Documentation/sound/cards/emu-mixer.rst

Source file repositories/reference/linux-study-clean/Documentation/sound/cards/emu-mixer.rst

File Facts

System
Linux kernel
Corpus path
Documentation/sound/cards/emu-mixer.rst
Extension
.rst
Size
8909 bytes
Lines
227
Domain
Support Tooling And Documentation
Bucket
Documentation
Inferred role
Support Tooling And Documentation: documentation
Status
atlas-only

Why This File Exists

Repository support layer: documentation, build tooling, samples, user-space helper tools, generated initramfs support, licenses, and validation utilities.

Dependency Surface

Detected Declarations

Annotated Snippet

==================================================
E-MU Digital Audio System mixer / default DSP code
==================================================

This document covers the E-MU 0404/1010/1212/1616/1820 PCI/PCI-e/CardBus
cards.

These cards use regular EMU10K2 (SoundBlaster Audigy) chips, but with an
alternative front-end geared towards semi-professional studio recording.

This document is based on audigy-mixer.rst.


Hardware compatibility
======================

The EMU10K2 chips have a very short capture FIFO, which makes recording
unreliable if the card's PCI bus requests are not handled with the
appropriate priority.
This is the case on more modern motherboards, where the PCI bus is only a
secondary peripheral, rather than the actual arbiter of device access.
In particular, I got recording glitches during simultaneous playback on an
Intel DP55 board (memory controller in the CPU), but had success with an
Intel DP45 board (memory controller in the north bridge).

The PCI Express variants of these cards (which have a PCI bridge on board,
but are otherwise identical) may be less problematic.


Driver capabilities
===================

This driver supports only 16-bit 44.1/48 kHz operation. The multi-channel
device (see emu10k1-jack.rst) additionally supports 24-bit capture.

A patchset to enhance the driver is available from `a GitHub repository
<https://github.com/ossilator/linux/tree/ossis-emu10k1>`_.
Its multi-channel device supports 24-bit for both playback and capture,
and also supports full 88.2/96/176.4/192 kHz operation.
It is not going to be upstreamed due to a fundamental disagreement about
what constitutes a good user experience.


Digital mixer controls
======================

Note that the controls work as attenuators: the maximum value is the neutral
position leaving the signal unchanged. Note that if the same destination is
mentioned in multiple controls, the signal is accumulated and can be clipped
(set to maximal or minimal value without checking for overflow).

Explanation of used abbreviations:

DAC
	digital to analog converter
ADC
	analog to digital converter
LFE
	low frequency effects (used as subwoofer signal)
IEC958
	S/PDIF
FX-bus
	the EMU10K2 chip has an effect bus containing 64 accumulators.
	Each of the synthesizer voices can feed its output to these accumulators
	and the DSP microcontroller can operate with the resulting sum.

name='Clock Source',index=0
---------------------------
This control allows switching the word clock between internally generated
44.1 or 48 kHz, or a number of external sources.

Annotation

Implementation Notes