Date: Wed, 9 Apr 2025 16:40:30 +0200 From: Christos Margiolis <christos@freebsd.org> To: Jakob Alvermark <jakob@alvermark.net> Cc: freebsd-multimedia@freebsd.org Subject: Re: [Call for testing] sound: Implement /dev/dsp as a router device Message-ID: <srnutzvvrytv2o4e22jwvppjm7qhameth7oef5qpkil4wcm57f@3s3tbpyyz76a> In-Reply-To: <7f21cd55-5bb7-470f-88ae-c259710460bb@alvermark.net> References: <l2cfedicapbvj374ayetumvgwef5tyxwqy6kj6bapaprzkkxvt@edzltnq3km3a> <cac21f1c-997d-484d-8609-ed3d5ec2d8f4@alvermark.net> <uebrosibqnq5qbw7htd7grudl47cztc5va5dj7mitx537uv2eb@tx74cmc2y7xw> <7f21cd55-5bb7-470f-88ae-c259710460bb@alvermark.net>
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Jakob Alvermark wrote: > On 2025-04-08 00:23, Christos Margiolis wrote: > > Hello Jakob, > > > > Jakob Alvermark wrote: > > > Hi, > > > > > > > > > This is cool. > > > > > > I did some quick testing. > > > > > > Playing some audio and plugging in my USB-C headset the audio switches over > > > to the headset and continues playing in the headset. > > > > > > However, unplugging the headset does not seem to work fully. If I play > > > something in chromium (a Youtube video for example), it stops. > > See what I write below, it could be a similar issue. Also, does this > > happen on other browsers, say, firefox? > > Interestingly, with firefox, the audio does not switch over to the headset. > > I tried this: > > - Start playing audio in firefox and start playing some audio in chromium. > > - Plug in USB-C headphones. > > - The audio from firefox still plays through the laptop speaker, but the > chromium audio switches over to the headphones. > > - Unplug headphones. > > - Firefox audio still plays through laptop speakers as if nothing happened, > chromium audio stops. We can test a few things: - Can you share your /dev/sndstat with hw.snd.verbose=2 when you encounter the errors you mentioned? - Do you get the expected result if you do _not_ (un)plug anything during IO, but instead just switch between devices with "mixer -d pcmX", where X is the device's number? Also it's important to note that plugging a new device does not mean sound(4) will automatically switch to it. It also doesn't mean that unplugging a device will necessarily switch to the device you want. The driver does include a heuristic for choosing the default device, though. > > > > I tried playing an mp3 file using audio/mpg123, and when unplugging the > > > headset I get this error: > > > > > > [src/libout123/libout123.c:out123_play():746] error: Error in writing audio, > > > wrote only -1 of 2304 (Invalid argument?)! > > > main: [src/mpg123.c:play_frame():857] error: Deep trouble! Cannot flush to > > > my output anymore! > > I am not familiar with audio/mpg123, but the error message suggests that > > the program exits upon a write() error. That is not really an issue of > > sound(4), but that audio/mpg123 exits on the first write() error. mpv > > for example, or mplayer as you said, do not have this problem. > > > > My first guess would be that the error is generated during the > > hot-unpluging, because in the time window between the device detach and > > the switch to the new default device, write() will have failed since the > > device stopped doing IO at this point. That is not wrong behavior on > > sound(4)'s side though. > > > > > On the other hand, multimedia/mplayer does work, switching seamlessly > > > between the laptop speaker and headset. > > Just to make sure, the switching is successful even during IO, right? > Yes, with mplayer, switching works fine, both plugging and unplugging, while > playing an mp3 file. > > > Jakob > > > > > > On 2025-04-06 21:08, Christos Margiolis wrote: > > > > I've been working on a patch [1] to re-implement /dev/dsp as a > > > > router/virtual device. The commit message in the review explains all the > > > > high-level details and reasons behind the patch. This is the first of a > > > > series of patches I'm working on. > > > > > > > > For regular users, the main functional difference is that with this > > > > patch, /dev/dsp is an actual router device (like when using > > > > virtual_oss), which means that we have hot-swapping (i.e., changing the > > > > default device and routing audio to it during IO without needing to > > > > close and re-open /dev/dsp) built into sound(4). > > > > > > > > Feel free to test the patch and please let me know if there's anything > > > > that breaks or could be improved. You can play around with it just by > > > > recording/playing audio as you always do, try some hot-swaps, > > > > hot-(un)plugs, and anything that can stress test it. Just make sure you > > > > open /dev/dsp, which should be the default for most applications anyway. > > > > > > > > Christos > > > > > > > > [1] https://reviews.freebsd.org/D49216 > > Christos Christoshome | help
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