IEC61937/SPDIF

IEC61937/SPDIF

[ajay khandelwal]

Hi All,
 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
2) Is their any plugin available for IEC61937, I could see only for IEC958
3) Who should create burst preamble, some plug in or driver.

Thanks and Regards,
Ajay

Re: IEC61937/SPDIF

[Anssi Hannula]

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.

-- 
Anssi Hannula

Re: 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