BlueFruit Bluetooth to create audio device
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- Mixer
- Posts: 12
- Joined: Wed Dec 23, 2009 10:39 pm
BlueFruit Bluetooth to create audio device
Can I use this to receive Audio from a device? Ie. I want to be able to send music from my phone to this device and output that audio to the AUX jack on my vehicles radio.
- adafruit_support_mike
- Posts: 67454
- Joined: Thu Feb 11, 2010 2:51 pm
Re: BlueFruit Bluetooth to create audio device
Nope. It isn't fast enough.
Realtime digital audio needs about 44,000 samples per second to cover the human audio range. The EZ-Link's top speed is 230400 baud, which is roughly bits per second, but there's a certain amount of connection overhead. It's easiest to assume 10 baud = 1 byte. That translates to about 23,000 samples per second.. about half as fast as it needs to be.
Not only would you lose the whole upper half of the audio spectrum, you'd also run into problems with 'aliasing'.. basically all the high input frequencies would get folded around the 11.5kHz center frequency. An input tone starting at 1Hz and rising to 20kHz would produce output that rises to 11.5kHz then falls back to 8.5kHz. Music passing through a system like that would sound seriously wierd.
Realtime digital audio needs about 44,000 samples per second to cover the human audio range. The EZ-Link's top speed is 230400 baud, which is roughly bits per second, but there's a certain amount of connection overhead. It's easiest to assume 10 baud = 1 byte. That translates to about 23,000 samples per second.. about half as fast as it needs to be.
Not only would you lose the whole upper half of the audio spectrum, you'd also run into problems with 'aliasing'.. basically all the high input frequencies would get folded around the 11.5kHz center frequency. An input tone starting at 1Hz and rising to 20kHz would produce output that rises to 11.5kHz then falls back to 8.5kHz. Music passing through a system like that would sound seriously wierd.
- jhlink
- Posts: 1
- Joined: Sun Jan 31, 2016 7:11 pm
Re: BlueFruit Bluetooth to create audio device
Hey Mike!adafruit_support_mike wrote:Nope. It isn't fast enough.
Realtime digital audio needs about 44,000 samples per second to cover the human audio range. The EZ-Link's top speed is 230400 baud, which is roughly bits per second, but there's a certain amount of connection overhead. It's easiest to assume 10 baud = 1 byte. That translates to about 23,000 samples per second.. about half as fast as it needs to be.
Not only would you lose the whole upper half of the audio spectrum, you'd also run into problems with 'aliasing'.. basically all the high input frequencies would get folded around the 11.5kHz center frequency. An input tone starting at 1Hz and rising to 20kHz would produce output that rises to 11.5kHz then falls back to 8.5kHz. Music passing through a system like that would sound seriously wierd.
It's almost two years, and I'm hoping this might still be possible with hopeful advances in bluetooth tech! :)
I just wanted to confirm, but even for devices like the Adafruit Bluetooth LE SPI Friend or the Bluefruit LE Micro, this still wouldn't be possible, right?
If it isn't, is baud rate still the preventing factor?
For example, I think for the SPI Friend, data can transfer as fast as realistically possible between the device and a host microcontroller, but the bottleneck then becomes BLE's maximum speed limit. I think this is also the same for the Bluefruit LE Micro, since I'm guessing that the Atmega32u4 can handle high data speeds with the nR51822 chip.
---- EDIT ----
I think I found my answer. Just for future notice, I don't think the nR51822 chip can support audio. It just wasn't built for it.
I've done a little more digging, and it's the RN-52 chip that me and Mixer is probably looking for.
:(
Thanks!!
James
- adafruit_support_mike
- Posts: 67454
- Joined: Thu Feb 11, 2010 2:51 pm
Re: BlueFruit Bluetooth to create audio device
BLE isn't even close to fast enough. It's designed to be a low-speed protocol, and I think the theoretical maximum bitrate is about 25k per second.
Bluetooth Classic is still where it was two years ago: not fast enough to stream audio directly, so you have to compress before sending and decompress upon receiving.
Bluetooth Classic is still where it was two years ago: not fast enough to stream audio directly, so you have to compress before sending and decompress upon receiving.
Please be positive and constructive with your questions and comments.