SND_HDSP(4)

NAME
snd_hdsp - RME HDSP bridge device driver

SYNOPSIS
To compile this driver into the kernel, place the following lines in your kernel configuration file:

device sound
device snd_hdsp

Alternatively, to load the driver as a module at boot time, place the following line in loader.conf(5):

    snd_hdsp_load="YES"

DESCRIPTION
The snd_hdsp bridge driver allows the generic audio driver sound(4) to attach to RME HDSP audio devices.

HARDWARE
The snd_hdsp driver supports the following audio devices:

•   RME HDSP 9632 (optional AO4S-192 and AIS-192 extension boards)
•   RME HDSP 9652

By default, each pcm(4) device corresponds to a physical port on the sound card. For ADAT ports, 8 channel, 4 channel and 2 channel formats are supported. The effective number of ADAT channels is 8 channels at single speed (32kHz-48kHz) and 4 channels at double speed (64kHz-96kHz). Only the HDSP 9632 can operate at quad speed (128kHz-192kHz), ADAT is disabled in this mode. Depending on sample rate and channel format selected, not all pcm channels can be mapped to ADAT channels and vice versa.

LOADER TUNABLES
These settings can be entered at the loader(8) prompt or in loader.conf(5).

hw.hdsp.unified_pcm
    If set to 1, all physical ports are combined into one unified pcm device. When opened in multi-channel audio software, this makes all ports available at the same time, and fully synchronized. For resulting channel numbers consult the following table:
Sound Card | Single Speed | Double Speed | Quad Speed
 | Play | Rec | Play | Rec | Play | Rec
HDSP 9632 | 16 | 16 | 12 | 12 | 8 | 8
HDSP 9652 | 26 | 26 | 14 | 14 | - | -

SYSCTL TUNABLES
These settings and informational values can be accessed at runtime with the sysctl(8) command. If multiple RME HDSP sound cards are installed, each device has a separate configuration. To adjust the following sysctl identifiers for a specific sound card, insert the respective device number in place of ‘0’.

dev.hdsp.0.sample_rate
    Set a fixed sample rate from 32000, 44100, 48000, up to 192000. This is usually required for digital connections (AES, S/PDIF, ADAT). The default value of 0 adjusts the sample rate according to pcm device settings.

dev.hdsp.0.period
    The number of samples processed per interrupt, from 32, 64, 128, up to 4096. Setting a lower value here results in less latency, but increases system load due to frequent interrupt processing. Extreme values may cause audio gaps and glitches.

dev.hdsp.0.clock_list
    Lists possible clock sources to sync with, depending on the hardware model. This includes internal and external master clocks as well as incoming digital audio signals like AES, S/PDIF and ADAT.

dev.hdsp.0.clock_preference
    Select a preferred clock source from the clock list. HDSP cards will sync to this clock source when available, but fall back to auto-sync with any other digital clock signal they receive. Set this to ‘internal’ if the HDSP card should act as master clock.

dev.hdsp.0.clock_source
    Shows the actual clock source in use (read only). This differs from what is set as clock preference when in auto-sync mode.

dev.hdsp.0.sync_status
    Display the current sync status of all external clock sources. Status indications are ‘none’ for no signal at all, ‘lock’ for when a valid signal is present, and ‘sync’ for accurately synchronized signals (required for recording digital audio).

The following tunables are applicable to HDSP 9632 devices only:

dev.hdsp.0.input_level
    Select the sensitivity of the analog line input. Available reference levels for the input signal are ‘LowGain’, ‘+4dBu’ and ‘-10dBV’.

dev.hdsp.0.output_level
    Select the gain level of the analog line output. Available reference levels for the output signal are ‘HighGain’, ‘+4dBu’ and ‘-10dBV’.

dev.hdsp.0.phones_level
    Adjust the gain level of the phones output, separately from the analog line output. The signal can be lowered by 6 or 12 dB.

Where appropriate these sysctl values are modeled after official RME software on other platforms, and adopt their terminology. Consult the RME user manuals for additional information.

SEE ALSO
sound(4)

HISTORY
The snd_hdsp device driver first appeared in FreeBSD 15.0.

AUTHORS
-nosplit Based on snd_hdspe(4) originally written by Ruslan Bukin <br@bsdpad.com>. All adaptation to HDSP cards by Florian Walpen <dev@submerge.ch>.