There has been some discussion on the Touch forum about the EDO app and the potential benfits to audio quality from the spdif output at 96k and below. This is not the primary purpose of the enhanced digital ouput app but people have debated whether any possible change in audio quality exists. I throught it would be useful to spell out what the changes are that are in EDO. As I may speculate about any impact on sound quality, I thought I'd do it here as its definately a discussion for the audiophile forum.
EDO essentially comprises three parts: 1) A custom linux kernel which is the standard Logitech kernel with the following changes: - spdif - additional clock divider values to allow 176.4/192k playback - usb scheduler - minor changes including change of default compilation options to allow most dacs to connect to usb - usb audio - major changes to include most of the more recent linux kernel changes that support uac2 - experimental alternative kernel idle routine 2) A squeezeplay applet which allows the kernel to be installed and provides menus to select the output device. It also starts up the audio output of squeezeplay and uses does a couple of things differently from standard squeezeplay: - it does not start an effects jive_alsa process (it is assumed users don't want to hear the effects processing) - it bypasses the alsa plug layer and uses the spdif output "TXRX" directly, simplifying the amout of processing required between jive_alsa and the spdif output driver - increases the priority of the irq task associated with the spdif driver (primarily to improve performance for 192k playback) 3) A new jive_alsa binary which adds support for additional alsa formats for packing samples into asla frames - this is necessary for the usb dac support, but there are no changes which I believe would impact spdif. Now I don't claim sound quality improvements from any of these for spdif playback and I have not done any critical listening for this. I would also not want to make any claims without being able to measure the circuit in more detail. However you could speculate about the following: - not sending output to the analog will avoid there being any data sent to the internal dac and avoid any data related load on this part of the circuit/psu - bypassing the alsa plug layer will reduce cpu load - not having a second jive_alsa process running reduces cpu load slightly However all these could be achieved with TT3 (I don't run it, but reading the code it looks like it will do this and much more) So its probably best to see EDO as doing the more obvious bits of TT3 to me. There is one other component of the app which is dissabled by default and is a complete experiement - this is the kernel idle option. This can be turned on from Settings > Advanced > Digital Output. What it does is subsitute the default kernel idle task (which allows the cpu to enter low power mode) for an alternative one (which does not enter low power mode). I speculate that if cpu load has an impact on sound quality then this should have an impact less than 100% cpu means the idle task is being run. I would be very interested if people can tell the difference with it enabled or not.... ------------------------------------------------------------------------ Triode's Profile: http://forums.slimdevices.com/member.php?userid=17 View this thread: http://forums.slimdevices.com/showthread.php?t=94855 _______________________________________________ audiophiles mailing list audiophiles@lists.slimdevices.com http://lists.slimdevices.com/mailman/listinfo/audiophiles
