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Bluetooth
So as you can tell I like bluetooth a lot. Here's a question though.
I have a logitech bluetooth keyboard and mouse. I also have a bluetooth motorola stereo headphones (i believe they are the HS820). They pair and work out fine, but when I go to play a song, they are incredibly staticky and my mouse and keyboard go nuts. Typing is very erratic as well as the mouse movements. From my knowledge of bluetooth technology, this isn't suppose to happen. So why is it? And what can I do to eliminate this interference? |
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Bluetooth
Bluetoothguy wrote: So as you can tell I like bluetooth a lot. Here's a question though. I have a logitech bluetooth keyboard and mouse. I also have a bluetooth motorola stereo headphones (i believe they are the HS820). They pair and work out fine, but when I go to play a song, they are incredibly staticky and my mouse and keyboard go nuts. Typing is very erratic as well as the mouse movements. From my knowledge of bluetooth technology, this isn't suppose to happen. So why is it? And what can I do to eliminate this interference? A quick glance at this page, suggests Bluetooth is well armed for dealing with RF problems. http://www.mit.edu/~ddaly/projects/b...frequency.html What it cannot protect you against, is things outside the Bluetooth standard. Say your Bluetooth transmitter is fed by USB - will the USB always be ready when needed ? According to this, audio uses Synchronous Connection Oriented channels (which in other places would be called CBR or constant bit rate). http://pegasus.cc.ucf.edu/~rmccrave/...gnsolution.htm http://en.wikipedia.org/wiki/Bluetooth On the face of it, it looks like it should all work. A piconet can supply more nodes than you are using, so that is not the problem. Bluetooth supports SCO and ACL channels - the audio would be SCO, and the ACL would have to steal whatever time slots or holes that are left. It means the Bluetooth keyboard and mouse, have to honour the higher priority SCO requirements of the audio node. The scariest part of Bluetooth, is trying to figure out what version of standard every component you own, has been designed to. Many times I read a description of the way something works, and then I see mention of yet another "profile", and it leaves me wondering if the description I just read, is the way it works or not. If your Bluetooth dongle is plugged into a USB port, look at the port for a moment. USB ports are in stacks of two. If you plug the Bluetooth dongle into one port of a stack, try leaving the other USB hole blank. Just on the off chance, that other async activity on the USB port, may be interfering with timely delivery of data to Bluetooth. The Wikipedia article mentions this: "Most bluetooth stacks implement the SCMS-T copyright protection" and that makes me wonder whether a very low quality standard is being used to send audio to the headphones. Does the audio sound better if it is sourced by a cellphone ? This stuff isn't complicated enough... Yeah, I know, users aren't supposed to need to debug this stuff. The data rates involved are low enough, that there really shouldn't be a problem. The erratic behavior almost suggests the devices aren't all working to the same standard. Phone up Motorola tech support and ask them what's up ? And if you like to research these things for yourself, try recording the audio coming from the headset. Use a program like Audacity, to send a sine wave (tone) over Bluetooth. Use another program or a separate computer, to record the audio. Compare the sent and received waveforms, and inspect them for phase shifts, time shifts, waveform "flat spots" caused by data underrun, and so on. Ideally, you would want to open up the headphones and pick up the analog signal feeding the earpiece, to get a more accurate picture of the signal coming from the output of the Bluetooth receiver chain. Now, wouldn't an Ipod make this easier ? Paul |
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