[alsa-devel] ASOC and 12 bit volume control
broonie at opensource.wolfsonmicro.com
Sun Jul 20 21:19:03 CEST 2008
On Sun, Jul 20, 2008 at 02:47:31PM -0400, Jon Smirl wrote:
> On 7/20/08, Mark Brown <broonie at opensource.wolfsonmicro.com> wrote:
> > also possible that the combination of large registers and high
> > resolution fields within them may mean that special treatment is
> > warranted in order to avoid blocking user applications too much with
> > high volume register writes, but I'm not sure if that's a real issue or
> > not.
> These chips are capable of processing 192K 24b HD quality audio.
> Datasheet http://www.ti.com/lit/gpn/tas5504
> Do the Intel HD audio chips have similar controls?
A brief look suggests that there's nothing over 32 bits in the register
> I believe the TI codecs are implemented with a combination of an 8051
> core controlling a DSP. The i2c interface is talking to the 8051
> core, not real hardware registers. The 8051 takes the incoming i2c
> messages and stores them in RAM and uses the info to manipulate the
The issue is the time taken to do the I/O via the I2C bus, not the
implementation in the chip - if anything I'd expect this to be slower
than a direct hardware implementation but not perceptibly. If
applications try to step through all the values for a control with
anything approaching the available resolution then that'd be a lot of
data being written. Like I say, it may not be a practical issue (I'd
expect applications to be smarter) but it raised my eyebrows.
> > Are any of these 28 bit controls not in 32 byte registers?
> 0x49-0x50, bass management
> 4 bytes, contain 5.23 coefficients
> The chip supports DRC (compression and expansion), some of the DRC
> parameters are 48bits in 25.23 format. Loudness is 25.23 too.
> 0x92 and 0x94 are examples of 64 bit registers.
OK, so the bass management looks like it should be able to fit in a
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