[snd-dice] latency 13 times higher compared to FFADO (Saffire 14 PRO) with jack2

[grinness]

Hi,

On a 5900x, 32 GB RAM, Archlinux (kernel 6.0.2), I have been investigating crazy high latency using a pipewire-jack, see:

https://gitlab.freedesktop.org/pipewire/pipewire/-/issues/2790

I ended up testing jack_iodelay with jack2, comparing snd-dice and FFADO

Running qjackctl jack2, ALSA backed (snd-dice) 48000Hz, 1024 samples, 2 periods:

> jack_iodelay                                                                                                                                                                                                                                                                                                                           
new capture latency: [0, 0]
new playback latency: [0, 0]
Signal below threshold...
Signal below threshold...
new capture latency: [1024, 1024]
Signal below threshold...
Signal below threshold...
new playback latency: [2048, 2048]
  5198.818 frames    108.309 ms total roundtrip latency
        extra loopback latency: 2126 frames
        use 1063 for the backend arguments -I and -O Inv
  5198.818 frames    108.309 ms total roundtrip latency
        extra loopback latency: 2126 frames
        use 1063 for the backend arguments -I and -O ?? Inv

Running qjackctl jack2, firewire backend (FFADO) 4800, 512 samples, 2 periods:

> jack_iodelay                                                                                                                                                                                                                                                                                                                                    
new capture latency: [0, 0]
new playback latency: [0, 0]
Signal below threshold...
new capture latency: [1024, 1024]
Signal below threshold...
new playback latency: [3072, 3072]
  4258.811 frames     88.725 ms total roundtrip latency
        extra loopback latency: 162 frames
        use 81 for the backend arguments -I and -O Inv
  4258.812 frames     88.725 ms total roundtrip latency
        extra loopback latency: 162 frames
        use 81 for the backend arguments -I and -O Inv

Note that qjackctl seems to not set the number of periods correctly with firewire backend, the above playback latency suggests 3 periods instead of 2. It seems that Cadence fixes the issue, but the extra loopback latency stays at 162 frames with FFADO

Thanks

[takaswie]

Let me close the issue since the reporter resigned from original issue in pipewire.