Buffer Sizes

Ozone contains advanced controls to help you get the optimal performance for your setup. Since Ozone contains several modules within its 64-bit internal DSP chain, there are several places where you can control its internal buffer sizes. In general, the default values should give good performance on most systems, but there are some aspects of host applications that are not detectable by plug-ins. Read this section for instructions on how to optimize Ozone for your particular setup.

RTAS only: If you are using the RTAS version of Ozone inside Pro Tools, then the first option you should set is Ozone's "RTAS buffer size" found in the General options tab. You should set this to the same value you've set the "H/W Buffer Size" in Pro Tools, under Setups / Playback Engine. If you are experiencing high CPU usage, you should increase both the Pro Tools "H/W Buffer Size" and Ozone's "RTAS buffer size" for a significant improvement. Note that larger "RTAS buffer sizes" will introduce more latency into Ozone's output. You can also set Ozone's "RTAS buffer size" to 32 to introduce no additional latency, at the cost of higher CPU usage.

All plug-in formats: Some of Ozone's DSP modules required fixed buffers when set to certain modes. These include Ozone's Digital Equalizer, Digital Crossover and Room-modeled Reverb. You can set the buffer size for each of these modules independently using the EQ/Reverb/Crossover options tab. These buffer sizes default to reasonable values, and most users should be able to use Ozone right away without tweaking them.

If you experience unusually high CPU usage, you can try changing the Digital EQ to Analog mode, the Room-modeled reverb to Plate mode, and the Digital Crossover to Analog mode. You can also try increasing your host application's buffer size to decrease CPU usage. We understand that these solutions might not be adequate for many users, so we've also designed Ozone to be optimized for any host application setup.

If you are using Ozone at low latencies and rely heavily on these DSP modules, you will want to adjust the buffer sizes to get Ozone's CPU consumption as low as possible. At first it may seem unintuitive, but if you follow the tips here then you should be able to tweak your buffers very quickly and easily.

To get the best buffer settings for your setup, first you should have an idea of what kinds of buffers your host application is sending. You can use Ozone's Buffer Size Viewer to do this. Once you know what size buffers your host application is sending, try the following:

1) Place Ozone's equalizer in Digital mode, and bypass all modules except for the equalizer. Set the Digital EQ filter size to the size you most commonly use.

2) Set the Ozone's Digital EQ buffer size to the number that's closest to your host application buffer size.

3) Open a CPU meter. Many host applications have a CPU meter built-in, but if you're running Windows XP you can also press Ctrl+Shift+ESC and select the Performance tab. Note that CPU meters are usually somewhat inaccurate, but we're just looking for relative changes in CPU usage.

4) Open an audio file with typical settings (sampling rate, bit depth, number of channels) for your use and play it through Ozone. If you usually use Ozone in a multitrack environment then be sure to do the same here. As the audio plays, try adjusting the Digital EQ buffer size and see what effect it has on CPU consumption. Buffer sizes near the host application buffer size are a good starting point, but the best choice depends on many aspects of your system and host application which are beyond Ozone's control.

5) Once you have the best setting for the Ozone Digital EQ, try steps 1-5 for Ozone's Digital Crossover and Room-modeled Reverb. Be sure to test each DSP module in isolation to avoid complicating things more than necessary.

6) Now Ozone's CPU consumption for this setup should be optimized. If you change the way you use Ozone, for example if you move from 44.1 kHz to 96 kHz, or you move from a single-track setup to a mulitrack setup, then you may want to repeat these steps to make sure your buffer settings are still optimal.

We hope these steps help make Ozone useful in a wide variety of setups. We've gone to great lengths to optimize Ozone's 64-bit DSP without compromising sound quality. These steps should help you address those variables which are beyond our control and quite often very different for different users. For more tips about Ozone usage, check the Support section of the iZotope web site:

http://www.izotope.com/products/audio/support/ozone.html

As we learn more about how Ozone interacts with various host applications, we'll update these pages with the latest info.