On 01/29/2016 11:46 PM, theo wrote: > Hi, > > First of all, let me introduce myself. I'm Theo, and while I'm new to > linux audio, I'm not new to linux perse (20+Y), and in general can find > my way around the system quite easily. Up until recently I've not had > much reason to delve into linux audio as It "just worked" for what I use > it for - listening to music while doing stuff behind the PC - which I > happen to do quite often as I'm working as a geneticist/bio-informatician. > > And then something changed. I bought a new laptop, and found the audio > quality "lacking" to say the least. So I went to the shop and got myself > a USB external sound card with reasonable sound quality and - worth > bonus points - a 6.35mm headphone jack instead of a 3.5mm jack, a volume > control dial and an extra pair of rca outputs so I can also connect it > to my stereo. I plugged it in and found out it didn't "just work". > > So I started reading up and was stupefied - it was an alien world to me, > with a new language (ok, new slang) and apparently several "competing" > ways of doing things. To make this manageable for myself I decided to > take things one step at a time. I first installed jack/qjackct, qsynth > and found a midi keyboard and got it to produce sound after some small > tweaks. Things have definitely changed a great deal since I last handled > a DX7 - and it was great fun. In the process I found out that channel 1 > and 2 of my USB sound thingy went to the rca outputs and channel 3 and 4 > to the headphone jack. No problem. > > Then I started gstreamer - no output. So I made some more tweaks as per > google's suggestions, then gstreamer outputs appeared in qjackctl, and > after making the necessary connections from gstreamer to outputs 3 and 4 > I had sound again. Great. Then the next song started playing and the > sound ceased. So I made the connections again in qjackctl and I had > sound again. This happened a few times, I got a bit annoyed and > discovered the patch bay. I tried it, and it didn't work on my usb > thingy while it worked flawlessly on my built-in sound card. Every time > a new song started, the connections in qjackctl automatically reverted > to output channels 1 and 2 (rca jacks) and disconnected channels 3 and 4 > (headphone) even though there was a patch-bay active. Now, I was almost > ready to file a bug report when I noticed that the patch bay did work > after a restart of gstreamer - for one song only. > > It was then that I realized that every song a new out_jackaudiosinkN_1 > and out_jackaudiosinkN_2 appeared in qjackctl, with N an increasing > integer. So in the patch bay I added out_jackaudiosink2_1, > out_jackaudiosink2_2, out_jackaudiosink5_1 and out_jackaudiosink5_2, and > connected them to my headphone outputs, and sure enough, after every > restart of gstreamer I could hear the second and fifth number, while all > other songs were silent. Quite a bit of fiddling later I found out that > one can actually use regular expressions in the patch-bay. Connecting > out_jackaudiosink[0-9]+_1 and out_jackaudiosink[0-9]+_2 to channel 3 and > 4 works. Wonderful. I now reliably get output through my headphones > after a new song starts. Only thing is that now I get four connections - > the (apparently) default connections to channels 1 and 2 are also > reconnected every time a new song starts. > > So, to come to my questions: > - Am I the only one using 4-channel external USB sound card with > gstreamer? When I saw it's specs I was convinced that everyone would > want one as a sort of "audio docking station" - better quality audio and > no more annoying physical (un)plugging to re-route audio through an > amplifier on the wrong side of the room instead of headphones. > - What is the point of this (re-)connection behaviour of gstreamer? - > gstreamer doesn't suddenly become a "new device" when it starts playing > a new song. > - I guess gstreamer does the out_jackaudiosinkN_x numbering, correct? > VLC seems to handle this differently (and this is actually how I found > out about the regular expressions) > - How can I tell the software (gstreamer + jack) to do what I want and > not more? Simply a connection from gstreamer to my headphones (channel 3 > and 4), and NOT to my RCA connectors as well unless I tell it to. This > last question may appear a bit mute as it now "just works" in my main > use case (headphones), but it bugs me that I have a device that would > perfectly allow me to keep my amplifier plugged in ready to roll at a > software flick of switch, but if I would, every new song starting would > automatically come blaring out of my speakers. I guess that others have > bumped in this as well - in particular people doing DJ-ing from from > linux (do they exist?) would get very annoyed by sound coming out the > wrong way every time a new song starts. > - I found little in terms of usable documentation for multi-output > set-ups. I'm for instance not convinced that I would be able to > configure the system to use both on-board and external usb sound-cards > simultaneously. Did I miss something here? Can anyone point me to some > relevant documentation or is there a real issue here? Also the regular > expressions bit - quite neat - but I just stumbled upon its' use in > another program, and is not something I read about. > > In general I'm both impressed by and worried about the state of linux > audio - a lot is possible but to get things working is (imho) much > harder than it should be. Hello Theo, Welcome to the list! Why would you need Gstreamer and JACK for playing songs? Why not just use PulseAudio? Or am I missing something? Jeremy
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