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Diffstat (limited to 'Documentation/sound/oss')
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diff --git a/Documentation/sound/oss/vwsnd b/Documentation/sound/oss/vwsnd deleted file mode 100644 index 4c6cbdb3c548..000000000000 --- a/Documentation/sound/oss/vwsnd +++ /dev/null @@ -1,293 +0,0 @@ -vwsnd - Sound driver for the Silicon Graphics 320 and 540 Visual -Workstations' onboard audio. - -Copyright 1999 Silicon Graphics, Inc. All rights reserved. - - -At the time of this writing, March 1999, there are two models of -Visual Workstation, the 320 and the 540. This document only describes -those models. Future Visual Workstation models may have different -sound capabilities, and this driver will probably not work on those -boxes. - -The Visual Workstation has an Analog Devices AD1843 "SoundComm" audio -codec chip. The AD1843 is accessed through the Cobalt I/O ASIC, also -known as Lithium. This driver programs both chips. - -============================================================================== -QUICK CONFIGURATION - - # insmod soundcore - # insmod vwsnd - -============================================================================== -I/O CONNECTIONS - -On the Visual Workstation, only three of the AD1843 inputs are hooked -up. The analog line in jacks are connected to the AD1843's AUX1 -input. The CD audio lines are connected to the AD1843's AUX2 input. -The microphone jack is connected to the AD1843's MIC input. The mic -jack is mono, but the signal is delivered to both the left and right -MIC inputs. You can record in stereo from the mic input, but you will -get the same signal on both channels (within the limits of A/D -accuracy). Full scale on the Line input is +/- 2.0 V. Full scale on -the MIC input is 20 dB less, or +/- 0.2 V. - -The AD1843's LOUT1 outputs are connected to the Line Out jacks. The -AD1843's HPOUT outputs are connected to the speaker/headphone jack. -LOUT2 is not connected. Line out's maximum level is +/- 2.0 V peak to -peak. The speaker/headphone out's maximum is +/- 4.0 V peak to peak. - -The AD1843's PCM input channel and one of its output channels (DAC1) -are connected to Lithium. The other output channel (DAC2) is not -connected. - -============================================================================== -CAPABILITIES - -The AD1843 has PCM input and output (Pulse Code Modulation, also known -as wavetable). PCM input and output can be mono or stereo in any of -four formats. The formats are 16 bit signed and 8 bit unsigned, -u-Law, and A-Law format. Any sample rate from 4 KHz to 49 KHz is -available, in 1 Hz increments. - -The AD1843 includes an analog mixer that can mix all three input -signals (line, mic and CD) into the analog outputs. The mixer has a -separate gain control and mute switch for each input. - -There are two outputs, line out and speaker/headphone out. They -always produce the same signal, and the speaker always has 3 dB more -gain than the line out. The speaker/headphone output can be muted, -but this driver does not export that function. - -The hardware can sync audio to the video clock, but this driver does -not have a way to specify syncing to video. - -============================================================================== -PROGRAMMING - -This section explains the API supported by the driver. Also see the -Open Sound Programming Guide at http://www.opensound.com/pguide/ . -This section assumes familiarity with that document. - -The driver has two interfaces, an I/O interface and a mixer interface. -There is no MIDI or sequencer capability. - -============================================================================== -PROGRAMMING PCM I/O - -The I/O interface is usually accessed as /dev/audio or /dev/dsp. -Using the standard Open Sound System (OSS) ioctl calls, the sample -rate, number of channels, and sample format may be set within the -limitations described above. The driver supports triggering. It also -supports getting the input and output pointers with one-sample -accuracy. - -The SNDCTL_DSP_GETCAP ioctl returns these capabilities. - - DSP_CAP_DUPLEX - driver supports full duplex. - - DSP_CAP_TRIGGER - driver supports triggering. - - DSP_CAP_REALTIME - values returned by SNDCTL_DSP_GETIPTR - and SNDCTL_DSP_GETOPTR are accurate to a few samples. - -Memory mapping (mmap) is not implemented. - -The driver permits subdivided fragment sizes from 64 to 4096 bytes. -The number of fragments can be anything from 3 fragments to however -many fragments fit into 124 kilobytes. It is up to the user to -determine how few/small fragments can be used without introducing -glitches with a given workload. Linux is not realtime, so we can't -promise anything. (sigh...) - -When this driver is switched into or out of mu-Law or A-Law mode on -output, it may produce an audible click. This is unavoidable. To -prevent clicking, use signed 16-bit mode instead, and convert from -mu-Law or A-Law format in software. - -============================================================================== -PROGRAMMING THE MIXER INTERFACE - -The mixer interface is usually accessed as /dev/mixer. It is accessed -through ioctls. The mixer allows the application to control gain or -mute several audio signal paths, and also allows selection of the -recording source. - -Each of the constants described here can be read using the -MIXER_READ(SOUND_MIXER_xxx) ioctl. Those that are not read-only can -also be written using the MIXER_WRITE(SOUND_MIXER_xxx) ioctl. In most -cases, <sys/soundcard.h> defines constants SOUND_MIXER_READ_xxx and -SOUND_MIXER_WRITE_xxx which work just as well. - -SOUND_MIXER_CAPS Read-only - -This is a mask of optional driver capabilities that are implemented. -This driver's only capability is SOUND_CAP_EXCL_INPUT, which means -that only one recording source can be active at a time. - -SOUND_MIXER_DEVMASK Read-only - -This is a mask of the sound channels. This driver's channels are PCM, -LINE, MIC, CD, and RECLEV. - -SOUND_MIXER_STEREODEVS Read-only - -This is a mask of which sound channels are capable of stereo. All -channels are capable of stereo. (But see caveat on MIC input in I/O -CONNECTIONS section above). - -SOUND_MIXER_OUTMASK Read-only - -This is a mask of channels that route inputs through to outputs. -Those are LINE, MIC, and CD. - -SOUND_MIXER_RECMASK Read-only - -This is a mask of channels that can be recording sources. Those are -PCM, LINE, MIC, CD. - -SOUND_MIXER_PCM Default: 0x5757 (0 dB) - -This is the gain control for PCM output. The left and right channel -gain are controlled independently. This gain control has 64 levels, -which range from -82.5 dB to +12.0 dB in 1.5 dB steps. Those 64 -levels are mapped onto 100 levels at the ioctl, see below. - -SOUND_MIXER_LINE Default: 0x4a4a (0 dB) - -This is the gain control for mixing the Line In source into the -outputs. The left and right channel gain are controlled -independently. This gain control has 32 levels, which range from --34.5 dB to +12.0 dB in 1.5 dB steps. Those 32 levels are mapped onto -100 levels at the ioctl, see below. - -SOUND_MIXER_MIC Default: 0x4a4a (0 dB) - -This is the gain control for mixing the MIC source into the outputs. -The left and right channel gain are controlled independently. This -gain control has 32 levels, which range from -34.5 dB to +12.0 dB in -1.5 dB steps. Those 32 levels are mapped onto 100 levels at the -ioctl, see below. - -SOUND_MIXER_CD Default: 0x4a4a (0 dB) - -This is the gain control for mixing the CD audio source into the -outputs. The left and right channel gain are controlled -independently. This gain control has 32 levels, which range from --34.5 dB to +12.0 dB in 1.5 dB steps. Those 32 levels are mapped onto -100 levels at the ioctl, see below. - -SOUND_MIXER_RECLEV Default: 0 (0 dB) - -This is the gain control