| |||||||||||||
BSDBSDPosted Jul 6, 2011 11:02 UTC (Wed) by tialaramex (subscriber, #21167)In reply to: Interview with Lennart Poettering (LinuxFR.org) by trasz Parent article: Interview with Lennart Poettering (LinuxFR.org)
The "transparency" you're proclaiming in FreeBSD OSS is achieved by running this tricky CPU-intensive code in Ring 0 even though it doesn't need any special privileges. This is the Wrong Thing™ so it's prohibited in Linux.
V4L went through this same thing, but sanity prevailed, and today programs use a userspace library to do any conversions or tweaks needed to get data they can understand from cameras which may natively emit a variety of unusual image formats. Do the BSDs still have thousands of lines of buggy YUV to RGB conversion code in their kernels in order that you don't need such a library to read RGB data from a YUV webcam?
(Log in to post comments)
BSD Posted Jul 6, 2011 11:09 UTC (Wed) by trasz (guest, #45786) [Link]
It's not that CPU-intensive. On a typical hardware I doubt it's even measurable. And the kernel is preemptible, so it wouldn't matter much anyway. And, if you don't like it, you can disable it. Point is, functionally, there are very few things ALSA does better than OSS, despite lots of added complexity.
I have no idea how the situation looks like with V4L, or any video, for that regard.
BSD Posted Jul 6, 2011 14:45 UTC (Wed) by bronson (subscriber, #4806) [Link]
256 point sync is barely measurable?? Wow, what hardware do you have?
Preemption contributes to latency. That's usually a problem, not a solution.
BSD Posted Jul 6, 2011 14:49 UTC (Wed) by bronson (subscriber, #4806) [Link]
I don't mean to ignite a preemption discussion. My point is only that "just fix it with preemption" is oversimplified and probably won't work.
BSD Posted Jul 6, 2011 18:25 UTC (Wed) by trasz (guest, #45786) [Link]
Could you explain what's the "256 point sync" and how is it related to the preemptiveness of the kernel?
BSD Posted Jul 6, 2011 20:49 UTC (Wed) by bronson (subscriber, #4806) [Link]
oops, I meant sinc of course. Finger habits. Decent quality sinc takes a good chunk of your CPU.
The bit about preemption is a reply to your statement:
> And the kernel is preemptible, so it wouldn't matter much anyway
|
|||||||||||||