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Author Topic: Problem with Push + DSP + Gapless Playback  (Read 1112 times)

Groundhog

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Problem with Push + DSP + Gapless Playback
« on: January 08, 2015, 12:22:12 pm »

Configuration:
   2 PCs, both running MC 20.0.52 on Windows.
   PC1 is pushing  audio to PC2

On PC1, a DLNA server D1 is set up and the PC2 zone is associated with D1.
Options -> Media Network -> DLNA Servers -> D1 -> Audio
   Mode: Specified Output
   Format: PCM 24 Bit
   Advanced -> Sample rate: 48000 hz

PC2 Audio is set to play gaplessly.
Options -> Audio -> Track Change
   Switch tracks: Gapless
   x Do not play silence (leading and trailing)
   x Use gapless for sequential album tracks

When playing from PC1 to PC2, gapless playback is not smooth. There is an audible transition – a small but noticeable glitch - between tracks when the music is continuous across the track boundary.

The problem happens when the Sample rate is set to anything other than “Same as source.” When the sample rate is set to “Same as source,” gapless playback works smoothly.

Thinking this might be a problem with PC2, I tried another PC in the role of PC2. The same problem occurs, despite significant differences in hardware and OS version.

Could this be a configuration problem? a bug undocumented feature?

Thanks,
-Brent
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Arindelle

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Re: Problem with Push + DSP + Gapless Playback
« Reply #1 on: January 08, 2015, 02:59:35 pm »

sorry you've lost my when you say "D1" .... what are you referring to? a zone?

So you have a media server running form PC1 using PC2 as a client/renderer? If so when you say pushing do you mean that PC1 is the control and server? Or is PC2 the control?

Unless D1 is some kind of DLNA renderer, I would try the generic DLNA first .. sample rates should be the same as source from the server generally .... Switching sample rates is probably causing the "glitch" you are noticing (which might be coming from your DAC too). If you want to upsample, do that from PC2 as the renderer. (out of curiosity why choose 48K and 24bit?)

Although as I said, maybe I'm confused about "D1" and your configuration is more complex  ?

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Groundhog

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Re: Problem with Push + DSP + Gapless Playback
« Reply #2 on: January 09, 2015, 06:35:24 am »

Arindelle,

Thanks for the reply. I apologize for the confusion. I'll try to unmuddle things...

sorry you've lost my when you say "D1" .... what are you referring to? a zone?
"D1" is simply the name of a DLNA server that I set up within MC20 on PC1. The configuration of "D1" is, as mentioned, is for PCM 48/24.
(Tools -> Options -> Media Network -> Add or configure DLNA servers)

Quote
So you have a media server running form PC1 using PC2 as a client/renderer? If so when you say pushing do you mean that PC1 is the control and server? Or is PC2 the control?
PC1 is the control and media server, PC2 is the renderer.

Quote
Unless D1 is some kind of DLNA renderer, I would try the generic DLNA first .. sample rates should be the same as source from the server generally .... Switching sample rates is probably causing the "glitch" you are noticing (which might be coming from your DAC too). If you want to upsample, do that from PC2 as the renderer. (out of curiosity why choose 48K and 24bit?)
1. PC2 is connected to a a DAC which only supports resolutions up to 48/24.
2. My music library has resolutions ranging from mp3 to FLAC 192/24 to DSD64.
3. PC2 is a CAPS v3 Carbon with a JMark of about 650. It doesn't have sufficient processing power to convert DSD to PCM.
4. PC1 is much faster, JMark around 4000.

I have a higher resolution DAC preordered which *should* arrive in the next month or two. I'll configure things differently at that time. In the meantime, I thought I'd work around some of the system limitations by having PC1 resample everything to 48/24. This works very well for most material, but - as mentioned - gapless does not play smoothly.

I don't understand why there would be a glitch due to switching sample rates. PC1 is converting everything to 48/24 before pushing it to PC2. From PC2's perspective, it's playing one track after another - all at 48/24.

I did as you suggested and set the media server sample rate set to Same as source. This actually works fine for PCM, but I run into the gapless glitch when playing DSD… which is consistent, since DSD has to be converted to PCM before it can be pushed to PC2. It seems that any time DSP is engaged to resample music on the media server, the renderer has the gapless playback glitch.

I hope this is more clear.

Thanks,
-Brent
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AndrewFG

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Re: Problem with Push + DSP + Gapless Playback
« Reply #3 on: January 09, 2015, 06:53:25 am »


Doing gapless often means that for a certain period of time the MC server might be running two track serve tasks in parallel (the end of the current track plus the beginning of the next track). Such parallel server tasks are most likely to occur on shorter tracks (more track transitions) and on renderers with small buffer sizes. In particular if the server tasks involve "heavy lifting" (such as DSD transcoding and/or DSP) then your CPU may well hit a bottleneck which would cause stuttering until one of the two tasks completes..
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