From: Clemens Ladisch <clemens@ladisch.de>
To: Sergej Sawazki <ce3a@gmx.de>, alsa-devel@alsa-project.org
Subject: Re: ASoC: How to declare volume TLV dB scale?
Date: Fri, 12 Jun 2015 21:47:46 +0200 [thread overview]
Message-ID: <557B3762.20603@ladisch.de> (raw)
In-Reply-To: <557B3260.30001@gmx.de>
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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next prev parent reply other threads:[~2015-06-12 19:48 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-06-12 12:02 ASoC: How to declare volume TLV dB scale? Sergej Sawazki
2015-06-12 16:28 ` Clemens Ladisch
2015-06-12 19:26 ` Sergej Sawazki
2015-06-12 19:47 ` Clemens Ladisch [this message]
2015-06-13 7:15 ` Takashi Iwai
2015-06-13 10:10 ` Sergej Sawazki
2015-06-13 10:29 ` Clemens Ladisch
2015-06-13 10:45 ` Sergej Sawazki
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