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