[mythtv-users] SPDIF passthrough problems / VDPAU problems

[Jean-Yves Avenard]

On 31 January 2012 22:29,  <mythtv at thestack.de> wrote:
> Hi,
>
> for the audio problems:
>
> My HTPC running mythtv 0.24.1 (now upgraded to 0.24.2) is connected to
> an AVR via optical SPDIF. Here's my audio settings:
>
> - Audio output device: "ALSA:hw:CARD=CMI8738,DEV=2" (also tried
> "ALSA:iec958:CARD=CMI8738,DEV=0" here)

this is not a valid device, and not one you want to use.

> - DD and DTS checked in capabilities
> - Speaker configuration: 5.1
> - Upmixing disabled
> - Advanced Audio Config:

What is it with people touching advanced audio config...

>  - Digital output device: ALSA:iec958:{ AES0 0x02 } (also tried without
> this enabled)

leave the advanced settings untouched, everything should be unchecked

Read the wiki and the documentation.

You have a Scan Audio Device button, press it then select an audio
device that it found.

If using SPDIF, it will have iec958 in its name


>
> - Internal mixer disabled
>
> All kind of two channel audio works fine but for multichannel audio
> (both DD/AC3 and DTS) I only get choppy output. Changing Speaker config
> to Stereo or disabling the digital audio device / advanced settings
> doesn't help oder I even get no sound at all.

you must select 5.1 in the speaker config and have AC3 and DTS checked...

Forget any ancient documentations that would have stated that for
digital passthrough you would have to use stereo. Those documentation
are obsolete and it hasn't been the case for years.

> In VLC media player and mplayer the same media files are working
> perfectly. I thought the "reenc 0" in the logs means everything is right
> but it seems it's not.

what audio device are you using in VLC or mplayer? the same audio
device will work in myth in the same fashion

> ALSA lib pcm_dmix.c:1018:(snd_pcm_dmix_open) unable to open slave
> 2012-01-30 12:05:19.018 ALSA, Error:
> snd_pcm_open("dmix:CARD=CX8811,DEV=0"): No such file or directory
> ALSA lib pcm_dsnoop.c:551:(snd_pcm_dsnoop_open) The dsnoop plugin
> supports only capture stream
[snip]

you should never see those messages when starting a playback.
Only when you have enabled audio log and are scanning for audio
devices, it goes through all the ones found by ALSA, and myth filters
them as required

> 2012-01-30 12:12:20.150 AO: Opening audio device
> 'hw:CARD=CMI8738,DEV=2' ch 2(6) sr 48000 sf signed 16 bit reenc 0
> 2012-01-30 12:12:20.152 ALSA, Error: Setting hardware audio buffer size
> to 128
> 2012-01-30 12:12:20.152 ALSA, Error: Error opening
> /proc/asound/card0/pcm2p/sub0/prealloc: Permission denied.
> 2012-01-30 12:12:20.152 ALSA, Error: Try to manually increase audio
> buffer with: echo 128 | sudo tee /proc/asound/card0/pcm2p/sub0/prealloc

Well, here would be a useful hint to start with on what you have to do


> 2012-01-30 12:12:20.152 ALSA, Error: Unable to sufficiently increase
> ALSA hardware buffer size - underruns are likely

>
> The last line then gets repeated VERY often (about 25 times per second,
> maybe that's one line for each frame?)

well, you have an issue in your video file here and myth is unable to
decode it with VDPAU
>

> Manually increasing audio buffer with: echo 128 | sudo tee
> /proc/asound/card0/pcm2p/sub0/prealloc didn't help.

the issue you have reported so far is an issue with the media being
played, not your audio config (even though this one needs adjusting)