alsa-project/alsa-lib issue #280 was opened from grinness:

Hi,

I hope this is the right place to report this (please let me know if it is not) 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: ```

jack_iodelay

new capture latency: [0, 0] new playback latency: [0, 0] Signal below threshold... Signal below threshold... Signal below threshold... Signal below threshold... Signal below threshold... Signal below threshold... new capture latency: [512, 512] 8354.799 frames 174.058 ms total roundtrip latency extra loopback latency: 7842 frames use 3921 for the backend arguments -I and -O ?? Inv 8354.779 frames 174.058 ms total roundtrip latency extra loopback latency: 7842 frames use 3921 for the backend arguments -I and -O Inv Signal below threshold... Signal below threshold... new playback latency: [1024, 1024] Signal below threshold... 1698.777 frames 35.391 ms total roundtrip latency extra loopback latency: 162 frames use 81 for the backend arguments -I and -O Inv 1698.777 frames 35.391 ms total roundtrip latency extra loopback latency: 162 frames use 81 for the backend arguments -I and -O Inv 1698.777 frames 35.391 ms total roundtrip latency extra loopback latency: 162 frames use 81 for the backend arguments -I and -O Inv 1698.777 frames 35.391 ms total roundtrip latency extra loopback latency: 162 frames use 81 for the backend arguments -I and -O Inv 1698.777 frames 35.391 ms total roundtrip latency extra loopback latency: 162 frames

```

Please note that the pipewire developer pointed out that:

"My problem is that the period size in the driver is set to 1024. For batch devices and a quantum of 256 this should be set to 128 to get decent latency. So, either the driver does not report itself as batch, or something else started the nodes with a higher quantum. I'm betting it's the batch thing."

I also reported this in the following: https://github.com/takaswie/snd-firewire-improve/issues/47

thanks

Issue URL : https://github.com/alsa-project/alsa-lib/issues/280 Repository URL: https://github.com/alsa-project/alsa-lib