[alsa-devel] IEC61937/SPDIF

[Takashi Iwai]

At Tue, 14 Jun 2011 21:09:43 +0300,
Anssi Hannula wrote:
> 
> On 14.06.2011 15:47, ajay khandelwal wrote:
> > Hi All,
> 
> Hi!
> 
> I've worked with IEC61937, but I'm no ALSA expert, so I hope others
> correct me if I'm wrong.
> 
> >  I have to develop driver for SPDIF output of my board connected to HDMI.
> > 
> > I'm not sure for following (specially IEC61937)
> > 1) How should driver know if it is compressed audio or plain pcm
> 
> You can look at the bit 1 (0x02) of AES0 IEC958 channel status.
> 
> The driver generally provides IEC958 controls:
> http://www.alsa-project.org/~tiwai/writing-an-alsa-driver/ch10s03.html
> That are then used via hooks in "foo.pcm.hdmi.0" (or "foo.pcm.iec958.0"
> for non-hdmi) definition in /usr/share/alsa/cards/foo.conf (look at
> existing drivers for examples).
> Applications can then set these flags by e.g. opening the ALSA audio
> device as "hdmi:AES0=0x06,AES1=0x82" etc.
> 
> > 2) Is their any plugin available for IEC61937, I could see only for IEC958
> 
> No.
> 
> > 3) Who should create burst preamble, some plug in or driver.
> 
> Currently they are created by the applications themselves.

There is also iec958 alsa-lib PCM plugin.  But this is usable only for
drivers that can take IEC958 subframes as the supported format.


Takashi