UNLOCKED I can boot to RB fine. But if try to boot to the stock firmware (switch LOCKED), nothing happens, the screen stays blank.

Presumably there is a problem with the bootloader?

I would like to have the option to boot to stock (accessing 2nd SDcard, and USB access seems better). But I think this needs me to boot the stock firmware to update the bootloader ... which I can't do.

What are my best options here please? Thanks a lot

[jkn]

D'oh - strike the above - I got it sorted. Typically, not long after making the posting.

I ended up getting X3-USBBurntool working; it was a bit of a faff because I had to do it under a VM, and getting the USB drivers etc. installed took a while. But I am back where I want to be.

Apologies for the noise.

[speachy]

I ended up getting X3-USBBurntool working; it was a bit of a faff because I had to do it under a VM, and getting the USB drivers etc. installed took a while. But I am back where I want to be.

I'm glad you managed to get X3-USBBurntool working and recovered the OF on your unit.

But given that rockbox doesn't touch the onboard flash at all, it's most likely that the flash was corrupted by something within the OF itself.

(BTW, recent dev builds should be _faster_ with respect to SD and USB operation than the OF, and exporting/mounting both SD cards WorkForUs(tm) just fine too..)

[RomanB]

Hallo
I have a one question. I would like to ask if somebody else noticed issue with audio quality with sample rate 44,1kHz. If I compare it with original firmware there is noticable less treble and less details. Old XVortex version of Rockbox sound similar like original firmware (better then last versions, I have on one SD card XVortex version and on second SD new version). It is also very easy noticable if you have file with sample rate 88kHz and switch it to 44kHz, but this problem is also with original files 44kHz. I listen on senn HD600 with external headamp (through line out from xDuoo X3).  Sorry for my English..

[saratoga]

^^^ usually more helpful if you get a 3.5 mm cable and measure the output in RMAA. The it is obvious what is wrong.

[speachy]

I suspect what's going here is that rockbox currently enables the de-emphasis filter of the X3's CS4398 DAC.

(see https://statics.cirrus.com/pubs/proDatasheet/CS4398_F2.pdf, section 7.3.2)

Whether or not this is "correct" is a matter of how the source material was mastered, but generally speaking, if it was mastered for CDs or DAT (ie just about everything) then use of this filter is appropriate (and expected!) to bring the frequency response back to neutral. 

I'm willing to change this, but first I'm going to need to see some sort of test evidence (eg a total sweep run through RMAA) that shows that this behaviour is wrong..

In the mean time, Rockbox has a built-in equalizer function that you can use to tune the output to your liking.

[speachy]

I'm willing to change this, but first I'm going to need to see some sort of test evidence (eg a total sweep run through RMAA) that shows that this behaviour is wrong..

To follow up to myself, it seems that "modern" [1] audio CDs rarely use pre-emphasis, so this filter probably shouldn't be enabled by default.

[1] loosely meaning "mastered digitally", ie not from an analog recording.   Nearly everything since the late 80s qualifies, with the notable exception of classical music which still tends to be pre-emphasized.

[RomanB]

Yes. I can corfim that this issue was the de-emphasis filter. Now it sounds OK (i am not able notice any difrence between original and rockbox). I read taht this re-emphasis filter used to be aplay on very old CD with only 14 bits resolution. I think that it is not necessary have this optional turn it on..  Thank you very much for your quick solution.

[RomanB]

I have one more question. How it is with hi-res 24bit files. Are they converted to 16bit before sending to DAC or full path is 24 bit?

[RomanB]

Also there is still problem with 192kHz (also 176,4kHz) files. Some of them are skip, some of them „only“ crackle, and sometime xDuoo X3 use complete to freeze.  Maybe if there is not posible alocate more memory (or other necesseary sources), would by better switch them automaticaly to 96 or 88kHz (if I swith frequency manualy then crackle is away, but skiping fiels are still skipping).

[saratoga]

I have one more question. How it is with hi-res 24bit files. Are they converted to 16bit before sending to DAC or full path is 24 bit?

Decoding is done at 32 bit precision but everything is dithered down to 16 bit for playback because we never had a device that could actually play back the 17bit or greater above the noise floor. Adding support for this would be neat, but would make little difference in practice.

Also there is still problem with 192kHz (also 176,4kHz) files. Some of them are skip, some of them „only“ crackle, and sometime xDuoo X3 use complete to freeze. 

Depending on the format, the CPU is probably not fast enough to decide those files, respect on MIPS where there are few cosec optimizations. The test_codec tool can be used to benchmark codecs, although it forces you to compile your own build.

[johnb]

I confirm the crackle @ 192kHz. I checked the Buffering Thread in the debug menu. The bar is always >= 95%, i.e. constantly refilling. I suppose this is what keeps the device too busy.

Edit: the X3 only shows PCM (which for the X3ii also is always close to 100%).
The other two bars in the X3ii are not shown for X3.

Edit2: Not that I care too much about such sampling rates ...

[speachy]

Also there is still problem with 192kHz (also 176,4kHz) files. Some of them are skip, some of them „only“ crackle, and sometime xDuoo X3 use complete to freeze.  Maybe if there is not posible alocate more memory (or other necesseary sources), would by better switch them automaticaly to 96 or 88kHz (if I swith frequency manualy then crackle is away, but skiping fiels are still skipping).

The reason for the "crackle" at higher data rates is that the the X3 can't keep the audio codec fed under high loads -- by the time we are able to start servicing the interrupt that tells us the audio buffer needs more data, it's already too late.

(Basically, we need double-buffered DMA at the hardware level, and the DMA controller in the jz4760 does _not_ support this.. but their newer SoCs do.  There are some other games we can still try to work around this but they all require a significant rework of the low level asm interrupt handling)

[RomanB]

Hallo
I would like to ask if bootloader are the same like Vortext version or if it is new one. I noticed in „major changes“ these sentence: „2021-08-26: xduoox3: Disable bootloader USB mode entirely, Bootloader improvements“. But the rockbox utility (1.5.1 and 1.5.0) shut down (without any error message) after I try install bootloader.  I think that it is the same problem like in this article: https://www.reddit.com/r/rockbox/comments/10quizp/help_installing_on_xduoo_x3/