On Mon, 2013-09-09 at 22:14 +0300, Anssi Hannula wrote: > Hi, > > I was looking at using the PA passthrough support (and adding support > for TrueHD, DTS-HD), but it seems there is another issue that has to be > resolved first: > > Pulseaudio passthrough (with ALSA) does not currently work unless a > stereo profile is in use. > > If a HDMI surround profile is in use, the device seems to be permanently > in a 6 channel mode. As passthrough of e.g. 48kHz AC-3/DTS requires the > device to opened in 2 channel 48kHz mode, pa_sink_input_new() will > always fail with "Could not update sink sample spec to match passthrough > stream". The HDMI surround profile is a 6-channel profile, so it's expected that you can't open the device in 2-channel mode. If you want 2 channels, you need to activate a 2-channel profile. It would probably be good to change the profile automatically when a passthrough stream appears. > How should this be solved? > > > (also, TrueHD and DTS-HD MA will require a 768kHz IEC 60958 frame rate, > which in ALSA is 8 channel 192kHz) This will then require a 8-channel profile to be activated. > BTW, shouldn't/couldn't the sink channel count be auto-selected from > EDID in case of HDMI instead of having to select profiles? I suppose the HDMI device can be opened in many channel configurations, so I guess your question is about what should be the default channel count. I don't know what information EDID contains, but if it contains just the maximum supported number of channels, I'm not so sure it makes sense to default to a surround setup. Stereo mode is a safer default. -- Tanu
