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Bluetooth sample rate

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I've got a question about sample rates in Poweramp. I understand, that Android prefers 48 KHz sample rate. Therefore, the output of the speaker is always 48 KHz. OS is Android 12, moto g30 phone. I do not use DVC or EQU.

I also have got bluetooth earphones, with fixed 44.1 KHz rate. But, in the system, they resample to 44.1 only as a last step, there is always a "middle" 48 Khz step. This happens with 3 different earphones over time, so not specific for particular model.

I attach the screenshots. First is, when I set the OpenSL output to 44.1 KHz manually. Second is, when I let the OpenSL output to the default "defined by the device" sample rate.

The result is the same when using AAudio or DirectHD, or when I use some od the developer options (disable HW acceleration etc.).

In the first case, a chain of "44.1-48-44.1" is reported. So the internal Android resampling does this up- and downsampling? In the second case, I upsample through SoX to 48 kHz, and then it gets downsampled to 44.1 at the last step.

1) is there a possibility to play 44.1 kHz on bluetooth directly in Poweramp?

2) what does the chain 44.1-48-44.1 actually do?

3) what is the best setting quality-wise? letting the chain, or upsampling by SoX and letting downsample at the end?

thank you for information.








Edited by jumpingjackflash5
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Could there be some global audio options on your device (e.g. Dolby Atoms) in the chain?

Not sure about Moto (Max will be able to confirm) but on my Samsung I can keep the sampling rate at 44.1 from the source file right through to the Bluetooth device. I do have DVC on, but that shouldn't make a difference (make sure you have Absolute Volume disabled in Android Developer Options if you do use DVC though).



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Thank you very much for answer.

Yes, I would like to have it as posted on your screenshot, but on my Moto it does not work so.

I even tried to disable the "Sound effects" system app, but nothing has changed. I had all effects switched off anyway.

There is no direct "Dolby Atmos" app on my Moto.

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@Yukito Yukazain your case the aac codec runs with this config (48khz/16bit). Poweramp (or any other player) can’t change codec or the codec parameters as this is negotiated between your phone and the bt device. Some minor adjustments could be done via phone Developer settings, though recent Androids always try to prioritize highest quality codes, and if aac chosen, no LDAC/LDHC is available anyway.

@jumpingjackflash544.1 -> 48 -> 44.1 means there are 2 extra resamplings within Android. Btw stock/AOSP/Pixel firmwares usually allow 44.1 kHz for bt codecs without extra 48 step. You can try AAudio or Hi-Res output and set 44.1khz there - it may help. 

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Thank you for answering.

The situation with AAudio or HIRES output is the same as OpenSL.

The thing with Adaptive Aptx (which my earphones do not support, btw) is probably that the output there can be 48 kHz, therefore the system downsampling to 44.1 is avoided.

If there is not other solution, I shall probably keep SoX resampling active, as the high quality upsampling and system downsampling from 48-44.1 is better than 2 system resampling.

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