AAX block size


I am having problems with my JUCE AAX plugin (OSX) - no matter what, blockSize() always returns 1024, regardless of audio buffer size value in Pro Tools. I believe 1024 is the default value when JUCE AAX wrapper is instantiated. I am checking before processing data, in prepareToPlay() and in several other places - it is always 1024.

I don't have problems with VST in Reaper for example, i always get correct blockSize value.

Any ideas ?




I've no idea how PT handles the relationship between the user-selected buffer size and the size of buffer that it uses to render plugins, but it's not necessarily the same number.

You can see in the juce AAX wrapper code that PT directly passes in the number of samples it wants, and that gets strored in the value returned by getBlockSize(). There's no room for a bug there - if the number was different to the size that PT expects, then your plugin would instantly crash or produce garbled audio.


I have a plugin here, which depends on a host's buffer size to switch to zero-latency mode.  Is there any other way to query host for user selectable buffer size - i mean general approach, regardless of host ?


No.. Can't really see how the buffer size would be relevant to that though, its size tells you very little about what the user is doing.

Surely better to make such a mode a parameter, or to do it based on whether the plugin is currently off-line rendering?


But how could PT use low latency HW buffer size, if forces plugins to process 1024 frame buffers ?

I have a feeling that you are talking about "off line rendering" - i am talking about real time processing ...

Am i missing something ?






OK, i've found out - when track is record enabled, PT actually changes buffer size to actual HW buffer size value. 

This was a bit tricky to find out, but now things work as expected ...

Thx for help and brain storming !!!