Hans Verkuil wrote: > On Wednesday 10 May 2006 22:10, Perry Gilfillan wrote: > >> I'm trying to understand the physical paths of the audio RCA >> connectors for tv-out on the PVR-350. >> >> My expectation was that the decoded MPEG stream audio from the >> cx2341x decoder is routed to the msp44xx sound processor. If this is >> the case then snd-tvmixer [ http://www.gilfillan.org/v3tv/ALSA/ ] >> might be able to control the volume. No joy yet. >> > > No, the output goes straight from the MPEG decoder to the audio-out > cable. The mspx4xx controls the recording level for the MPEG encoder > (the audio input side). > Thanks, that's the simple answer I could not find. I'll add it to the wiki's that left me wondering...
I don't see much point in this case to exposing the mspx4xx mixer to the user via snd-tvmixer. Imagine the chaos when they inadvertently tweak the mute and wonder why recordings fail. But it is possible. > >> I did finally do the obvious 'Watch TV' test and find that >> snd-tvmixer DOES control the PVR-350's encoder audio. Changes to the >> volume in alsamixer are delayed by the latency introduced by >> buffering. >> >> I've found reference to using ivtvctl to control volume on the >> tv-out, but that only affects the encoding stream, not the tv-out. >> >> TV-out with X is working well. I'm not using the ivtvdev xdriver >> yet. There is no sound card, so patching the audio through another >> mixer device does not enter into the discussion. >> >> The system in question is running Gentoo. I've been running with >> kernel 2.6.14-gentoo-r4 and ivtv-0.4.0-r3. I've just installed >> gentoo-sources-2.6.16-r7 and ivtv 0.6.2 from svn. The newer versions >> have the same result that ivtvctl and snd-tvmixer are unable to >> affect the volume at the tv-out connectors. >> >> >> The question remains, does the audio from the MPEG decoder go through >> any device on the PVR-350 that would provide volume control before >> reaching the RCA sockets? >> >> I saw nothing in fw-decoder-api.txt about volume. Does the cx23415 >> MPEG audio decode stage provide any DSP functions? >> > > No. > > Well, that should clear up things :-) > > Regards, > > Hans > > _______________________________________________ ivtv-devel mailing list [email protected] http://ivtvdriver.org/mailman/listinfo/ivtv-devel
