Re: Can earphones be paired with two sound-producers at the same time, like the pc and the phone?

On 2/14/2022 4:40 AM, micky wrote:
> This is the essential part of a longer post (soon to be released at
> major theatres).
> 
> This relates directly to cell phones.
> 
> So to turn off the built-in PC speakers I disabled them but no sound
> comes from the Bose bluetooth hearphones even though they are still
> listed as paired with the PC, although the phone also says that the
> hearphones are paired with it!!!
> 
> Can they be listed as paired, either on the phone or the PC, but not
> really be connected?  Or can speakers or earphones be paired with two
> sound-producers at the same time, like the pc and the phone?   Will both
> sounds come out at the same time, overlaying each other?      (The phone
> isn't making any sound now anyhow, and I don't want to fiddle because
> the medical clinic is supposed to call right back.)
> 
> 
> And now I just got bu-dup bu-dap-dup in my ears and I don't know who
> sent it or what it means.  Nothing on the PC screen or the phone gives a
> clue. I thought maybe the hearphones were turning off but they haven't.
> 
>   the built in speakers are still there and they are now listed as the
> default, and now that I got a phone call, removed the hearphones (which
> turn themslves off if neither ear has one.)

One headset cannot listen to two PCs at the same time,
because each PC has its own spread spectrum frequency hopping
pattern. It would take two radio chains, to do a good job in
your proposed design. The easiest way to do it, would be
for the headset to have two BT chips (one radio chain per chip)
and mix the audio together from the output of the chips.

Of course, no one would build that, because the battery life would
be affected.

I tried to run two BT audio devices off the PC, and I wasn't allowed to
do that. Even though Windows allows the Mixer to be bypassed, and you
can output two music streams to two speaker systems at the same time.
Winamp was always touted as the beast for this, but I've never got
any further at evaluating that idea.

I haven't tried running two dongles on the PC at the same time.

*******

And this is a hell of a lot more info, than you'd get from BT
Marketing Material.

https://en.wikipedia.org/wiki/Channel_access_method

    "As an example, the Bluetooth communication system is based on a
    combination of frequency-hopping and either

        CSMA/CA statistical time-division multiplexing communication
        (for data communication applications) or                      [CA=Collision Avoidance]

        TDMA (for audio transmission).  [Time Division Multiple Access]

     All nodes belonging to the same user (to the same piconet) use the
     same frequency hopping sequence synchronously, meaning that they
     send on the same frequency channel, but CDMA/CA or TDMA is used
     to avoid collisions within the VPAN. Frequency-hopping is used by
     Bluetooth to reduce the cross-talk and collision probability between
     nodes in different VPANs.
    "

https://en.wikipedia.org/wiki/Time-division_multiple_access

    "In dynamic time-division multiple access (dynamic TDMA), a scheduling
     algorithm dynamically reserves a variable number of time slots in each
     frame to variable bit-rate data streams, based on the traffic demand
     of each data stream. Dynamic TDMA is used in ... Bluetooth"

Knowing a bit of the back story, makes it easier to predict what
functions it could have. In this case, it didn't help much.

*******

BT is allowed to do more than just "run your audio stream for you".
If it wants to beep or burp, it can. When it wants to pair, it
can make a pairing noise. My little BT speaker has a couple of
tonal patterns it uses, as well as a flashing LED.

    Paul