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MPD Audio Settings for HiRez Files


ClothEars

Question

I have been trying to understand MPD audio settings in an attempt to deal with some occasional skips when playing .WAV files from an external hard drive connected via USB to a SOtM SMS-200 Ultra.

The skips do not appear to depend on the resolution of the file.  The settings that can be adjusted through the web based interface "Eunhasu" are:

 

audio_buffer_size <size in KiB>    This specifies the size of the audio buffer in kilobytes. The default is 2048, large enough for nearly 12 seconds of CD-quality audio.

 

buffer_before_play <0-100%>    This specifies how much of the audio buffer should be filled before playing a song. Try increasing this if you hear skipping when manually changing songs. The default is 10%, a little over 1 second of CD-quality audio with the default buffer size.

 

buffer_time <time in microseconds>    This sets the length of the hardware sample buffer in microseconds. Increasing it may help to reduce or eliminate skipping on certain setups. Most users do not need to change this. The default is 500000 microseconds (0.5 seconds).

 

period_time <time in microseconds>    This sets the time between hardware sample transfers in microseconds. Increasing this can reduce CPU usage while lowering it can reduce underrun errors on bandwidth-limited devices. Some users have reported good results with this set to 50000, but not all devices support values this high. Most users do not need to change this. The default is 256000000 / sample_rate(kHz), or 5804 microseconds for CD-quality audio.

 

The default values in Eunhasu are:

audio_buffer_size:  4Mb  (4,000 KiB) 

buffer_before_play:  0%

buffer_time:  0.2sec  (200,000 microseconds)

period_time:  5msec  (5,000 microseconds)

 

To deal with 24bit/192KHz files what should be the preferred settings?  Should I just quadruple the values to accommodate Hi Rez files?

Any assistance in understanding these variables (particularly the last two) and how they interact when dealing with Hi Rez files would be appreciated.

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On 3/22/2019 at 10:48 PM, ClothEars said:

The default values in Eunhasu are:

audio_buffer_size:  4Mb  (4,000 KiB) 

buffer_before_play:  0%

buffer_time:  0.2sec  (200,000 microseconds)

period_time:  5msec  (5,000 microseconds)

 

To deal with 24bit/192KHz files what should be the preferred settings?  Should I just quadruple the values to accommodate Hi Rez files?

I don't know much of anything regarding these variables but my sms-200 MPD settings (connected via Wi-Fi and ethernet) accommodate hi-rez files up to 192/24 and 2X DSD with no dropouts or weird noises. The only difference from your values is in "buffer before play". Buffering seems like it should  be a good thing to do:

 

audio_buffer_size:  4MB

buffer_before_play:  10%

buffer_time:  0.2sec 

period_time:  5msec 

 

The sms-200 originally came with 8GB of RAM. When firmware was upgraded to V4.5, it took up more than 7GB and I started having difficulties playing files. When I inquired with May Park, she suggested an upgrade to 10GB. I went with 16GB for possible future adaptability.

 

 

Main System: QNAP TS-451+ NAS > Silent Angel Bonn N8 > Sonore opticalModule Deluxe v2 > Corning SMF with Finisar FTLF1318P3BTL SFPs > Uptone EtherREGEN > exaSound PlayPoint and e32 Mk-II DAC > Meitner MTR-101 Plus monoblocks > Bamberg S5-MTM sealed standmount speakers. 

Crown XLi 1500 powering  AV123 Rocket UFW10 stereo subwoofers

Upgraded power on all switches, renderer and DAC. 

 

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9 hours ago, audiobomber said:

I don't know much of anything regarding these variables but my sms-200 MPD settings (connected via Wi-Fi and ethernet) accommodate hi-rez files up to 192/24 and 2X DSD with no dropouts or weird noises. The only difference from your values is in "buffer before play". Buffering seems like it should  be a good thing to do:

 

audio_buffer_size:  4MB

buffer_before_play:  10%

buffer_time:  0.2sec 

period_time:  5msec 

 

The sms-200 originally came with 8GB of RAM. When firmware was upgraded to V4.5, it took up more than 7GB and I started having difficulties playing files. When I inquired with May Park, she suggested an upgrade to 10GB. I went with 16GB for possible future adaptability.

 

 

 

I too use a 10% buffer but of particular interest are the last two variables - Buffer Time and Period Time.

I would like to understand how these variables set up the data stream to the DAC and their significance.  All the literature seems to only deal with CD (16Bit/44.1KHz) data streams and I was hoping someone on this site may be able to provide some insight into these variables in layman's terms.

 

Unfortunately to date there appears to be no-one with this kind of knowledge to share.

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You have the explanation in your first post. But in general, MPD will read the data from a buffer. The buffer provides a predictable data set to work with. This happens when you stream via ethernet or access the audio via the file system, like USB. The buffer will always be faster than the audio sources as it is local to MPD (running in memory). Things to consider:

 

1. Is your external drive SSD or magnetic?

2. Do you get this issues when streaming form the net or a NAS?

3. Is your external drive powered by the SMS-200 or by an external power supply?

 

If you know the answer to these three points you should experiment around them to see if the problem goes away.

 

 

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9 hours ago, Ran said:

You have the explanation in your first post. But in general, MPD will read the data from a buffer. The buffer provides a predictable data set to work with. This happens when you stream via ethernet or access the audio via the file system, like USB. The buffer will always be faster than the audio sources as it is local to MPD (running in memory). Things to consider:

 

1. Is your external drive SSD or magnetic?

2. Do you get this issues when streaming form the net or a NAS?

3. Is your external drive powered by the SMS-200 or by an external power supply?

 

If you know the answer to these three points you should experiment around them to see if the problem goes away.

 

 

 

Thanks for your help.

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