1 Brief Notes on C-Media 8338/8738/8768/8770 Driver 2 ================================================= 3 4 Takashi Iwai <tiwai@suse.de> 5 6 7Front/Rear Multi-channel Playback 8--------------------------------- 9 10CM8x38 chip can use ADC as the second DAC so that two different stereo 11channels can be used for front/rear playbacks. Since there are two 12DACs, both streams are handled independently unlike the 4/6ch multi- 13channel playbacks in the section below. 14 15As default, ALSA driver assigns the first PCM device (i.e. hw:0,0 for 16card#0) for front and 4/6ch playbacks, while the second PCM device 17(hw:0,1) is assigned to the second DAC for rear playback. 18 19There are slight differences between the two DACs: 20 21- The first DAC supports U8 and S16LE formats, while the second DAC 22 supports only S16LE. 23- The second DAC supports only two channel stereo. 24 25Please note that the CM8x38 DAC doesn't support continuous playback 26rate but only fixed rates: 5512, 8000, 11025, 16000, 22050, 32000, 2744100 and 48000 Hz. 28 29The rear output can be heard only when "Four Channel Mode" switch is 30disabled. Otherwise no signal will be routed to the rear speakers. 31As default it's turned on. 32 33*** WARNING *** 34When "Four Channel Mode" switch is off, the output from rear speakers 35will be FULL VOLUME regardless of Master and PCM volumes. 36This might damage your audio equipment. Please disconnect speakers 37before your turn off this switch. 38*** WARNING *** 39 40[ Well.. I once got the output with correct volume (i.e. same with the 41 front one) and was so excited. It was even with "Four Channel" bit 42 on and "double DAC" mode. Actually I could hear separate 4 channels 43 from front and rear speakers! But.. after reboot, all was gone. 44 It's a very pity that I didn't save the register dump at that 45 time.. Maybe there is an unknown register to achieve this... ] 46 47If your card has an extra output jack for the rear output, the rear 48playback should be routed there as default. If not, there is a 49control switch in the driver "Line-In As Rear", which you can change 50via alsamixer or somewhat else. When this switch is on, line-in jack 51is used as rear output. 52 53There are two more controls regarding to the rear output. 54The "Exchange DAC" switch is used to exchange front and rear playback 55routes, i.e. the 2nd DAC is output from front output. 56 57 584/6 Multi-Channel Playback 59-------------------------- 60 61The recent CM8738 chips support for the 4/6 multi-channel playback 62function. This is useful especially for AC3 decoding. 63 64When the multi-channel is supported, the driver name has a suffix 65"-MC" such like "CMI8738-MC6". You can check this name from 66/proc/asound/cards. 67 68When the 4/6-ch output is enabled, the second DAC accepts up to 6 (or 694) channels. While the dual DAC supports two different rates or 70formats, the 4/6-ch playback supports only the same condition for all 71channels. Since the multi-channel playback mode uses both DACs, you 72cannot operate with full-duplex. 73 74The 4.0 and 5.1 modes are defined as the pcm "surround40" and "surround51" 75in alsa-lib. For example, you can play a WAV file with 6 channels like 76 77 % aplay -Dsurround51 sixchannels.wav 78 79For programming the 4/6 channel playback, you need to specify the PCM 80channels as you like and set the format S16LE. For example, for playback 81with 4 channels, 82 83 snd_pcm_hw_params_set_access(pcm, hw, SND_PCM_ACCESS_RW_INTERLEAVED); 84 // or mmap if you like 85 snd_pcm_hw_params_set_format(pcm, hw, SND_PCM_FORMAT_S16_LE); 86 snd_pcm_hw_params_set_channels(pcm, hw, 4); 87 88and use the interleaved 4 channel data. 89 90There are some control switches affecting to the speaker connections: 91 92"Line-In Mode" - an enum control to change the behavior of line-in 93 jack. Either "Line-In", "Rear Output" or "Bass Output" can 94 be selected. The last item is available only with model 039 95 or newer. 96 When "Rear Output" is chosen, the surround channels 3 and 4 97 are output to line-in jack. 98"Mic-In Mode" - an enum control to change the behavior of mic-in 99 jack. Either "Mic-In" or "Center/LFE Output" can be 100 selected. 101 When "Center/LFE Output" is chosen, the center and bass 102 channels (channels 5 and 6) are output to mic-in jack. 103 104Digital I/O 105----------- 106 107The CM8x38 provides the excellent SPDIF capability with very cheap 108price (yes, that's the reason I bought the card :) 109 110The SPDIF playback and capture are done via the third PCM device 111(hw:0,2). Usually this is assigned to the PCM device "spdif". 112The available rates are 44100 and 48000 Hz. 113For playback with aplay, you can run like below: 114 115 % aplay -Dhw:0,2 foo.wav 116 117or 118 119 % aplay -Dspdif foo.wav 120 12124bit format is also supported experimentally. 122 123The playback and capture over SPDIF use normal DAC and ADC, 124respectively, so you cannot playback both analog and digital streams 125simultaneously. 