[alsa-devel] ICT Bits for HDMI HBR feature

[Takashi Iwai]

At Mon, 13 Aug 2012 16:08:43 +0800,
Wang Xingchao wrote:
> 
> Hi Takashi,
> 
> 2012/8/7 Takashi Iwai <tiwai at suse.de>:
> > At Tue, 7 Aug 2012 08:09:26 +0000,
> > Wang, Xingchao wrote:
> >>
> >> Hi Takashi,
> >>
> >> Should we set ICT bits when enable HDMI HBR features? Here's quote from HDA Specification Rev1.0a(page 150).
> >> "
> >> ICT[3:0] (IEC Coding Type): Programmed according to IEC standards to enable stream types for High Bit Rate Encoding. This is valid only for HDMI and Display port digital Pin Widgets.
> >> "
> >> Since HDMI HBR already works on some chips, I wonder if they set the bits correctly.
> >
> > I can't find the specification right now, so I also don't know what
> > value should be put there.  But I thought it's expected to be zero.
> > Maybe it's my old memory.
> >
> > So, if you find anything about it, let me know.
> >
> 
> Besides ICT bits setting, i found CC[Category Code] was not used either.

It's set via normal IEC958 control.  The second byte corresponds to
DIG2.

For example, you should be able to change it via iecset utility.
Or passing the right AES2=xx argument to iec958 PCM type.

	% iecset -c1 category 0x02

> Here's the  description for "Category code" from IEC Standard spec:
> 
> "Channel status including the category code is defined in IEC 60958-3
> for consumer
> applications; these category codes are used for other variations of
> the IEC 60958 series for
> consumer use, such as the IEC 61937 series."
> 
> Do you have idea about how to use it and is it useful for the HBR issue?

This is purely an issue of receiver, how tolerant it is, I think.


Takashi