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2011-10-17, 14:08
Dear XBMC Community,
I already searched the forums for the following question, but I did not find any answer.
For using my external amplifier I'd like to deactivate the internal (digital) Volume Control and instead use a microcontroller, which controls the volume via a PGA2311 between the PC and the amplifier. This should maximize the signal/noise ratio and improve the dynamical range of the sound card.
For this I'd like to archieve:
1. Control the Volume via XBMC and XBMC Commander from iPod/iPhone
2. LEAVE the volume at Max Level in XBMC
3. Send a signal VIA RS232 to the controller
4. Optional: Receive input from the controller and show the "real" volume in XBMC
I'm not sure how to achieve this behaviour. Is it possible to catch Volume events in some Python Script? Do I need to write a new Plugin?
Thanks in advance,
Rob
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I love to see how you do this ...
I was able to do something like this (not the best way) ... but I had to do it in windows and I was using a PS3 blue tooth remote.
I was using a app I found on the forum to interface with the ps3 remote, then I set one of the keys to a hot key for a little app to talk to my microcontroller instead of mapping it to the volume in the xbmc enviroment
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2011-10-25, 14:12
(This post was last modified: 2011-10-25, 14:15 by newcmbx.)
Hi,
thanks for your support so far. I am using Windows at the moment, because I am testing XBMC on my main computer, but if there were any advantages in using Linux I'd be open for that, too. I'll need some time to check out on JSON-RPC and the Event Server. After that, there will most certainly be further questions.
cu
newcmbx
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A fully digital volume control (even with an analog amp) is not generally bad. If you have a 16 Bit signal, which is common for CD-audio, and you are using a 24Bit Soundcard, you can use the odd 8Bit (in reality it is less, because the noise floor is usually bigger than the least significant Bit at consumer products) for your Volume control without loosing any Dynamic Range. The important point is where the volume control is done. In my case there will be some signal processing between XBMC and the audio output of the sound card. A volume control should be the last step in the signal processing, so it had to be outside of XBMC anyway. Based on this thoughts a analog volume control seems for me to be the most versatile solution. Furthermore it seems to be the cheapest and most feasible solution due to my personal skills.
best regards
newcmbx
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what would be interesting now is how volume control in the OS actually works. If it directly talks to the sound card, instead of manipulating the data stream, then it would be up to the amp (which in my case acts as a USB-attached sound card to the OS) to handle this in an optimal fashion (which I assume it does).
This again begs the question, how this applies to S/PDIF output, in which case the OS talks to the on-board sound card, which passes on the stream to the amp.
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Offering some thought for your project.
I currently run a setup similar to what you are asking, maybe two setups similar to what you want one I am running a digital link between the other is analog.
First from what I understand from your post is for the audio coming from your cd player or whatever source to be passed into a pc, and or you would like you audio from pc to be processed through your amp. Either way you would like a solution which is controllable through the pc.
This is how I do it maybe it could help out on your thoughts. Also I would like to add that I use a 10" windows ce touchscreen tablet ( $100 or less on ebay) to access a complete home automation website that I built which interacts with XBMC and some other cool features ( another thread ).
ANALOG:
Running on dual core pc is a 24bit sound blaster sound card. The amplifier is being controlled via rs232 and a simple html based webpage using eventghost. I run two pairs of monster cable ipod adapters 1/8" inch stereo one going into the pc sound in another coming from the pc sound out.
Via Eventghost plugins serial & webserver and a custom made integrated html page, I setup volume plus all inputs and outputs for control of the amp.
DIGITAL: Almost the same just slightly different
Running on dual core pc is a asus sound card. The amplifier is being controlled via TCPIP ethernet connection and a html based webpage using eventghost. I run two digital optical cables one going into the pc sound in another coming from the pc sound out.
Via Eventghost plugins event sender & webserver and a custom made integrated html page, I setup volume plus all inputs and outputs for control of the amp.
Both work flawlessly for me hopefully this may help with your project
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All:
Adding my two cents to this post.
You'll get the best SNR by keeping the source at full level and letting the receiver adjust its volumn levels either in its digital or analog domain.
I am also interested in some sort of scheme that would allow me to passthrough control my amplifier via RS232. So if the Kodi "receives Events" where can I find the code that intercepts and perhaps then dispatches commands based on those received events......
Peter