d6e33796b5
Documentation Fixed obsolete description about CMIPCI driver. Signed-off-by: Takashi Iwai <tiwai@suse.de>
249 lines
8.9 KiB
Text
249 lines
8.9 KiB
Text
Brief Notes on C-Media 8738/8338 Driver
|
|
=======================================
|
|
|
|
Takashi Iwai <tiwai@suse.de>
|
|
|
|
|
|
Front/Rear Multi-channel Playback
|
|
---------------------------------
|
|
|
|
CM8x38 chip can use ADC as the second DAC so that two different stereo
|
|
channels can be used for front/rear playbacks. Since there are two
|
|
DACs, both streams are handled independently unlike the 4/6ch multi-
|
|
channel playbacks in the section below.
|
|
|
|
As default, ALSA driver assigns the first PCM device (i.e. hw:0,0 for
|
|
card#0) for front and 4/6ch playbacks, while the second PCM device
|
|
(hw:0,1) is assigned to the second DAC for rear playback.
|
|
|
|
There are slight difference between two DACs.
|
|
|
|
- The first DAC supports U8 and S16LE formats, while the second DAC
|
|
supports only S16LE.
|
|
- The seconde DAC supports only two channel stereo.
|
|
|
|
Please note that the CM8x38 DAC doesn't support continuous playback
|
|
rate but only fixed rates: 5512, 8000, 11025, 16000, 22050, 32000,
|
|
44100 and 48000 Hz.
|
|
|
|
The rear output can be heard only when "Four Channel Mode" switch is
|
|
disabled. Otherwise no signal will be routed to the rear speakers.
|
|
As default it's turned on.
|
|
|
|
*** WARNING ***
|
|
When "Four Channel Mode" switch is off, the output from rear speakers
|
|
will be FULL VOLUME regardless of Master and PCM volumes.
|
|
This might damage your audio equipment. Please disconnect speakers
|
|
before your turn off this switch.
|
|
*** WARNING ***
|
|
|
|
[ Well.. I once got the output with correct volume (i.e. same with the
|
|
front one) and was so excited. It was even with "Four Channel" bit
|
|
on and "double DAC" mode. Actually I could hear separate 4 channels
|
|
from front and rear speakers! But.. after reboot, all was gone.
|
|
It's a very pity that I didn't save the register dump at that
|
|
time.. Maybe there is an unknown register to achieve this... ]
|
|
|
|
If your card has an extra output jack for the rear output, the rear
|
|
playback should be routed there as default. If not, there is a
|
|
control switch in the driver "Line-In As Rear", which you can change
|
|
via alsamixer or somewhat else. When this switch is on, line-in jack
|
|
is used as rear output.
|
|
|
|
There are two more controls regarding to the rear output.
|
|
The "Exchange DAC" switch is used to exchange front and rear playback
|
|
routes, i.e. the 2nd DAC is output from front output.
|
|
|
|
|
|
4/6 Multi-Channel Playback
|
|
--------------------------
|
|
|
|
The recent CM8738 chips support for the 4/6 multi-channel playback
|
|
function. This is useful especially for AC3 decoding.
|
|
|
|
When the multi-channel is supported, the driver name has a suffix
|
|
"-MC" such like "CMI8738-MC6". You can check this name from
|
|
/proc/asound/cards.
|
|
|
|
When the 4/6-ch output is enabled, the second DAC accepts up to 6 (or
|
|
4) channels. While the dual DAC supports two different rates or
|
|
formats, the 4/6-ch playback supports only the same condition for all
|
|
channels. Since the multi-channel playback mode uses both DACs, you
|
|
cannot operate with full-duplex.
|
|
|
|
The 4.0 and 5.1 modes are defined as the pcm "surround40" and "surround51"
|
|
in alsa-lib. For example, you can play a WAV file with 6 channels like
|
|
|
|
% aplay -Dsurround51 sixchannels.wav
|
|
|
|
For programmin the 4/6 channel playback, you need to specify the PCM
|
|
channels as you like and set the format S16LE. For example, for playback
|
|
with 4 channels,
|
|
|
|
snd_pcm_hw_params_set_access(pcm, hw, SND_PCM_ACCESS_RW_INTERLEAVED);
|
|
// or mmap if you like
|
|
snd_pcm_hw_params_set_format(pcm, hw, SND_PCM_FORMAT_S16_LE);
|
|
snd_pcm_hw_params_set_channels(pcm, hw, 4);
|
|
|
|
and use the interleaved 4 channel data.
|
|
|
|
There are some control switchs affecting to the speaker connections:
|
|
|
|
"Line-In Mode" - an enum control to change the behavior of line-in
|
|
jack. Either "Line-In", "Rear Output" or "Bass Output" can
|
|
be selected. The last item is available only with model 039
|
|
or newer.
|
|
When "Rear Output" is chosen, the surround channels 3 and 4
|
|
are output to line-in jack.
|
|
"Mic-In Mode" - an enum control to change the behavior of mic-in
|
|
jack. Either "Mic-In" or "Center/LFE Output" can be
|
|
selected.
|
|
When "Center/LFE Output" is chosen, the center and bass
|
|
channels (channels 5 and 6) are output to mic-in jack.
|
|
|
|
Digital I/O
|
|
-----------
|
|
|
|
The CM8x38 provides the excellent SPDIF capability with very cheap
|
|
price (yes, that's the reason I bought the card :)
|
|
|
|
The SPDIF playback and capture are done via the third PCM device
|
|
(hw:0,2). Usually this is assigned to the PCM device "spdif".
|
|
The available rates are 44100 and 48000 Hz.
|
|
For playback with aplay, you can run like below:
|
|
|
|
% aplay -Dhw:0,2 foo.wav
|
|
|
|
or
|
|
|
|
% aplay -Dspdif foo.wav
|
|
|
|
24bit format is also supported experimentally.
