Increasing OpenMPT's performance on low-end computers

[LPChip]

I have a state-of-the-art computer in my livingroom, and I have a piece of crap in my bedroom.

Occasionally, I like to lay down on my bed and listen to some music. As my newer music is VSTi intense, I notice that I can't really play those songs on my pc. I have an external Creative Soundblaster 5.1 attached, which does the sound processing for me. For that reason, I can have the latency low enough, but I fail in cpu power.

I did some experimenting with the audio settings, and I found a few things out that might help you playing the more cpu intensive songs!

speakerOutput
By default sound will be set to Quad 32-bit. Setting the bitdepth won't change the performance in a noticable way. (atleast not that I noticed). Changing Quad to stereo did increased performance. Doing so is not a significant boost, but might be that little edge you need.

Resampling frequency
By default, the resampling frequency is set to 44.100 hz. When I lowered this to 20.000 hz, I noticed a big performance boost. It will mean that the sound quality is not that good. Higher frequencies will become a bit muddier, but it will certainly help. If you can't select this, then switch to DirectX. ASIO might block you from selecting this. I got an even bigger boost when I set it to the lowest setting: 16.000 hz, but I found the small gain in comparison to the sound quality loss enough to go for 20.000hz.

I could play almost any song with 20.000 hz that has VSTi's and VST effects on it. True, the more heavy the song is, the less it will perform, but it will be better than expected, thats one thing I'm sure about.

secondary buffers
There's a checkbox to use secondary buffers. I have a feeling this setting's performance will vary from system to system, but its something you can check. If your buffers perform well and you don't need the secondary buffers, disabling this can give you a small performance boost.


A few years ago, I've started the MODPlug Tracker Competition. I created the song Triangular Noise, and I heard complains from people that it didn't run properly. When I played this song on my low-end pc, I had the same problem. Lots of stutter and slowness, it just wasn't cool to listen to the song.

I only changed the playback frequency to 20.000 hz, and the song plays without any stutter what so ever!

If you are on a low-end pc, I'd like to hear your findings based on this post.

[Saga Musix]

Setting the bitdepth won't change the performance in a noticable way. (atleast not that I noticed).

True. MPT's internal mixing precision is always 32-Bit, and reducing the bit depth does just add additional conversion steps (though they are also performed at 32-Bit because ASIO soundcards normally want 32-Bit float and not 32-Bit integer audio, so it's the same math done in both cases).

Changing Quad to stereo did increased performance. Doing so is not a significant boost, but might be that little edge you need.

Obviously mixing 4 channels takes more time than mixing 2 channels, so it does make a big difference. Note that VST mixing is currently always done in stereo, even with multichannel plugins.

By default, the resampling frequency is set to 44.100 hz. When I lowered this to 20.000 hz, I noticed a big performance boost.

Note that not all plugins are compatible with playback frequencies this low.

There's a checkbox to use secondary buffers. I have a feeling this setting's performance will vary from system to system, but its something you can check. If your buffers perform well and you don't need the secondary buffers, disabling this can give you a small performance boost.

"Secondary buffers" means that MPT doesn't have exclusive access to the DirectX driver. It should actually increase performance, if anything - but not on MPT's side, but rather in the driver.

Some more obvious settings to decrease CPU load are the number of mix channels (especially with tracks that use many VSTis a low number won't do any harm, since this is just sample voices) and disabling any of the internal DSPs like EQ, Reverb or XBass and of course the interpolation mode does also matter - no interpolation does only take slightly less CPU time than linear interpolation, though.

[Saga Musix]

Oh and you will also get a theoretical and probably very small boost from choosing a sample rate that is a multiple of 11025Hz or 12000Hz, depending on what the C5freq for most of your samples is - f.e. if your playback rate is 44KHz and all your drum samples are sampled at 44Khz, no resampling is applied.

[Harbinger]

Excellent and interesting info which needs to supplement the relevant sections in the OHM. Thanks!

[LPChip]

Excellent and interesting info which needs to supplement the relevant sections in the OHM. Thanks!

May I add, that I would suggest upgrading hardware over adjusting these settings when it comes to composing. If you just want to playback, this is an excellent way to lower the computer specs.