On the topic of multithreading: I'm currently experiencing total
composition block when loading a new video file (via the "movie
importer" patch).
This is quite ugly for the kind of live performance I'm doing ... I've
tried being semi-clever about it and render the next set of movies onto
hidden sprites, but I'm only shifting the blockage around. At some point
in time it *does* happen.
Is there anything I can do
- with the builtin set of patches
- with some 3rd party movie player I'm not aware of?
(If necessary I'd be willing to converty my footage to anything ffmpeg
and friends can spit out)
Cheers,
Anatol
On 17.5.11 8:27 PM, Christopher Wright wrote:
I would like to move from a polling (CVDisplayLink) to a event driven rendering
model in my app. I would like to use GCD and named dispatch queues, but I am
concerned about QA 1538 (Multithreaded QCRenderer) :
http://developer.apple.com/library/mac/#qa/qa1538/_index.html
Specifically, if I have a named dispatch queue, and alloc/init, and render
content in this queue only, is that safe and guideline following? My
understanding is, a queue can bounce around various thread pools, and wont,
technically, be on the same literal thread. Thus my question.
What say ye? Yay or Nay?
This will be a problem under the current implementation - internally some
resources are tied to pthreads (via pthread_set_specific), and that doesn't
work so well under GCD, where, as you say, queues can migrate threads.
One thing you could do is set up a thread for the renderer that waits on a
dispatch_semaphore, and then in the GCD block signal the semaphore when you
want it to render. This will add some latency, but it'll remove the polling
model without violating the thread guarantees QC currently expects.
--
Christopher Wright
[email protected]
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