[mythtv] Digital audio passthrough

[Jean-Yves Avenard]

Hi

On 14 September 2010 18:01, James Courtier-Dutton
<james.dutton at gmail.com> wrote:

> I am an ALSA developer.
> From your description of how myth works, I am amazed that AC3
> passthrough ever worked.
> The "device" open will override any mixer controls, so the iecset will
> be forgotten once you open the device.

The iecset was introduced for 0.23

It does work for most by the look of things, this is the first case we
found that it didn't work.

Earlier on, it didn't work for some, because we also had to set the
:"copyright" flag (0x4)  and not just the iec one (0x2).
Since setting both flags, it's been working fine...

You can tell by the amount of people using digital passthrough, and
surely we would have heard about it sooner.

>
> The correct way to do AC3 passthrough is by opening the device with
> the device name:
> iec958:AES0=0x6,AES1=0x82,AES2=0x0,AES3=0x2
> and not using any "iecset" utility.
>
> This is how xine does it, and it has always worked. I wrote the source
> code in xine to do it.
> When switching from non-audio to PCM, one has to close and open the
> device again.

And this is also a much easier way to do it !!