Would it be possible to have a client able to use the hardware decoding of the raspberry pi ?
It should be possible to use the omxplayer for that.
It should be possible, but since the code has not been used in any other projects but omxplayer, that's unlikely to happen unless someone submits some code.
In fact it might be better to use openmax : https://www.raspberrypi.org/forums/viewtopic.php?f=33&t=57721 or MMAL
I would love to try, but for now I really don't know were to start.
Just a question,
Why use gstreamer for audio decoding and not for video ?
Because seems to me that it would permit to have hardware decoding, even on the rpi with gst-omx...
Why use gstreamer for audio decoding and not for video ?
Audio is a stream that never stops so gstreamer is a good fit.
Screen updates are not always video, starting and stopping gstreamer pipelines for this would be too expensive - just not a good fit.
this ticket has been moved to: https://github.com/Xpra-org/xpra/issues/932