DSP status

Does the DSP status in the upper right of the editor window indicate the work being done by the sound card’s processor? The reason I ask is I also have gnome-system-monitor running, which shows my CPU operating near its limit and sometimes maxing out, while the DSP status is only about 65%. How can I tell if my sound card is using its full processing potential? I’d like to pass as much of the DSP workload to the card as possible.

I have a Roland RPC-1 card, which evidently uses the ICE1712 chip. It’s capable of simultaneous 8 inputs/8 outputs of up to 96kHz, 24-bit audio. I’ve installed the linux-rt kernel; added myself to the audio group; set the rtprio, nice, and memlock variables; and set JACK to Realtime with 256 Frames/Period and 2 Periods/Buffer running at 48kHz. This gives me a latency of 10.7ms, which is not terrible but I’m an audio zealot I want to tweak it some more. Operating a session at 96kHz produces lots of xruns, even with the Frames/Period set to 1024.

Also, window redrawing is kind of slow (i.e. scrolling, switching between the editor and mixer, etc.). I have an NVIDIA GeForce FX 5500 with the nvidia-glx-new driver working correctly, FastWrites and Side Bus Addressing turned on, and all fancy compositing eye candy turned off. Any tips on tweaking the graphics card further? I’m just trying to think of everything that can be done without overclocking any processors.

The number shows what percentage of the available time for processing audio is being utilized by JACK and all its clients. If you are running at 1024 frames/period and a 48kHz sample rate, there are 21msec between interrupts. If all audio processing (per period) is complete in (an average) 10msec, you would see that number say about 50%.

We have found that in practice, on both linux + OS X, this number can’t go over about 80% without problems.

I can’t comment on your graphics issues. I use a similar card/device in my laptop, and I can’t say it strikes me as slow, but opinions may vary. Note however that a 65% DSP load is very high. It would likely impact graphics performance in the CPU (not the graphics card) by stealing cycles from the X server and Ardour’s GUI thread.

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Workstation is faster now… see here for details.