Re: Volume per voices [Feature Request]

[Raymond <rayau@netvigator.com>]

Takashi Iwai wrote:
> At Mon, 01 Aug 2005 00:37:26 +0800,
> Raymond wrote:
> 
>>Jaroslav Kysela wrote:
>>
>>>On Thu, 28 Jul 2005, Raymond wrote:
>>>
>>>
>>>
>>>>In theory, and sound cards with hardware mixing can support this kind of
>>>>volume control.
>>>>
>>>
>>>Nope. Please, define the controls at the driver initialization phase and 
>>>make them inactive when the stream is not open. See emu10k1 or trident 
>>>driver for hints. You must also map the voice volume with substream 
>>>number.
>>>
>>
>>Beside volume control, Is it feasible to bind other controls (e.g.
>>Interaural Time Difference, Interaural Level Difference and SAMPLE RATE 
>>CONVERTOR - Doppler Effect ) to the substream ?
> 
> 
> I think yes.  Whatever directly bound to a PCM substream should be
> handled as IFACE_PCM with a certain subdevice number.
> 
> 
> 
>>How can the alsa application access those controls
>>(SNDRV_CTL_ELEM_IFACE_PCM) using the handle return by snd_pcm_open() ?
> 
> 
> By defining a new API for that purpose :)
> 
> 
> Takashi
> 
> 

Can this kind of volume control with iface = SNDRV_CTL_ELEM_IFACE_PCM
used by mixer application (e.g. alsamixer) or only the application which
open the PCM substream ?

Distortion occur when the combined gain of audio data, hardware mixer ,
equalizer and 3D effect > 6dB ( limit by the 18-bits DAC in AC97 codec)

Can negative number can be used in the kcontrol with type
SNDRV_CTL_ELEM_TYPE_INTEGER ? (i.e. uinfo->value.integer.min < 0 )

What is the maximum value can be assigned to uinfo->value.integer.max ?

In the ALSA au88x0 driver, the hardware mixer provide default gain of
6dB ( 16-bits auido data to 18-bits DAC in AC97 codec ) for the
left/right channels of au8820 and the rear channels of au8810/au8830 (to 
SDAC of quad codec),

For the front channels of au8810/au8830, zero gain in hardware mixer and
this 6dB gain is most likely controlled by the equalizer or 3D effect.

Is there any faster method to find the substream of the subdevice in
snd_vortex_adb_pcm_vol_put ?

struct snd_vortex {

...
	snd_kcontrol_t *ctl_pcm_vol[NR_ADB];
	int mixin[NR_ADB][4];		/* MIXIN */
         int pcm_vol[NR_ADB][4];         /* PCM VOLUME */
...

}

static int snd_vortex_adb_pcm_vol_info(snd_kcontrol_t *kcontrol,
snd_ctl_elem_info_t * uinfo)
{
	vortex_t *vortex = snd_kcontrol_chip(kcontrol);
	uinfo->type = SNDRV_CTL_ELEM_TYPE_INTEGER;
	uinfo->count = (VORTEX_IS_QUAD(vortex) ? 4 : 2);
	uinfo->value.integer.min = 0;
	uinfo->value.integer.max = 255;
	return 0;
}

static int snd_vortex_adb_pcm_change_vol(vortex_t *vortex,int mixin,int
mix,int volume)
{
	if ( volume >= 128 )
		vortex_mix_setinputvolumebyte(vortex, mix, mixin, volume-128);    // GAIN
GAIN
	else
		vortex_mix_setinputvolumebyte(vortex, mix, mixin, volume+128);    // ATTEN
ATTEN
	return 0;
}

static int snd_vortex_adb_pcm_vol_get(snd_kcontrol_t * kcontrol,
snd_ctl_elem_value_t * ucontrol)
{
	int i,subdevice;
	vortex_t *vortex = snd_kcontrol_chip(kcontrol);
	subdevice = kcontrol->id.subdevice;
	for (i=0; i<(VORTEX_IS_QUAD(vortex) ? 4 : 2 ); i++)
		ucontrol->value.integer.value[i] = vortex->pcm_vol[subdevice][i];	
	return 0;
}

static int snd_vortex_adb_pcm_vol_put(snd_kcontrol_t * kcontrol,
snd_ctl_elem_value_t * ucontrol)
{
	int i,j,changed,subdevice;
	vortex_t *vortex = snd_kcontrol_chip(kcontrol);
	subdevice=kcontrol->id.subdevice;
	changed = 0;
	if ( ( kcontrol->vd[0].access & SNDRV_CTL_ELEM_ACCESS_INACTIVE ) == 0 ) {
		for (i=0; i<NR_ADB; i++) {
			if ( vortex->dma_adb[i].substream != NULL ) {
				if ( vortex->dma_adb[i].substream->number == subdevice ) {
					for (j=0; j<(VORTEX_IS_QUAD(vortex) ? 4 : 2 ); j++) {
						if ( vortex->pcm_vol[subdevice][j] !=
ucontrol->value.integer.value[j] )
							changed=1;
						vortex->pcm_vol[subdevice][j] = ucontrol->value.integer.value[j];
					};
					switch(vortex->dma_adb[i].nr_ch) {
					case 1:
						for (j=0; j<(VORTEX_IS_QUAD(vortex) ? 4 : 2 ); j++) {
							snd_vortex_adb_pcm_change_vol(vortex,
vortex->mixin[subdevice][0], vortex->mixplayb[j],
vortex->pcm_vol[subdevice][j]);
						};
						break;
					case 2:
						for (j=0; j<2; j++) {
							snd_vortex_adb_pcm_change_vol(vortex,
vortex->mixin[subdevice][j], vortex->mixplayb[j],
vortex->pcm_vol[subdevice][j]);
							if (VORTEX_IS_QUAD(vortex))
								snd_vortex_adb_pcm_change_vol(vortex,
vortex->mixin[subdevice][j], vortex->mixplayb[j+2],
vortex->pcm_vol[subdevice][j+2]);
						};
						break;
					case 4:
						for (j=0; j<4; j++) {
							snd_vortex_adb_pcm_change_vol(vortex,
vortex->mixin[subdevice][j], vortex->mixplayb[j],
vortex->pcm_vol[subdevice][j]);
						};
						break;
					};
					return changed;
				};
			};
		};
	};
	return changed;
}

static snd_kcontrol_new_t snd_vortex_adb_pcm_vol = {
	.iface =	SNDRV_CTL_ELEM_IFACE_PCM,
	.name =		"ADB PCM Volume",
	.access = 	SNDRV_CTL_ELEM_ACCESS_READWRITE |
SNDRV_CTL_ELEM_ACCESS_INACTIVE,
	.info =		snd_vortex_adb_pcm_vol_info,
	.get =		snd_vortex_adb_pcm_vol_get,
	.put =		snd_vortex_adb_pcm_vol_put,
};


Do we need to make the front and rear channels of au8810/au8830 with
equal default gain and equal volume range ? e.g. Adding mixer between
equalizer and AC97 and a switch to allow each substream to bypass
equalizer, the other way is to set equalizer in bypass mode for all
substreams.


au8810/au8830
                                    (6db)
Front channels          +----------MIXER-------------+
                         |                            |
                         |(0dB)     (6dB)       (0dB) |
    DMA -> FIFO -> SRC -> MIXER -> Equalizer -> MIXER -> AC97
                |           |
                |           +--------------------------> SPDIF
                |
Rear channels  +--SRC -----------> MIXER -------------> SDAC
                                    (6dB)




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