Encoding and bandwidth used by RAAT

I’m using Roon at work over a VPN and just curious:

  • What are the actual bandwidth figures for RAAT?
  • Also what codec does RAAT use for Roon to Roon playback of media?
  • Does RAAT send pure uncompressed PCM, FLAC, the original stream etc.?

Just to document my (very anecdotal) figures RAAT is using ~350KiB/s for streaming CD quality FLAC and ~450KiB/s for 24/96 audio.

By comparison Airplay is using ~150KiB/s.

Edit. corrected units and figures.

There is a lot on RAAT in the Knowledge Base.

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Unless I’ve missed something I don’t see anything which illuminates.

Just saying it explains about RAAT the why’s and wherefore’s

Just want to confirm your units here. Do you mean kilobits/second or kiloBYTES/second?

In either case the numbers don’t make a lot of sense as in Kb/sec both (especially 24/96) indicate significant compression (which doesn’t jive with CPU usage on the endpoint) and in KB/sec both indicate pretty significant overhead (over 4X for 16/44).

I do monitor this traffic occasionally and have found that my core is sending data to endpoints at rates that are commensurate with the data rate of the resolution being played (~1.4mbit/sec for 16/44 and ~4.6mbit/sec for 24/96)

Meant KiB (so kibibytes).

You’re right I was accidentally counting 2x the true value (read the aggregate over WiFi and VPN rather than the individual traffic over just VPN). Corrected the figures in my original post.

Could be some some overhead from the VPN but it actually compresses the link so if anything it might be under-reporting ever so slightly.

According to here 1x speed CD data is 150 KiB/s. Airplay is Apple Lossless so at worst it’d also be 150 KiB/s which corresponds to my own observations.

Would love for someone from Roon to weigh in with some hard figures though :smiley:

RAAT sends uncompressed PCM/DSD. There’s some minor overhead for packet headers too.

So CD quality FLAC should be 172.26KiB ((44100Hz * 16 bits per sample * 2 channels)/(8 bits per byte * 1024 bytes per KiB)) overhead.

AirPlay does ALAC compression which is why it’s beating that number. Compression/decompression increases CPU usage on the core a lot and the endpoint a good bit too. Our focus is local networks–the evils outweigh the good.

When we do a proper remote access/WAN solution, we will manage this differently. But that’s a different set of design goals/engineering work.

Thanks for the info Brian - I know you guys are busy so appreciate you satisfying our technical curiosity here. Also good to hear you’ve got remote access on your radar, wasn’t certain if that was something which Roon would be doing.