06.11.2014 15:50, Alexander E. Patrakov wrote: > 06.11.2014 15:39, David Henningsson wrote: >> >> >> On 2014-09-30 15:59, Alexander E. Patrakov wrote: >>> 30.09.2014 19:07, David Henningsson wrote: >>>> >>>> >>>> On 2014-09-26 14:17, Tanu Kaskinen wrote: >>>>> A summary of my proposal: >>>>> >>>>> To add LFE low-pass filtering, just hack the current remixer >>>>> implementation, no need for interface changes anywhere. >>>> >>>> Actually, I think this could be good enough, at least as a first step. >>>> >>>> Do you think it would be okay to: >>>> >>>> - Implement a LR2 or LR4 filter by "hacking the current remixer >>>> implementation" >>> >>> For me, it would be okay, but I would prefer a slightly more complex >>> plan, purely to avoid the blame of the form "you demand fully >>> rewindable >>> code everywhere from others but just wrote an LFE-remixer that doesn't >>> handle rewinds correctly". The plan is: >>> >>> 1. Implement functions to calculate the coefficients of the required >>> IIR >>> filters for LR2 and/or LR4. >>> >>> 2. Implement, in a separate file, some set of functions that would >>> allow >>> one to apply an arbitrary matrix of IIR filters on a memblockq. Make >>> sure they are fully rewindable (that's the PR part), write a test. >>> >>> 3. Connect functions from (2) to the existing remixer >>> implementation. If >>> it turns out that it is impossible to form the rewind requests >>> correctly, write a TODO item. >>> >>> (2), except the test, already sits on my laptop since the previous year >>> in the form of a virtual sink. I just need to refactor it from the >>> "parallel biquads" to the "chain of biquads" form (because both LR2 and >>> LR4 have pairs of identical poles which are inexpressible in the >>> parallel-biquads formulation) and remove the sink code. >> >> Reviving this thread due to renewed interest from management. In short, >> we should probably go ahead and write this filter. I can certainly try >> to do it, but I assume you will just complain about me breaking the >> math. :-) > > That's OK. > >> Did you end up doing anything more with your existing code? Need a hand >> anywhere? > > No. In fact, I have not looked at PulseAudio code (except Peter's > patches) since the conference, and I don't have enough free time. The > earliest date when I can continue is this Sunday. > I am sorry, I could not find enough time today either. So, please go without me. -- Alexander E. Patrakov
