Re: [LAD] [ANN] LV2 beta3

On Wed, May 09, 2007 at 02:53:33AM +0100, Steve Harris wrote: Some comments / potential problems. 1, Only integer sample rates. This should be at least a fraction of two integers. 2. Plugins are expected to have a fixed set of ports. There are cases where a plugin can only decide wich ports it will need after being instantiated. 3. Plugins may want to delegate some of the processing to threads running just below the audio thread priority, so this priority is an essential initialisation parameter. 4. There are 'audio rate' and 'control rate' ports, but no 'init time' ports. How are plugins supposed to discover initialisation parameters ? 5. If a plugin is instantiated multiple times to operate on multi-channel data it may want to share control ports within such a group, if only to optimise the (possibly complex and CPU intensive) code that maps external control values to internal data. I see no way to form such groups. 6. The only way for plugins to discover if a control port value has changed is to keep a copy and compare all values during each run(). See also (7). 7. There is no fixed audio period. Host may call run() for any number of samples. This is probably meant as a way to allow hosts to change control values at arbitrary points, but this defeats the purpose of having control rate in the first place. It's a typical 'let's be lazy' solution that does not solve the original problem except in some simple cases. Some algorithms can't be written to run efficiently - or at all - in such circumstances. Plugins should be run() with fixed block size. If plugins are to know that certain things need to happen at particular offsets into a processing period then they should be passed this info as a list of events (timestamed relative to the start of the period), and be allowed to deal with that in the most appropriate way, which may well be very different to slicing up the audio period. Some algorithms may even require that such events are presented some number of samples ahead of their due time. This of course forces the plugin to queue them internally, but in some cases that's the only way to do it. What is needed here is a generic way to pass a list of time- stamped event to a plugin via a control rate port, and then let the plugin deal with them as it sees fit. -- FA Follie! Follie! Delirio vano è questo !