[mythtv-users] .24 Audio results: mixed

[Jean-Yves Avenard]

Hi

On 18 June 2010 15:34, Douglas Peale <Douglas_Peale at comcast.net> wrote:
>
> In .23, I was using Alsa:default 5.1 with digital pass through enabled for Dolby digital and AC3. This was working with the
> exception of always having to toggle the mute button in the mixer app off then on nearly every time I started the myth front end.


but what did you have in your digital passthrough settings, certainly
not ALSA:default.

So choose in the list what is available. don't type it manually,
select the actual device.
If you output via SPDIF, you will have an entry ALSA:iec859
if it's via HDMI, it will be ALSA:hdmi etc..

>
> I tried setting it back to alsa:default, but alsa:default is no longer listed as one of the options. I manually typed in
> alsa:default.
> Oh, this is strange, it is now working. My receiver reports Dolby Digital.
> Tried changing to 7.1, got silence. switched back to 5.1 and still have silence. Brought up the mixer app, toggled the mute
> button off & on and got sound back.

It could be an issue in the alsa driver, the mute buttons is with the
mixer , you are disabling the output and reenable it.

Select 7.1 if you have 7.1 system attached to it, and note that this
is not possible if you output audio via digital other than hdmi

When you select 7.1, you give mythtv a hint of what system you have,
so it knows what kind of upsampling or downsampling will be required.

When actually opening the audio card, the new audio code now actually
queries the audio card to find out how many channels are supported by
that device.
ALSA:default, or spdif , will report 2 channels only as only stereo
PCM can be sent over (AC3 and DTS are sent over a stereo PCM stream).

If you select 7.1, but at run time it sees that your system only
supports stereo and you haven't checked AC3 passthrough, it will only
send out stereo audio.

If you have AC3 and DTS checked, then it will know it needs to encode
the audio out as AC3
>
> I guess I'm back where I was with flaky sound.
>
> I'm going to hold off on the ticket for a bit to see if I can pin down the flakiness a bit.

Showing the output is always going to show what's going on, being
invalid or not , it will help.

I guess I can make the logs a bit more verbose, like if you select
7.1, but your system only reports stereo at run time , I could display
a message in the log..

My original ideas was to actually fill the speaker configuration in
the settings based on what your audio card reports.
Like if the audio output shows stereo only, I display AC3 and DTS, if
you check those, 5.1 is also showed.
If the audio card report 2, 6 and 8, that's what I would show

 But the amount of work required, and my lack of knowledge with the Qt
interface, in particular with dynamic field meant that I left this
idea in the air, hoping that people will select the right config.
Because at the end of the day, you can't know for sure, from the
software point of view, what you have actually connected
The other thing that made it difficult, is that ALSA reports the
number of channels that are supported, not the speaker configurations.
So 4 could be L+F+C+LFE or L+F+RR+RL etc...

Hope that makes sense.