[alsa-devel] DSD over HDMI: audio data packetization

[Yang, Libin]

Hi Xuebing,


> -----Original Message-----
> From: Anssi Hannula [mailto:anssi.hannula at iki.fi]
> Sent: Wednesday, December 31, 2014 9:41 PM
> To: Xuebing Wang
> Cc: alsa-devel at alsa-project.org; Yang, Libin; Lin, Mengdong; ; Takashi Iwai; ;
> Wu Fengguang
> Subject: Re: [alsa-devel] DSD over HDMI: audio data packetization
> 
> 31.12.2014, 15:32, Xuebing Wang kirjoitti:
> > Hi Community,
> 
> Hi,
> 
> > I am trying to implement DSD (one bit audio) over HDMI, for Intel
> > integrated graphics. I am referencing HDMI specification 1.3a.
> >
> > Regarding audio data packetization, I am referencing spec:
> > 5.3.4 Audio Sample Packet
> > 7.6 Audio Data Packetization
> >
> > Q1) Would you please point to me where is the source code to handle
> > L-PCM audio sample packetization (to implement 5.3.4 Audio Sample
> > Packet)?
> 
> It is done by the hardware.
> 
> > Q2) I admit that I did not carefully read HD-Audio specification. Is
> > this possible that this L-PCM audio data packetization is done by
> > *hardware* (e.g HDMI related widgets/pins)?
> 
> Yes.
> 
> > Q3) Did we implement "7.2 Audio Sample Clock Capture and Regeneration"?
> 
> That is done by hardware. With some HDA codecs the video driver calculates
> the N/CTS values "manually", but AFAIK not on Intel HW.

As the N/CTS need fs and frequency of TMDS info, the hdmi driver does not
implement this feature.

We currently are designing an audio link between audio subsystem and other 
components, like video or USB.

Maybe we will add the N/CTS information transmission. So we can calculate
the N/CTS value in audio or gfx driver.


> 
> > Thanks.
> > Xuebing Wang
> >
> >
> 
> 
> --
> Anssi Hannula