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Old 15th January 2013, 03:44 PM   #2071
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Glad to hear it, nikkov!

As mentioned above, mpd will use the Broadcom audio device by default. The audio-widget readme file says how to configure mpd to use your USB audio interface. Basically it is like 1audio says above.

After some more listening, I've noticed occasional glitches (once per few minutes) when the USB keyboard is connected, even without touching any keys. I did some listening this morning with the keyboard disconnected, so all of the USB devices in the system were 2.0. I didn't hear any glitches.
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Old 15th January 2013, 03:46 PM   #2072
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people do report problems with keyboards. very odd, but with a headless player, its easy to work-around.

since its networked, once its booted and online, there is no need to have a keyboard attached. the only times I have a keybd on is when I'm doing the initial install. and then, you need hdmi out, too.
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Old 15th January 2013, 04:46 PM   #2073
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people do report problems with keyboards. very odd, but with a headless player, its easy to work-around.

since its networked, once its booted and online, there is no need to have a keyboard attached. the only times I have a keybd on is when I'm doing the initial install. and then, you need hdmi out, too.
My ARM based Linux MPD player systems have never had a keyboard or a display connected.
File system built with debootstrap on a Intel Linux system, and kernel compiled without display support to have the full 1GB or 2GB RAM available to MPD.
Kernel is compiled without modules as everything needed are compiled into the kernel. ALSA source code are modified to optimize the USB transfers and reduce the IRQs from the normally 2000 pr. Second down to ca. 100...
USB adapter are now running with 32 milli second feedback timing (not the standard 1ms).
SSH are used to control the Linux systems either from iPad or MacBook Pro.
USB 2.0 and SATA RAID are galvanic isolated.
SATA RAID / SATA SSD are used due to DMA, speed and lower system resource usage as the NAS connection uses to much CPU and creates to much IRQs.

MPD is configured with onboard I2S and two USB adapters.
One or two or all three are selected / deselected from the MPD control client, MPoD, MPad or MPC.
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Old 15th January 2013, 05:06 PM   #2074
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Originally Posted by RayCtech View Post
SSH are used to control the Linux systems
Ahh that sounds like beautiful music. I ssh to Lynx to play files through aplay. It is very primitive. Now I'm becoming interested in the Rasberry PI approach. Maybe just add an LCD and a few buttons or IR sensor for IO.
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Old 15th January 2013, 05:42 PM   #2075
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RayCtech, this sounds very interesting Is there any way we could apply your modified source code to the Pi/Audio-Widget system?

Also, if you have been in the ALSA source, maybe you can shed some light on this:

When experimenting with my previous DAC, I found that I got glitches using the "hw" interface, but changing to "plughw" got rid of them, even though the plug module was supposed to be just passing the data through with no resampling or bit depth conversion.

So, does ALSA's "plug" module buffer more data somewhere in the kernel, where it could respond with a lower interrupt latency? Does it follow that using it on my current setup might help with the keyboard glitches?

I'm confident that plug won't resample or twiddle bits unless there is a genuine need for it, as I've verified bit-perfectness with it in the signal chain.
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Old 15th January 2013, 05:43 PM   #2076
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Ahh that sounds like beautiful music. I ssh to Lynx to play files through aplay. It is very primitive. Now I'm becoming interested in the Rasberry PI approach. Maybe just add an LCD and a few buttons or IR sensor for IO.
SSH for Linux, MPaD or MPoD or similar for MPD control when playing...
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Old 15th January 2013, 06:51 PM   #2077
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using an android phone (for example) you can control the playlist, shuttle and volume of mpd systems.

I used a cheap $100 nook color tablet and put cyanogen mod on it (trivially easy and reversable) and that sits literally ON my stereo shelf and gives a graphical (album art, too) display. touch screen for volume and even swipe left/right to skip back/forward. with that config, I have not found the -need- to have an attached lcd display (and I happen to love the 16x2 hitachi style 'easy' lcd displays).

tablets are getting so cheap, you can have one sit on your stereo shelf, one near the coffee table, etc etc. they all use wifi and all sync with each other (move the vol slider on one and the others update). pick it up from the stereo shelf, carry it to another room, use it there. freedom!
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Old 15th January 2013, 06:54 PM   #2078
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btw, there is a rpi thread on diyaudio, and perhaps we should move the platform-specific discusion over there, to keep this channel clear and more on-topic:

Raspberry Pi -A New DIY'ers Digital Hub?
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Old 15th January 2013, 06:59 PM   #2079
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Is there any way we could apply your modified source code to the Pi/Audio-Widget system?
I tested also the Qnktc and WaveIO and I do not remember the numbers for the separate adapters clearly, but I think I was able to reduce the IRQs from 2000 pr. second down to 1400 (maybe it was 1200).

The inbound IRQs (1000) are caused by the feedback setting in the adapter. The outbound I then reduced from 1000 to 400 or 200.

With the Amanero adapter I got down to a total of 140 IRQs pr. second as a total of inbound and outbound. 125 due to the feedback and ca. 15 due to data..

Now with my custom adapter that is based on a Amanero chipset I have reduced to the 50 area...

But the internal I2S (ARM CPU) uses DMA effectively and are down to 10 IRQs pr. second with a 3.5 ps jitter / 0 ppm clock - SPDIF output at +- 30 ppm.

Last edited by RayCtech; 15th January 2013 at 07:03 PM.
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Old 15th January 2013, 07:12 PM   #2080
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Maybe a better question is: Where can I get this ARM board that has an ALSA driver for the onboard I2S peripheral? it would replace both the Pi and the USB-I2S.

I'll write about my Pi project in the other thread mentioned above when it's complete. I built a user interface based on a $16 backup camera monitor, an Arduino with an encoder and some buttons attached, and ncmpc (the console client for mpd) but I also like to use the Mpod client on my phone. Maybe I'll leave the UI out in the end.
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