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[Franky]

When I use MADVR with DSP convolution, 720P movies stutter. When I switch off convolution all movies work fine.
When I use a very small tap filter length it works just fine again. But with normal size filters it does not work.
The strange thing is that all 1080p and 2160p movies are ok with long tap convolution and madvr.
I do not understand it and want it fixed. I don't think it's hardware related because I have a high end PC and GPU.

[Hendrik]

Too long filters can throw off the audio/video sync, and you get stuttering. This is a fundamental conflict and can't really be solved very easily.

[Franky]

Yet, I find it very hard to understand that with 1080p I can use extremely long filters without a problem, and with 720p I must use very small filters for JRiver to work properly.
This makes no sense to me. This problem disturbs me a lot.
I hope someone can help me out...

[mattkhan]

Are you upscaling to 4k? What is the source FPS?

[Franky]

Yes, I'm upscaling to 4k (attachment)
When I increase the lip sync offsett in JRiver to high values, > 300 ms, the problem is solved, but my lip sync is off then.

[Franky]

I must correct my post: The AUDIO is stuttering, NOT the video.
A as you can see in the jpg the MADVR is fine, but the audio is stuttering. My DAC gets interruptus in data stream.
With large lip sync and 1080p and higher all is fine.

[mattkhan]

what does cpu load look like during this?

[eve]

I'm pretty sure this trips up most people with MadVR.
If you're trying to upscale content that's LOWER resolution, it's actually *more* of a load on the system.

Say we're targeting a 4K display, and we have 4K retail video sources, well if you aren't using doubling or quadrupling, MadVR is mostly being loaded with the Chroma scaling step.
Whereas, if we're bringing up say 576p (aka SD video like you're using here, not 720p which is more in the ballpark of 1280x720) to a 4K display, MadVR is now handling some pretty intensive Luma scaling in addition to the Chroma.

Convolution filters by their nature, also have quite a significant processing demand.

A piece of advice here that might address your issues, create another MadVR scaling profile. Be a little more conservative with your settings and any doubling / quadrupling, you can apply this profile to sub 1080p content or just switch to it on the fly. See if that helps at all, yes the scaling quality might not be as good but at least it's a starting point.

Hardware specs just out of curiosity? Been toying with the idea of Convolution filters for a test bed system that doesn't handle video but I know if I like what happens I'll want it in my actual system which does demand video.

[mattkhan]

madvr will stress the GPU
convolution will put load on the CPU though any decent spec PC can handle significant convolution load without that much difficulty

one possibility is that something about the 720p processing is being done on the CPU (but is done by the GPU for higher res) and the combination is too much

anyway I'd look at cpu load next to see what it reports

[eve]

madvr will stress the GPU
convolution will put load on the CPU though any decent spec PC can handle significant convolution load without that much difficulty

one possibility is that something about the 720p processing is being done on the CPU (but is done by the GPU for higher res) and the combination is too much

anyway I'd look at cpu load next to see what it reports

There's absolutely stuff done on CPU in MadVR, it's limited but it's there. If you're loading the CPU with time sensitive convolution filters and simultaneously, madVR needs it (even if it's 'small') , you can have a latency issue.

[mattkhan]

Scaling is on the GPU which is where the additional stress should be for switching to 720p. Decoding might move to the CPU depending on the system and setup. What source of load are you thinking of that would be contingent on resolution/source?

The OP needs to give more detail on load on the system in different conditions to comment further really

[Franky]

Thanks for your replies.
I have a MSI RTX 3060 Ti 8GB and a Kaby Lake I5 7600 3.5GHz cpu with 4 cores.
The cpu load is about 42% with the individual core load attached. No CPU problem I think.

When I switch all scaling to Bilinear, audio stutter remains. And Madvr stats show very easy load (attached). CPU load about 20%.
The audio stutter stops when I deactivate convolution and the cpu load is 18%.

[mattkhan]

2 cores are rather heavily loaded

Why are you using a large decoder queue?
What settings do you have for your audio buffers in MC?

I would experiment with those settings to see if it helps, e.g. reduce the decoder queue size first then look at bumping up the audio buffers

[Franky]

When I use a small queue and play with all audio buffers
- play from memory
- prebuffer size
- Wasapi hardware buffer
- live latency
I have tried all kind of variations in buffer settings, but nothing works.
Only when I switch of convolution erverything is fine again.
Even with simple bilinear scaling and very low cpu loading the audio stutters. I don't understand it. Feels like a bug to me.