ASoC: How to declare volume TLV dB scale?

ASoC: How to declare volume TLV dB scale?

[Sergej Sawazki]

Dear all,
 
could someone please help me to understand the mixer controls TLV scale?
What would be the DECLARE_TLV_DB_SCALE values for the following example?
 
reg. value:  0    ..  0x3ff
phys. value: 0dB  .. -128dB
volume:      100% ..  0%(mute)

What does TLV actually stand for?

Many thanks in advance,
Sergej Sawazki
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Re: ASoC: How to declare volume TLV dB scale?

[Clemens Ladisch]

Sergej Sawazki wrote:
> could someone please help me to understand the mixer controls TLV scale?
> What would be the DECLARE_TLV_DB_SCALE values for the following example?
>
> reg. value:  0    ..  0x3ff
> phys. value: 0dB  .. -128dB
> volume:      100% ..  0%(mute)

0% volume would be -∞ dB.

And how are the register values mapped between the min/max values?
Does 0x200 correspond to -64 dB, or 50 % of the sample value, or
50 % of the volume?

> What does TLV actually stand for?

Type-length-value.  It's an implementation detail.


Regards,
Clemens
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Re: ASoC: How to declare volume TLV dB scale?

[Sergej Sawazki]

On Fri, 12 Jun 2015 18:28:54 +0200, Clemens Ladisch wrote:
> Sergej Sawazki wrote:
>> could someone please help me to understand the mixer controls TLV scale?
>> What would be the DECLARE_TLV_DB_SCALE values for the following example?
>>
>> reg. value:  0    ..  0x3ff
>> phys. value: 0dB  .. -128dB
>> volume:      100% ..  0%(mute)
>
> 0% volume would be -∞ dB.
>
> And how are the register values mapped between the min/max values?
> Does 0x200 correspond to -64 dB, or 50 % of the sample value, or
> 50 % of the volume?
>

The output of the DAC can be attenuated in 0.125dB steps, so 0x200
would be -64dB.

register value | attenuation level (dB) | volume (%)
---------------+------------------------+-----------
   0x000        |     0.0                |  100
   0x001        |    -0.125              |
    ...         |    ...                 |  ...
   0x200        |   -64.0                |
    ...         |    ...                 |  ...
   0x3fe        |  -127.75               |
   0x3ff        |    -∞ (mute)           |    0

Thanks,
Sergej
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Re: ASoC: How to declare volume TLV dB scale?

[Clemens Ladisch]

Sergej Sawazki wrote:
> On Fri, 12 Jun 2015 18:28:54 +0200, Clemens Ladisch wrote:
>> Sergej Sawazki wrote:
>>> could someone please help me to understand the mixer controls TLV scale?
>>> What would be the DECLARE_TLV_DB_SCALE values for the following example?
>>>
>>> reg. value:  0    ..  0x3ff
>>> phys. value: 0dB  .. -128dB
>>> volume:      100% ..  0%(mute)
>>
>> 0% volume would be -∞ dB.
>>
>> And how are the register values mapped between the min/max values?
>> Does 0x200 correspond to -64 dB, or 50 % of the sample value, or
>> 50 % of the volume?
>
> The output of the DAC can be attenuated in 0.125dB steps, so 0x200
> would be -64dB.
>
> register value | attenuation level (dB) | volume (%)
> ---------------+------------------------+-----------
>   0x000        |     0.0                |  100
>   0x001        |    -0.125              |
>    ...         |    ...                 |  ...
>   0x200        |   -64.0                |
>    ...         |    ...                 |  ...
>   0x3fe        |  -127.75               |
>   0x3ff        |    -∞ (mute)           |    0

0.125 dB is too small for the 0.01 dB resolution of DECLARE_TLV_DB_SCALE,
so you have to use DB_MINMAX instead:  TLV_DB_MINMAX_MUTE_ITEM(-128, 0)


Regards,
Clemens
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Re: ASoC: How to declare volume TLV dB scale?

