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Author Topic: Noise when switching track with convolution enabled  (Read 1336 times)

Trumpetguy

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Noise when switching track with convolution enabled
« on: April 14, 2014, 01:43:21 am »

I use 131k taps convolution filters, both for stereo and multichannel (15 paths) playback.

When starting playback of a new track, a always hear a short (but quite noticeable) noise. This does not happen when MC ends one song and starts the next by itself, only when I double click a new track. I guess its not actual noise, just a very short fragment of music. Now, I do not know the technical inner workings of MC's convolution engine, but to me it sounds like a fragment of the previous track.

Is there a way to avoid this?
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mwillems

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Re: Noise when switching track with convolution enabled
« Reply #1 on: April 14, 2014, 08:09:05 am »

I've noticed a little blast of noise when changing albums with convolution lately (the last few weeks), but only when changing between material with two different sample rates.  Does your issue occur when changing between two albums with the same sample rate?

Also, one thing to check is to make sure that convolution isn't processing independent of internal volume; i.e. make sure that "process independently of internal volume" is deselected for convolution.  I enabled it once and had really wacky results with convolution (involving snippets of music playing when they shouldn't be) until Matt helped me figure out what I'd done wrong.
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Trumpetguy

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Re:
« Reply #2 on: April 14, 2014, 03:17:14 pm »

I resample everything to 96kHz for convenience, my dac doesn't auto-switch in the preferred mode.

I will check the processing when home next week, but I don't _think_ it is selected.
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mwillems

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Re:
« Reply #3 on: April 14, 2014, 03:20:19 pm »

I resample everything to 96kHz for convenience, my dac doesn't auto-switch in the preferred mode.

I will check the processing when home next week, but I don't _think_ it is selected.

Interestingly, I also resample everything to a single sample rate, which is why I was surprised that I got a noise when playing back material with different starting sample rates.  I wonder if there's some unpleasant interaction between the resampler and the convolver?  I'll try some tests tonight and see if I can't turn up more info.
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notred

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Re: Noise when switching track with convolution enabled
« Reply #4 on: April 14, 2014, 11:55:21 pm »

Same for me...re sample, small noise when reading a file..I thought it was a sound card issue but reading your post...
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Trumpetguy

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Re:
« Reply #5 on: April 15, 2014, 05:11:42 am »

Hmmmm...maybe it is the resampler? Annoyingly enough, it will take a week before I can make any tests. But why would it then make this noise when switching between two albums with the same sample rate?
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mwillems

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Re:
« Reply #6 on: April 15, 2014, 07:47:24 am »

Hmmmm...maybe it is the resampler? Annoyingly enough, it will take a week before I can make any tests. But why would it then make this noise when switching between two albums with the same sample rate?

For me it doesn't seem to make noise when switching between two albums with the same sample rate (but see below, I forgot to test one possibility).  To be perfectly clear about what's happening on my end:

Resampler in output format set to resample everything to 44.1 (except 44.1, which is set to "no change"), convolution enabled with 44.1KHz filter (about 10k taps, if it matters).  I got the following results last night:

Convolution and resampling on:

Play movie with source sampling rate 48KHz, then play music with source sampling rate 44.1KHz; result: slight pop at start of playback.
Play album with 44.1KHz source sampling rate, then play a second album with source sampling rate 44.1; result: no pop.

Resampling off, Convolution on:

No pops with any scenario, but 48Khz material fails to playback (playback appears to start and progress, but no sound comes out).  That's probably to be expected as my convolution filter was made for 44.1 (although I keep reading that JRiver is supposed to auto resample convolution filters, but it never has for me)

Convolution off, Resampling on:

Could not reproduce pops.

So it looks like (in my case) it's an interaction between the resampler and the convolver.  I've gotten slightly weird results when combining resampling and convolution in the past too. It may not pop in between albums for me because technically the resampler isn't doing anything on my 44.1 files (which 99.5% of my collection is).  I didn't think to test whether stopping playback in between would change anything, or whether switching between two 48KHz albums would still pop.

Trumpetguy, you said you resample everything to 96KHz?  So I assume you have output format set to "do nothing" for 96KHz files?  Try switching between two 96KHz albums and see if it still pops.  If so, we may have a different problem, if not, we're getting closer to something reproducible.

Also (not that I think it should matter), but what software do you use to create your convolution filters? I use RePhase.
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Trumpetguy

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Re:
« Reply #7 on: April 15, 2014, 09:41:49 am »

Interesting test, I will follow up after Easter.
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