126 127To enable SPDIF output, you need to turn on "IEC958 Output Switch" 128control via mixer or alsactl ("IEC958" is the official name of 129so-called S/PDIF). Then you'll see the red light on from the card so 130you know that's working obviously :) 131The SPDIF input is always enabled, so you can hear SPDIF input data 132from line-out with "IEC958 In Monitor" switch at any time (see 133below). 134 135You can play via SPDIF even with the first device (hw:0,0), 136but SPDIF is enabled only when the proper format (S16LE), sample rate 137(441100 or 48000) and channels (2) are used. Otherwise it's turned 138off. (Also don't forget to turn on "IEC958 Output Switch", too.) 139 140 141Additionally there are relevant control switches: 142 143"IEC958 Mix Analog" - Mix analog PCM playback and FM-OPL/3 streams and 144 output through SPDIF. This switch appears only on old chip 145 models (CM8738 033 and 037). 146 Note: without this control you can output PCM to SPDIF. 147 This is "mixing" of streams, so e.g. it's not for AC3 output 148 (see the next section). 149 150"IEC958 In Select" - Select SPDIF input, the internal CD-in (false) 151 and the external input (true). 152 153"IEC958 Loop" - SPDIF input data is loop back into SPDIF 154 output (aka bypass) 155 156"IEC958 Copyright" - Set the copyright bit. 157 158"IEC958 5V" - Select 0.5V (coax) or 5V (optical) interface. 159 On some cards this doesn't work and you need to change the 160 configuration with hardware dip-switch. 161 162"IEC958 In Monitor" - SPDIF input is routed to DAC. 163 164"IEC958 In Phase Inverse" - Set SPDIF input format as inverse. 165 [FIXME: this doesn't work on all chips..] 166 167"IEC958 In Valid" - Set input validity flag detection. 168 169Note: When "PCM Playback Switch" is on, you'll hear the digital output 170stream through analog line-out. 171 172 173The AC3 (RAW DIGITAL) OUTPUT 174---------------------------- 175 176The driver supports raw digital (typically AC3) i/o over SPDIF. This 177can be toggled via IEC958 playback control, but usually you need to 178access it via alsa-lib. See alsa-lib documents for more details. 179 180On the raw digital mode, the "PCM Playback Switch" is automatically 181turned off so that non-audio data is heard from the analog line-out. 182Similarly the following switches are off: "IEC958 Mix Analog" and 183"IEC958 Loop". The switches are resumed after closing the SPDIF PCM 184device automatically to the previous state. 185 186On the model 033, AC3 is implemented by the software conversion in 187the alsa-lib. If you need to bypass the software conversion of IEC958 188subframes, pass the "soft_ac3=0" module option. This doesn't matter 189on the newer models. 190 191 192ANALOG MIXER INTERFACE 193---------------------- 194 195The mixer interface on CM8x38 is similar to SB16. 196There are Master, PCM, Synth, CD, Line, Mic and PC Speaker playback 197volumes. Synth, CD, Line and Mic have playback and capture switches, 198too, as well as SB16. 199 200In addition to the standard SB mixer, CM8x38 provides more functions. 201- PCM playback switch 202- PCM capture switch (to capture the data sent to DAC) 203- Mic Boost switch 204- Mic capture volume 205- Aux playback volume/switch and capture switch 206- 3D control switch 207 208 209MIDI CONTROLLER 210--------------- 211 212With CMI8338 chips, the MPU401-UART interface is disabled as default. 213You need to set the module option "mpu_port" to a valid I/O port address 214to enable MIDI support. Valid I/O ports are 0x300, 0x310, 0x320 and 2150x330. Choose a value that doesn't conflict with other cards. 216 217With CMI8738 and newer chips, the MIDI interface is enabled by default 218and the driver automatically chooses a port address. 219 220There is _no_ hardware wavetable function on this chip (except for 221OPL3 synth below). 222What's said as MIDI synth on Windows is a software synthesizer 223emulation. On Linux use TiMidity or other softsynth program for 224playing MIDI music. 225 226 227FM OPL/3 Synth 228-------------- 229 230The FM OPL/3 is also enabled as default only for the first card. 231Set "fm_port" module option for more cards. 232 233The output quality of FM OPL/3 is, however, very weird. 234I don't know why.. 235 236CMI8768 and newer chips do not have the FM synth. 237 238 239Joystick and Modem 240------------------ 241 242The legacy joystick is supported. To enable the joystick support, pass 243joystick_port=1 module option. The value 1 means the auto-detection. 244If the auto-detection fails, try to pass the exact I/O address. 245 246The modem is enabled dynamically via a card control switch "Modem". 247 248 249Debugging Information 250--------------------- 251 252The registers are shown in /proc/asound/cardX/cmipci. If you have any 253problem (especially unexpected behavior of mixer), please attach the 254output of this proc file together with the bug report. 255