[Takashi Iwai]

At Fri, 12 Jun 2015 21:47:46 +0200,
Clemens Ladisch wrote:
> 
> Sergej Sawazki wrote:
> > On Fri, 12 Jun 2015 18:28:54 +0200, Clemens Ladisch wrote:
> >> Sergej Sawazki wrote:
> >>> could someone please help me to understand the mixer controls TLV scale?
> >>> What would be the DECLARE_TLV_DB_SCALE values for the following example?
> >>>
> >>> reg. value:  0    ..  0x3ff
> >>> phys. value: 0dB  .. -128dB
> >>> volume:      100% ..  0%(mute)
> >>
> >> 0% volume would be -∞ dB.
> >>
> >> And how are the register values mapped between the min/max values?
> >> Does 0x200 correspond to -64 dB, or 50 % of the sample value, or
> >> 50 % of the volume?
> >
> > The output of the DAC can be attenuated in 0.125dB steps, so 0x200
> > would be -64dB.
> >
> > register value | attenuation level (dB) | volume (%)
> > ---------------+------------------------+-----------
> >   0x000        |     0.0                |  100
> >   0x001        |    -0.125              |
> >    ...         |    ...                 |  ...
> >   0x200        |   -64.0                |
> >    ...         |    ...                 |  ...
> >   0x3fe        |  -127.75               |
> >   0x3ff        |    -∞ (mute)           |    0
> 
> 0.125 dB is too small for the 0.01 dB resolution of DECLARE_TLV_DB_SCALE,
> so you have to use DB_MINMAX instead:  TLV_DB_MINMAX_MUTE_ITEM(-128, 0)

And you need to implement the ctl get/put callback to revert the value
as (0x3ff - raw value).  An decrement value isn't supposed to work.


Takashi
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Re: ASoC: How to declare volume TLV dB scale?

[Sergej Sawazki]

On Sat, 13 Jun 2015 09:15:49 +0200, Takashi Iwai wrote:
> At Fri, 12 Jun 2015 21:47:46 +0200,
> Clemens Ladisch wrote:
>>
>> Sergej Sawazki wrote:
>>>
>>> The output of the DAC can be attenuated in 0.125dB steps, so 0x200
>>> would be -64dB.
>>
>> 0.125 dB is too small for the 0.01 dB resolution of DECLARE_TLV_DB_SCALE,
>> so you have to use DB_MINMAX instead:  TLV_DB_MINMAX_MUTE_ITEM(-128, 0)
>
> And you need to implement the ctl get/put callback to revert the value
> as (0x3ff - raw value).  An decrement value isn't supposed to work.
>

Clemens, Takashi, thanks for your answers.

I am getting the expected dB scaling with:
DECLARE_TLV_DB_MINMAX_MUTE(vol_tlv, -12800, 0)
does it make sense?

Regards,
Sergej

Re: ASoC: How to declare volume TLV dB scale?

[Clemens Ladisch]

Sergej Sawazki wrote:
> On Sat, 13 Jun 2015 09:15:49 +0200, Takashi Iwai wrote:
>> Clemens Ladisch wrote:
>>> 0.125 dB is too small for the 0.01 dB resolution of DECLARE_TLV_DB_SCALE,
>>> so you have to use DB_MINMAX instead:  TLV_DB_MINMAX_MUTE_ITEM(-128, 0)
>>
>> And you need to implement the ctl get/put callback to revert the value
>> as (0x3ff - raw value).  An decrement value isn't supposed to work.

If you're using one of the SOC_xxx_TLV macros, you would set the 'invert'
parameter.

> I am getting the expected dB scaling with:
> DECLARE_TLV_DB_MINMAX_MUTE(vol_tlv, -12800, 0)
> does it make sense?

Yes.  (-128 would have been -1.28 dB.)


Regards,
Clemens

Re: ASoC: How to declare volume TLV dB scale?

[Sergej Sawazki]

On Sat, 13 Jun 2015 12:29:35 +0200, Clemens Ladisch wrote:
> Sergej Sawazki wrote:
>> On Sat, 13 Jun 2015 09:15:49 +0200, Takashi Iwai wrote:

>>> And you need to implement the ctl get/put callback to revert the value
>>> as (0x3ff - raw value).  An decrement value isn't supposed to work.
>
> If you're using one of the SOC_xxx_TLV macros, you would set the 'invert'
> parameter.
>
>> I am getting the expected dB scaling with:
>> DECLARE_TLV_DB_MINMAX_MUTE(vol_tlv, -12800, 0)
>> does it make sense?
>
> Yes.  (-128 would have been -1.28 dB.)
>

Thanks.

Regards,
Sergej