Bluetooth Sample Rates help General
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Junior Member 11 posts Acerun Junior Member 11 posts
Acerun
If I'm streaming a track whose quality is 16-bit/44.1KHz it looks like my Samsung phone may be upsampling to the Qudelix max rate because it "sees" the Qudelix can handle 24-bit/96 KHz/990.  Does that sound right?  

Follow up to that, if I change my settings in my Samsung to 16-bit/44.1KHz output I see that the Qudelix shows play at 44.1KHz.  Will this be higher quality than the "upsampled" 24-bit/96KHz?

Third observation.  Even though my Samsung output is set at 16-bit/44.1 KHz, Qudelix shows it is playing at 44.1KHz/24-bit/909.  Why does it show 24-bit when my phone is set to send 16-bit?  Also, when an "Ultra HD" song comes on, the Qudelix shows the same play rate of 44.1KHz 24-bit but Amazon Music HD shows "currently playing" at 44.1 KHz/24-bit and on some tracks 48KHz/24-bit.

Thanks
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Qudelix Support qudelix Qudelix 2,071 posts
Qudelix Support qudelix

Good question.

Bluetooth A2DP, every track is transcoded through a designated audio codec for transmission over Bluetooth.

For a 16-bit/44.1KHz source, the OS oversamples it to 96KHz and encoded it LDAC 96KHz. As we researched, the limited LDAC bitrate is wasted for the meaningless oversampled frequency region.

Thus, for any 44KHz source track, setting LDAC frequency the same as the source track, i.e. 44.1KHz, would provide the optimal sound quality since every LDAC bits are fully used for the active frequency band.

 

And 16-bit would be encoded with 8-bit or 16-bit zero paddings, depending on the bit resolution settings. Practically, LDAC 24 or 32 bit would provide the same sound quality. For 16-bit source track, those zero-padding would help to keep the resolution even at low source digital volume control. However, 5K provides 2-way associative absolute volume control, and the audio is always encoded at full precision.

 

Our recommendation for the optimal LDAC performance is that:

  • set LDAC frequency the same as the source track
  • set the bit resolution 32

 

Thanks~!
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raykkho Junior Member 8 posts
raykkho
Good info., but in my Oneplus 6T, 24/96 is the default for LDAC, setting it to system default only returns it back to 24/96, as soon as you switch to another app.
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Acerun Junior Member 11 posts
Acerun
I have to adjust the LDAC sample rate on my Samsung phone at the beginning of each listening session. No big deal for better SQ.
 
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raykkho Junior Member 8 posts
raykkho
qudelix1.jpeg  qudelix4.jpeg  qudelix2.jpeg  qudelix3.jpeg    

Can anyone advise why with the above settings, on both the phone Developers Mode USB, as well as the Qudelix app, I am still getting 24/44.1, instead of file's native format of 16/44.1?
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Acerun Junior Member 11 posts
Acerun
Mine does exactly the same.
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raykkho Junior Member 8 posts
raykkho
Acerun wrote:
Mine does exactly the same.


Intesting, wondering if this is what it is. 😊
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Acerun Junior Member 11 posts
Acerun
I don't know electronics enough but I think I read it one point that 24 bit is their base rate
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raykkho Junior Member 8 posts
raykkho
Will just follow their advice above to "simplify" things

"Our recommendation for the optimal LDAC performance is that:
  • set LDAC frequency the same as the source track
  • set the bit resolution 32"
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