[11:30] <ogra> waveform, so digging a bit into the KMS future, i see that v4l2_m2m seems to be pretty well advanced already but i also see that for HW decoding we will need rpivid-v4l2.dtbo loaded, should we not have dtoverlay=rpivid-v4l2 set in sync as soon as we switch from fkms to kms ? 
[11:38] <waveform> ogra, probably on desktop (the only platform where kms is currently set), but I'm not sure how/whether it interferes with any of the legacy stuff which still works (to some extent). Another of those "more research needed" bits
[11:39] <ogra> yeah ... i'm starting to play with it ... prob is that you need all userspace apps patched too ... i.e. ffmpeg, kodi, vlc ... 
[11:39]  * ogra hugs snaps ... they make that easier ...
[11:41] <ogra> one other issue i have with KMS is that our pulse snap does not find HDMI devices anymore after switching to kms ... 
[11:41] <ogra> i guess there are also some patches needed
[11:41] <ogra> i realize that i can't stay in the past forever though 🙂
[11:41] <waveform> odd, given that pulse on the desktop image still finds the HDMI devices happily (in fact the audio is less choppy under kms than under fkms there -- it's one of the concerns I have with switching the impish desktop to fkms -- currently testing how bad it gets on different models)
[11:42] <waveform> and yes, the change is painful but it will result in a much more open eco-system for the pi, which can't be a bad thing long-term
[11:43] <ogra> funny, i never have choppy audio in ubuntu core with fkms and pulse from candidate (i do have to hack rthe tsched=0 thingie into it though)
[11:43] <waveform> ah, that's the thing -- with the tsched=0 hack: choppy audio under fkms (and the hack does fix it), but kms is not choppy (on the stock impish desktop) *without* the tsched=0 hack
[11:44] <ogra> definitely ... but i need to give template code to our customers so i need to understand how it works (at least on the surface) 
[11:44] <waveform> urgh, I meant *without* the tsched=0 hack -ooops
[11:46] <ogra> well, i see more audio devices in /proc/asound/cards when switching (there seem to be two upstream kernel devices too) but pulse (in the snap) only sees the headphone jack 
[11:46] <waveform> hmmm, sounds like a confinement issue
[11:47] <ogra> not sure ... i'll try switching it to devmode for a test ... 
[11:47] <ogra> (i wouldnt know why the confinement wouldnt make it find devices it usually has access to )
[11:48] <waveform> presumably because under kms they're "different devices" to those under fkms (different kernel driver, resulting in a different device? Though ALSA/pulse may label them the same, the underlying path is presumably different)
[11:49] <ogra> right ... i suspect it is more on the alsa level than pulse actually 
[11:49] <ogra> with kms enabled i have vc4hdmi and vc4hdmi1 ... and headphones ... pulse doesnt see the vc4hdmi ones
[11:54] <ogra> nope, devmode doesnt seem to change anything ... so not confinement ... 
[11:55] <ogra> well, at least the headphone jack works ... (not helpful for TV audio indeed, but pulse itself seems to work)
[11:58] <ogra> i see pulse shipd the whole of /usr/share/alsa in the snap, do we have any special handling in the alsa configs for teh pi that 20.04 didnt have ? 
[12:00] <waveform> not that I'm aware of, but alsa is typically desktop team so perhaps they've added some I don't know about?
[12:01] <ogra> i cant imagine that ... 
[12:01] <ogra> they dont go out on their own to fiddle with pi stuff i think 🙂
[12:01] <waveform> not generally, no -- still if it's not confinement it's worth a look
[12:02] <ogra> yeah ... all the bits on UC are 20.04 though ... so any fixes that came in later will not be included yet 
[12:03] <waveform> good point
[12:05] <ogra> https://git.alsa-project.org/?p=alsa-lib.git;a=blob;f=src/conf/cards/vc4-hdmi.conf;h=027804a145d1ed9e4fe33dbb5fa7ef278230c328;hb=HEAD
[12:05] <ogra> aha !
[12:05] <ogra> so there is a special alsa config 
[12:22] <ogra> YAY !
[12:22] <ogra> so re-packing pulse with that file and manually setting the default sink to HDMI works ... 
[12:23] <ogra> (now, how do i make it default to HDMI instead of headphones
[12:23] <ogra> )
[12:25] <ogra> waveform, and you are correct, no tsched hack needed with that 
[12:26] <ogra> next stop ... roll an ffmpeg snap with v4l2-m2m support ... 
[12:26] <waveform> ah, a special config but upstream -- that makes sense
[12:26]  * ogra looks at https://github.com/popcornmix/FFmpeg/tree/deinterlace