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05-Mar-2015, 10:30
(This post was last modified: 05-Mar-2015, 10:31 by Rufus McDufus.)
One of the problems of software-induced jitter is the number of interrupts which can occur on a processor which is also processing/playing music. It's possible to shift the interrupts onto other processors cores - for instance the hardware interrupts from the USB device driver. It should be possible to do this for SPDIF drivers or whatever too.
Dedicating cores to the music-only processes also helps in theory (less soft interrupts and cpu contention).
I'm guessing many dedicated transports/players do this kind of thing already. Many are based on small computing devices like the Cubox etc.
It's best to dedicate a computer transport to music only if you're looking for out-and-out sound quality - the less going on on the box the better, but there's no reason why you can't run XBMC. I think there is a Cubox XBMC image already (not sure about Hummingboard). It might be a case if having one OS on a card with XBMC and one with Volumio or another mpd-based distro. Bit of a faff changing cards and booting the desired OS all the time though!
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Hello Rufus,
I am a newbie with Linux and multi-thread management. Some say that MPD is only mono core.
So i am very interested in any software advises to optimise sound renderer.
there is a thread for installing XBMC + Volumio on same card: https://volumio.org/forum/volumio-xbmc-a...-t609.html
I don't know the concerns for audio quality impact.
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Just had a quick look. mpd is multi-threading by the looks of it. I have all the threads (taskset on the parent proc does this) bound to 1 core on the cpu. It might well be mono core. Not sure.
It's probably possible to bind XBMC to different cores to mpd. It's probably easiest to try and install if first on (say) a Volumio install and see how it sounds and then start to make incremental improvements if desired. It'[s a bit daunting otherwise!
I was a newbie to this processor affinity/scheduling etc. stuff! It's good to learn though.
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(05-Mar-2015, 09:52)fabien44 Wrote: Hello Kunter,
your system is very powerful. I don't target yours because of lack of money but i will try to customise best as possible.
A friend will build specific power linear supply to deliver 2x5V/2A to feed SSD and hummingboard.
He is also working on specific box to welcome everything (SSD, Hummingboard, EMI shields, heat dissipation, ...). The hummingboard cpu temp can be very high, so the box should be designed to evacuate heat.
You compare to Aries but wich one, the LE or femto/LPSU one?
What do you mean about cores isolation? I read in your previous posts that you dedicated 2 cores for MPD and 2 cores for USB, why USB? I will not use USB, just mSata and SPDIF coax.
But i would like to install XBMC upon on Volumio to be able to watch movies. What do you think about? I read in solid-run forum, someone who did that.
Have a nice day
Fabien
I compared Aries with Femto/LPSU...
Since I do not use this device for anything but music, I cannot comment on the XBMC issue, but Rufus covered the topic quite well...
Playing around with software optimisations, it is just funny how this little device improves on performance.
MPD has 4 threads while running.
Player, Decoder, Output and one other.
I dedicate 2 cpu's to MPD, increase their priority to Realtime, and they chose which of the 2 cpu's they run on.
Sound is great.
Cheers.
Kii Three, dCS Network Bridge, Roon Nucleus, Kuzma (Stabi S, 4Point), Soundsmith StrainGauge, Stromtank, Echole Cables
Istanbul, Turkey
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25-Mar-2015, 17:05
(This post was last modified: 25-Mar-2015, 17:12 by fabien44.)
(05-Mar-2015, 18:52)Kunter Wrote: MPD has 4 threads while running.
Player, Decoder, Output and one other.
I dedicate 2 cpu's to MPD, increase their priority to Realtime, and they chose which of the 2 cpu's they run on.
Sound is great.
Cheers.
Hello Kunter,
how did you set cpu tasks and priority? I guess in a volumio settings file, but which one?
Same for memory cache before playback. How did you do that?
Thanks
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taskset -pca 2,3 $(pidof mpd)
chrt -pfa 99 $(pidof mpd)
either run these everytime from shell
or create a shell script and run it everytime system boots
or put these lines directly in /etc/rc.local
for buffer settings, I edited the relevant lines in the /var/www/mpd-config.php
looks like this
// buffer_before_play
$_mpd_select['buffer_before_play'] .= "<option value=\"0%\" ".(($_mpd['buffer_before_play'] == '0%') ? "selected" : "")." >disabled</option>\n";
$_mpd_select['buffer_before_play'] .= "<option value=\"10%\" ".(($_mpd['buffer_before_play'] == '10%') ? "selected" : "")." >10%</option>\n";
$_mpd_select['buffer_before_play'] .= "<option value=\"20%\" ".(($_mpd['buffer_before_play'] == '20%') ? "selected" : "")." >20%</option>\n";
$_mpd_select['buffer_before_play'] .= "<option value=\"100%\" ".(($_mpd['buffer_before_play'] == '100%') ? "selected" : "")." >100%</option>\n";
and use the web interface to select 100%
Kii Three, dCS Network Bridge, Roon Nucleus, Kuzma (Stabi S, 4Point), Soundsmith StrainGauge, Stromtank, Echole Cables
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29-Mar-2015, 09:44
(This post was last modified: 29-Mar-2015, 09:50 by fabien44.)
Hello Kunter
thanks for the infos.
I received my hummingboard i4 pro carrier, i install Volumio and i can say it sounds very good, different from my Aries but not worse. I would say the sound with Aries is thinner but maybe more coherent, the HB seems to focus medium in front, to be confirmed.
I just power it with the stock power unit but I am building a aluminium box based on the following couple boxes:
http://www.ebay.fr/itm/202x80x282-Alumin...5d4d0eda69
http://www.lincolnbinns.com/raspberry-pi...-enclosur/
Which will welcome the hummingboard + HDD 2.5 spinning + DIY linear power supplier 2x5V 2A to power the whole system.
(SSD costs too much at the moment and i don't think the gap in SQ justifies the extra cost).
I did some test with another contribution: KODI, which is a mediacenter software. I like it to watch movies and ripped DVD of music concerts.
You should try this one, after 1 hour of listening i couldn't hear any difference with Volumio. It's more user friendly and more stable to me.
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I have a Raspberry Pi 2 with Volumio installed on it. Do you know if the same optimization can be done on the Raspberry Pi as on the Cubox?
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Ok so I managed to add the 100% buffer to the buffer settings. What do you use for audio buffer size? The default is 2048, which seems too small. How large should I go? Also what are you using for a control point? I tried Lightning DS but it didn't want toward for me. The Lumin app seems to work well.
BTW I'm really liking the sound of this. I'm powering the Raspberry Pi 2 with a Mophie power battery pack. I'm using an Audioquest Diamond USB cable into an if iUSB power supply to an if Gemini dual head USB cable to the 200.
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Another update. I installed Logitech Media Server and Ickstream on my Synology NAS, installed Squeezelite on the Raspberry Pi, and iPeng 8 on my iPad.
I can now stream Tidal to the 200 from my iPad using iPeng. I only tried it for a moment but it sounds good and is very easy to use. When I switch back to the the Lumin app the Raspberry Pi uses MPD again.
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