|
|
|
|
The playback and capture over SPDIF use normal DAC and ADC,
|
|
respectively, so you cannot playback both analog and digital streams
|
|
simultaneously.
|
|
|
|
To enable SPDIF output, you need to turn on "IEC958 Output Switch"
|
|
control via mixer or alsactl ("IEC958" is the official name of
|
|
so-called S/PDIF). Then you'll see the red light on from the card so
|
|
you know that's working obviously :)
|
|
The SPDIF input is always enabled, so you can hear SPDIF input data
|
|
from line-out with "IEC958 In Monitor" switch at any time (see
|
|
below).
|
|
|
|
You can play via SPDIF even with the first device (hw:0,0),
|
|
but SPDIF is enabled only when the proper format (S16LE), sample rate
|
|
(441100 or 48000) and channels (2) are used. Otherwise it's turned
|
|
off. (Also don't forget to turn on "IEC958 Output Switch", too.)
|
|
|
|
|
|
Additionally there are relevant control switches:
|
|
|
|
"IEC958 Mix Analog" - Mix analog PCM playback and FM-OPL/3 streams and
|
|
output through SPDIF. This switch appears only on old chip
|
|
models (CM8738 033 and 037).
|
|
Note: without this control you can output PCM to SPDIF.
|
|
This is "mixing" of streams, so e.g. it's not for AC3 output
|
|
(see the next section).
|
|
|
|
"IEC958 In Select" - Select SPDIF input, the internal CD-in (false)
|
|
and the external input (true).
|
|
|
|
"IEC958 Loop" - SPDIF input data is loop back into SPDIF
|
|
output (aka bypass)
|
|
|
|
"IEC958 Copyright" - Set the copyright bit.
|
|
|
|
"IEC958 5V" - Select 0.5V (coax) or 5V (optical) interface.
|
|
On some cards this doesn't work and you need to change the
|
|
configuration with hardware dip-switch.
|
|
|
|
"IEC958 In Monitor" - SPDIF input is routed to DAC.
|
|
|
|
"IEC958 In Phase Inverse" - Set SPDIF input format as inverse.
|
|
[FIXME: this doesn't work on all chips..]
|
|
|
|
"IEC958 In Valid" - Set input validity flag detection.
|
|
|
|
Note: When "PCM Playback Switch" is on, you'll hear the digital output
|
|
stream through analog line-out.
|
|
|
|
|
|
The AC3 (RAW DIGITAL) OUTPUT
|
|
----------------------------
|
|
|
|
The driver supports raw digital (typically AC3) i/o over SPDIF. This
|
|
can be toggled via IEC958 playback control, but usually you need to
|
|
access it via alsa-lib. See alsa-lib documents for more details.
|
|
|
|
On the raw digital mode, the "PCM Playback Switch" is automatically
|
|
turned off so that non-audio data is heard from the analog line-out.
|
|
Similarly the following switches are off: "IEC958 Mix Analog" and
|
|
"IEC958 Loop". The switches are resumed after closing the SPDIF PCM
|
|
device automatically to the previous state.
|
|
|
|
On the model 033, AC3 is implemented by the software conversion in
|
|
the alsa-lib. If you need to bypass the software conversion of IEC958
|
|
subframes, pass the "soft_ac3=0" module option. This doesn't matter
|
|
on the newer models.
|
|
|
|
|
|
ANALOG MIXER INTERFACE
|
|
----------------------
|
|
|
|
The mixer interface on CM8x38 is similar to SB16.
|
|
There are Master, PCM, Synth, CD, Line, Mic and PC Speaker playback
|
|
volumes. Synth, CD, Line and Mic have playback and capture switches,
|
|
too, as well as SB16.
|
|
|
|
In addition to the standard SB mixer, CM8x38 provides more functions.
|
|
- PCM playback switch
|
|
- PCM capture switch (to capture the data sent to DAC)
|
|
- Mic Boost switch
|
|
- Mic capture volume
|
|
- Aux playback volume/switch and capture switch
|
|
- 3D control switch
|
|
|
|
|
|
MIDI CONTROLLER
|
|
---------------
|
|
|
|
The MPU401-UART interface is disabled as default. You need to set
|
|
module option "mpu_port" with a valid I/O port address to enable the
|
|
MIDI support. The valid I/O ports are 0x300, 0x310, 0x320 and 0x330.
|
|
Choose the value which doesn't conflict with other cards.
|
|
|
|
There is _no_ hardware wavetable function on this chip (except for
|
|
OPL3 synth below).
|
|
What's said as MIDI synth on Windows is a software synthesizer
|
|
emulation. On Linux use TiMidity or other softsynth program for
|
|
playing MIDI music.
|
|
|
|
|
|
FM OPL/3 Synth
|
|
--------------
|
|
|
|
The FM OPL/3 is also enabled as default only for the first card.
|
|
Set "fm_port" module option for more cards.
|
|
|
|
The output quality of FM OPL/3 is, however, very weird.
|
|
I don't know why..
|
|
|
|
|
|
Joystick and Modem
|
|
------------------
|
|
|
|
The legacy joystick is supported. To enable the joystick support, pass
|
|
joystick_port=1 module option. The value 1 means the auto-detection.
|
|
If the auto-detection fails, try to pass the exact I/O address.
|
|
|
|
The modem is enabled dynamically via a card control switch "Modem".
|
|
|
|
|
|
Debugging Information
|
|
---------------------
|
|
|
|
The registers are shown in /proc/asound/cardX/cmipci. If you have any
|
|
problem (especially unexpected behavior of mixer), please attach the
|
|
output of this proc file together with the bug report.
|