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Bluetooth Codec Question

I am using a cellphone with Lineage 14 which is reported to be aptx and aac capable. The phone is aptx certified by qualcomm.
I am using a creative E% headphone amp and DAC as a bluetooth receiver for a small holiday system I haul about. It sounds quite nice but I have a question.

I am using AAC at no more than 256 which the E5 is supposed to receive and decode. Aptx would make me happy but less so. The E5 outputs optical stream to amps DAC so pathway is clean.

The problem is I don't know what codec is being used. I would like to know if the phone is sending AAC, aptx or SBC. Cant seem to find an app that will tell me what the two devices are communicating with.

So I was wondering are there any known killer samples for SBC and aptx that I could download to narrow down what is actually going out from the phone to the E5.

Any help appreciated. B

Re: Bluetooth Codec Question

Reply #1
Put a 20.5khz sin wave through as aac with the low pass disabled. Literally anything transcoding will remove ultrasound.

Re: Bluetooth Codec Question

Reply #2
OK. That's a place to start. I'll have to see if it bothers my dog or get my daughter to come over and listen though.  56 year old man  :(

So if its gone, how do I know if its aptx or SBC? I understand SBC is pretty poor but what I am hearing is quite nice actually.

Thanks though. How do I disable lowpass? I use T audio converter and qaac.  Thanks for your help. B

Re: Bluetooth Codec Question

Reply #3

Activate Developer options :

Enable Bluetooth HCI snoop log, connect your Bluetooth receiver and play a few seconds of music. Disable Bluetooth HCI snoop log.

Copy the log file (/sdcard/btsnoop_hci.log on your Android device) to your computer, install Wireshark, load the log file and filter packets with btavdtp.

You'll possibly see lines like theses :
Code: [Select]
Rcvd ResponseAccept - GetCapabilities - Audio SBC (16000 32000 44100 48000 | Mono DualChannel Stereo JointStereo | block: 4 8 12 16 | subbands: 4 8 | allocation: SNR Loudness | bitpool: 2..53)
Rcvd ResponseAccept - GetCapabilities - Audio non-A2DP (APT-X - 44100 48000, Stereo)
Rcvd ResponseAccept - GetCapabilities - Audio MPEG-2,4 AAC
(This happens when I connect a phone to a Sony MDR-ZX750BN)

Below these lines, I have :
Code: [Select]
Sent Command - SetConfiguration - ACP SEID [1 - Audio Sink] - INT SEID [1 - Audio Sink] - Audio SBC (44100 | JointStereo | block: 16 | subbands: 8 | allocation: Loudness | bitpool: 2..53)
because unfortunately my Nextbit Robin doesn't support aptX.

When I was connecting a Motorola moto E 2015 to the same cans, I got :
Code: [Select]
Sent Command - SetConfiguration - ACP SEID [3 - Audio Sink] - INT SEID [2 - Audio Sink] - Audio non-A2DP (APT-X - 44100, Stereo)

Hope it helps,



Re: Bluetooth Codec Question

Reply #4
 Thank you. I did see that and gave it a whirl, but the file log is nowhere to be found, sd card or otherwise. I should worry less. It sounds great for a vacation stereo. Its only going to be used for background and not critical listening.

It seems some type of app would be in order though now that there are so many codecs. I will wait for Lineage 15 and that will offer the option to select I guess. B

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