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48kHz file was downsampling to 44kHz on Bluetooth


SuperToy
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That does seem strange, the BT device is obviously capable of 48kHz so I don't know why the interim processing is resampling down to 44.1.  Does enabling or disabling DVC for Bluetooth and/or the Absolute Volume dev option make any difference? Otherwise I think we'll need @maxmp's thoughts on this one.

Andre

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1 hour ago, andrewilley said:

That does seem strange, the BT device is obviously capable of 48kHz so I don't know why the interim processing is resampling down to 44.1.  Does enabling or disabling DVC for Bluetooth and/or the Absolute Volume dev option make any difference? Otherwise I think we'll need @maxmp's thoughts on this one.

Andre

Enable/disable DVC and Absolute volume in developer options make no difference. It's still 48 -> 44 -> 48 kHz conversion, with Float32 DVC.

I don't know how to completely turn off DVC for Bluetooth.

USB DAC and built-in speaker DVC are off, but Bluetooth DVC is Float32 DVC.

For 48 kHz aptX, the conversion is 48 -> 44 -> 48 kHz, and caused a little distorsion. Very little distorsion. But I think it may be better to not convert it.

For 96 kHz LDAC, the conversion is 48 -> 96 kHz.

aptX DVC.jpg

Edited by SuperToy
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These are the devices I use

- Built-in speaker : Huawei Mate20 X EMUI 10.1.0 (Android 10)

- USB DAC : Huawei CM-Q3 USB-C headset noise cancelling 3.

- aptX : Avantree Clipper Pro and Avantree Roxa Plus.

- LDAC : Sony SRS-X33 bluetooth speaker.

- Poweramp app : Beta v3-build-884-arm64-play (paid)

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5 hours ago, andrewilley said:

If setting BT to 96kHz works better for you, I'd use that. 48k>96k is a simple doubling, so probably the cleanest upscale you'll get.

Andre

All my aptX Bluetooth receivers support up to 48 kHz. I connect it to a wire headset to make it wireless for daily uses. LDAC is in Sony speaker, not a Bluetooth receiver.

I don't understand why Poweramp has to convert 48 kHz file to 44 kHz and convert back to 48 kHz again.

Actually, it's not a big problem. I don't have much 48+ kHz files. Just noticed that it has little distorsion and not good quality as 44 kHz file when playing via aptX. And I had just found Poweramp's Audio Info window and saw strange conversion in it.

P.S. Sorry about my English.

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I did more investigation. I forced Bluetooth sampling rate to 44, 48, 96 kHz in Developer options. And I saw the problem may be DSP (or Float32 DVC for Bluetooth) which is not support 48 kHz, so Resampler do downsampling 96 and 48 to 44 kHz and causes bad distorsion.

Bluetooth (DSP Volume Control = Float32) : 96 kHz (LDAC)
- FLAC 96 kHz : Resampler = no , DSP = 96 , Output = 96
- FLAC 48 kHz : Resampler = 48->96 , DSP = 96 , Output = 96
- FLAC 44 kHz : Resampler = 44->96 , DSP = 96 , Output = 96

Bluetooth (DSP Volume Control = Float32) : 48 kHz (LDAC & aptX)
- FLAC 96 kHz : Resampler = 96->44 , DSP = 44 , Output = 48 (This should be 96->48 kHz)
- FLAC 48 kHz : Resampler = 48->44 , DSP = 44 , Output = 48 (This should be no resampling)
- FLAC 44 kHz : Resampler = no , DSP = 44 , Output = 48 (This is OK, but the Resampler should be 44->48 kHz upsampling?)

Bluetooth (DSP Volume Control = Float32) : 44 kHz (LDAC & aptX)
- FLAC 96 kHz : Resampler = 96->44 , DSP = 44 , Output = 44
- FLAC 48 kHz : Resampler = 48->44 , DSP = 44 , Output = 44
- FLAC 44 kHz : Resampler = no , DSP = 44 , Output = 44

 

USB DAC (DSP Volume Control = None) : 48 kHz (Huawei CM-Q3)
- FLAC 96 kHz : Resampler = 96->48 , DSP = 48 , Output = 48
- FLAC 48 kHz : Resampler = no , DSP = 48 , Output = 48
- FLAC 44 kHz : Resampler = 44->48 , DSP = 48 , Output = 48

Edited by SuperToy
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