'Twas brillig, and Frederik Vogelsang at 01/08/11 13:38 did gyre and gimble: > Hi, > > I'd like to know how I can dynamically switch between profiles > depending on the number of audio channels of the file being played. > > My output-sink currently has two profiles: > * Digital Stereo Output > * 5.1 AC3 Output > > Now I'd like to use the Stereo Output for normal PCM sources and the > 5.1 Output for multichannel sources. Is there a way to do that with > PulseAudio? > > With pure ALSA this can be done easily with the definition of a > "pcm.!surround51"-device in the .asoundrc, but I'd like to use > PulseAudio for obvious reasons. Dynamic profile switching is not currently supported, but it will be in the future. At present we're concentrating on passthough as that's generally what people have asked for more and it it semi related to this issue. If we add passthrough into the mix we may have the following list of preferences: 1. Media Player requests DTS passthrough -> PA Accepts as the user has said their receiver supports it and we are using the Digital Stereo Output profile. 2. Media Player requests DTS passthrough -> PA Rejects as the user has not said their receiver supports it. Media Player requests AC3 passthrough -> Ditto Media Player requests 6 channel PCM surround -> PA Switches to the AC3 Profile and accepts 6ch PCM input. As you can see the negotiation becomes far more complex... in step three above, why would PA prefer the 5.1 AC3 over the 5.1 Analog for example? To be honest there are a heap of problems surrounding this logic just now, which also focuses on jack detection. I can't really comment more on the issues as they are broad and complicated, but we'll all be meeting up at the Desktop Summit in a couple weeks, so we'll be taking issues like this forward a little then, and hopefully come up with coherent plans to deal with this kind of thing! At the moment, I'm not massively in favour of doing automatic profile switching at all and rather just dealing more gracefully with the disabling of upmixing. The AC3 encoder output is a bit of a stick in the mud here tho', as it's got a kind special use case... I'm not really sure how best to deal with that one :s Col -- Colin Guthrie gmane(at)colin.guthr.ie http://colin.guthr.ie/ Day Job: Tribalogic Limited [http://www.tribalogic.net/] Open Source: Mageia Contributor [http://www.mageia.org/] PulseAudio Hacker [http://www.pulseaudio.org/] Trac Hacker [http://trac.edgewall.org/]
