DTS Passthrough over HDMI with ALSA

[wilko]

Hello all,

I am interested in using the Pi's HDMI connection to transport 5.1 channel sound. My investigations so far suggest that it is impossible to output 6 channels of PCM data, so I am now looking at using DTS. I have a decoder with HDMI inputs, and I am interested in audio only.

Currently, I can use dcaenc (aepatrakov.narod.ru/dcaenc/) to encode PCM data to a DTS file. Using omxplayer -o hdmi -p <filename>
I can output these files without re-encoding and down-mixing, and everything works correctly. However, I need to do the conversion on the fly.

I would like to use the dcaenc ALSA plugin to do the encoding, but I can't figure out how ALSA should be configured to allow this on the Pi (or if it is possible).

If it is possible, how would this be done?
Or alternatively, is there an OpenMax application that would provide this same functionality?

[dom]

I believe the /opt/vc/src/hello_pi/hello_audio can be trivially changed to output six channel PCM over hdmi.

[wilko]

Thanks very much, completely solves my problem... I feel like a total noob now.

Given that this is possible, why exactly can't omxplayer or ALSA seem to manage this?

Also, as it may be useful for people without hdmi inputs on their decoders (and who are using a splitter), is there a simple tool for dts passthrough? Otherwise, I may write one in the future.

[dom]

Given that this is possible, why exactly can't omxplayer or ALSA seem to manage this?

Some discussion here:
https://github.com/huceke/omxplayer/issues/125