On 2020-03-14, Yorick Hardy wrote: > Dear nia, > > On 2020-03-14, nia wrote: > > On Sat, Mar 14, 2020 at 12:20:11AM +0200, Yorick Hardy wrote: > > > You are correct. I threw together a NetBSD audio driver based on the oss > > > driver, but it had exactly the same problem. Strangely, I have been > > > unable to > > > reproduce the problem on an old i386 netbook (so far). > > > > > > I wrote a test program to try and reproduce what ffmpeg is doing, and > > > (I am not sure yet) it seems like non-blocking reads is causing the > > > distortion. The same test program with blocking reads seems to work > > > okay. > > > > > > I will look into it a bit more, and then report back. > > > > Right, /dev/audio doesn't support non-blocking I/O. But you're supposed to > > do short enough reads and writes that it shouldn't matter. That might be > > the cause of the worst of the problems. > > Oops, I think the man page might need to be updated then. > I managed to convince my test program to correctly record > with non-blocking I/O (perhaps by accident?) by working > a bit differently to ffmpeg, but I am not sure how to > adjust ffmpeg in this way. I will try blocking reads > (presumably reading blocksize bytes at a time). > > Re: audacity (earlier in the thread), audacity hangs whenever I try to > record. I probably need to update all of my packages - but I am not > doing any long builds at the moment due to unpredictable electricity > supply! > > > Do you want to work on this together somewhere? > > Yes, that would be great! As long as you don't mind someone who is > extremely unresponsive most of the week! I have quite a few deadlines > in the next week, and will probably ignore most things while I am > doing that work. > > Attached are the patches for my "testing" version of the ffmpeg > backend (heavily based on the OSS backend). I am sure it should be > renamed to "netbsd", initially I was trying for sun compatibility - > but I am not sure that makes sense.
Just a side note that I keep forgetting to mention: I used ffmpeg and oss to record videos over the last few years and "it used to work fine". I think that the most recent audio changes have broken some expectations that ffmpeg has, but it used to work (more or less) as ffmpeg expected. That said, I think a netbsd audio backend would be great. I will create a pkgsrc-wip package in the mean time to start working on a netbsd audio backend, unless someone beats me to it! [wip/ags also has some audio problems, it uses allegro for audio; but I will start another thread about that one day.] -- Kind regards, Yorick Hardy