for PCM input (RECording LEVel). The left -and right channel gain are controlled independently. This gain -control has 16 levels, which range from 0 dB to +22.5 dB in 1.5 dB -steps. Those 16 levels are mapped onto 100 levels at the ioctl, see -below. - -SOUND_MIXER_RECSRC Default: SOUND_MASK_LINE - -This is a mask of currently selected PCM input sources (RECording -SouRCes). Because the AD1843 can only have a single recording source -at a time, only one bit at a time can be set in this mask. The -allowable values are SOUND_MASK_PCM, SOUND_MASK_LINE, SOUND_MASK_MIC, -or SOUND_MASK_CD. Selecting SOUND_MASK_PCM sets up internal -resampling which is useful for loopback testing and for hardware -sample rate conversion. But software sample rate conversion is -probably faster, so I don't know how useful that is. - -SOUND_MIXER_OUTSRC DEFAULT: SOUND_MASK_LINE|SOUND_MASK_MIC|SOUND_MASK_CD - -This is a mask of sources that are currently passed through to the -outputs. Those sources whose bits are not set are muted. - -============================================================================== -GAIN CONTROL - -There are five gain controls listed above. Each has 16, 32, or 64 -steps. Each control has 1.5 dB of gain per step. Each control is -stereo. - -The OSS defines the argument to a channel gain ioctl as having two -components, left and right, each of which ranges from 0 to 100. The -two components are packed into the same word, with the left side gain -in the least significant byte, and the right side gain in the second -least significant byte. In C, we would say this. - - #include <assert.h> - - ... - - assert(leftgain >= 0 && leftgain <= 100); - assert(rightgain >= 0 && rightgain <= 100); - arg = leftgain | rightgain << 8; - -So each OSS gain control has 101 steps. But the hardware has 16, 32, -or 64 steps. The hardware steps are spread across the 101 OSS steps -nearly evenly. The conversion formulas are like this, given N equals -16, 32, or 64. - - int round = N/2 - 1; - OSS_gain_steps = (hw_gain_steps * 100 + round) / (N - 1); - hw_gain_steps = (OSS_gain_steps * (N - 1) + round) / 100; - -Here is a snippet of C code that will return the left and right gain -of any channel in dB. Pass it one of the predefined gain_desc_t -structures to access any of the five channels' gains. - - typedef struct gain_desc { - float min_gain; - float gain_step; - int nbits; - int chan; - } gain_desc_t; - - const gain_desc_t gain_pcm = { -82.5, 1.5, 6, SOUND_MIXER_PCM }; - const gain_desc_t gain_line = { -34.5, 1.5, 5, SOUND_MIXER_LINE }; - const gain_desc_t gain_mic = { -34.5, 1.5, 5, SOUND_MIXER_MIC }; - const gain_desc_t gain_cd = { -34.5, 1.5, 5, SOUND_MIXER_CD }; - const gain_desc_t gain_reclev = { 0.0, 1.5, 4, SOUND_MIXER_RECLEV }; - - int get_gain_dB(int fd, const gain_desc_t *gp, - float *left, float *right) - { - int word; - int lg, rg; - int mask = (1 << gp->nbits) - 1; - - if (ioctl(fd, MIXER_READ(gp->chan), &word) != 0) - return -1; /* fail */ - lg = word & 0xFF; - rg = word >> 8 & 0xFF; - lg = (lg * mask + mask / 2) / 100; - rg = (rg * mask + mask / 2) / 100; - *left = gp->min_gain + gp->gain_step * lg; - *right = gp->min_gain + gp->gain_step * rg; - return 0; - } - -And here is the corresponding routine to set a channel's gain in dB. - - int set_gain_dB(int fd, const gain_desc_t *gp, float left, float right) - { - float max_gain = - gp->min_gain + (1 << gp->nbits) * gp->gain_step; - float round = gp->gain_step / 2; - int mask = (1 << gp->nbits) - 1; - int word; - int lg, rg; - - if (left < gp->min_gain || right < gp->min_gain) - return EINVAL; - lg = (left - gp->min_gain + round) / gp->gain_step; - rg = (right - gp->min_gain + round) / gp->gain_step; - if (lg >= (1 << gp->nbits) || rg >= (1 << gp->nbits)) - return EINVAL; - lg = (100 * lg + mask / 2) / mask; - rg = (100 * rg + mask / 2) / mask; - word = lg | rg << 8; - - return ioctl(fd, MIXER_WRITE(gp->chan), &word); - } - |