[mythtv-users] Not the usual problem with digital passthrough.

Thu Feb 28 16:59:18 UTC 2008

On Thu, Feb 28, 2008 at 10:27 AM, Robert Jones <kaosfere at gmail.com> wrote:

> Hi, everyone.
>
> I decided yesterday that I was going to do away with my standalone DVD
> player and allow myth to take over that role in my entertainment
> center.  However, I ran into some bizarre issues getting audio to
> passthrough to my home theater receiver.
>
> I'm currently running Ubuntu Gutsy, tracking the Mythbuntu weekly
> builds of the svn trunk.  My system has MCP51 onboard audio, using the
> hda-intel drivers manually updated to the latest ALSA beta (although
> this also occured with earlier versions).
> I'm pulling digital out via S/PDIF.
>
> My audio out and digital passthrough are both currently set to
> ALSA:iec958.
>
> I can get full dolby digital to my amp using mplayer, by routing sound
> to ALSA:iec958 and forcing hwac3.  However, when I try to play the
> same DVD through myth, the audio I get is raw digital noise.  It's
> almost as though the bitstream is being sent down the wire as plain
> PCM audio.
>
> I have tried jiggering the output devices.  using ALSA:plug:iec958
> doesn't change anything.  Nor do any of the AESx hex incantations that
> I have seen scattered about -- they either break audio entirely, or do
> nothing to change the presentation of raw digital noise.  Accessing
> hw:0,1 doesn't help, either.
>
> (And, yes, I'm set to AC3 and DTS passthrough, and "use video as
> timebase" is off.)
>
> For reference, here's the output of aplay -l:
>
> **** List of PLAYBACK Hardware Devices ****
> card 0: NVidia [HDA NVidia], device 0: AD198x Analog [AD198x Analog]
>  Subdevices: 1/1
>  Subdevice #0: subdevice #0
> card 0: NVidia [HDA NVidia], device 1: AD198x Digital [AD198x Digital]
>  Subdevices: 1/1
>  Subdevice #0: subdevice #0
>
>
>
>
>
> Here's aplay -L:
>
> default:CARD=NVidia
>    HDA NVidia, AD198x Analog
>    Default Audio Device
> front:CARD=NVidia,DEV=0
>    HDA NVidia, AD198x Analog
>    Front speakers
> surround40:CARD=NVidia,DEV=0
>    HDA NVidia, AD198x Analog
>    4.0 Surround output to Front and Rear speakers
> surround41:CARD=NVidia,DEV=0
>    HDA NVidia, AD198x Analog
>    4.1 Surround output to Front, Rear and Subwoofer speakers
> surround50:CARD=NVidia,DEV=0
>    HDA NVidia, AD198x Analog
>    5.0 Surround output to Front, Center and Rear speakers
> surround51:CARD=NVidia,DEV=0
>    HDA NVidia, AD198x Analog
>    5.1 Surround output to Front, Center, Rear and Subwoofer speakers
> surround71:CARD=NVidia,DEV=0
>    HDA NVidia, AD198x Analog
>    7.1 Surround output to Front, Center, Side, Rear and Woofer speakers
> iec958:CARD=NVidia,DEV=0
>    HDA NVidia, AD198x Digital
>    IEC958 (S/PDIF) Digital Audio Output
> null
>    Discard all samples (playback) or generate zero samples (capture)
>
>
>
>
> And here's a portion of my frontend log (from a title screen, so it's
> only 2-channel AC3, but 6-channel looks similar, and both sound the
> same), with -v audio turned on.:
>
>
>
> 2008-02-28 02:45:40.997 AFD: Opened codec 0xaa6ef030, id(AC3) type(Audio)
> 2008-02-28 02:45:40.998 AFD: Audio Track #1 is A/V stream #1 and has 0
> channels in the Undetermined language(7695972).
> 2008-02-28 02:45:41.007 AFD: Selected track 1: Undetermined LIBA52 2ch
> (A/V Stream #1)
> 2008-02-28 02:45:41.008 AFD: Initializing audio parms from audio track #1
> 2008-02-28 02:45:41.008 AFD: Audio format changed digital passthrough
> id( AC3) 48000Hz  2ch  16bps pt
>                        from id(NONE)    -1Hz -1ch   0bps    ;
> id(NONE)    -1Hz -1ch   0bps
>                        to   id( AC3) 48000Hz  2ch  16bps pt ; id(
> AC3) 48000Hz  2ch  16bps pt
> 2008-02-28 02:45:41.019 AO: Needs upmix
> 2008-02-28 02:45:41.019 AO: Killing AudioOutputDSP
> 2008-02-28 02:45:41.019 Opening audio device 'plug:iec958'. ch 6(2) sr
> 48000
> 2008-02-28 02:45:41.020 Opening ALSA audio device 'plug:iec958'.
> 2008-02-28 02:45:41.032 in SetParameters(format=2, channels=6,
> rate=48000, buffer_time=100000, period_time=25000)
> 2008-02-28 02:45:41.034 get_buffer_size returned 4800
> 2008-02-28 02:45:41.034 set_period_time_near returned 20000
> 2008-02-28 02:45:41.034 get_period_size returned 960
> 2008-02-28 02:45:41.050 AO: Audio fragment size: 19200
> 2008-02-28 02:45:41.052 AO: create upmixer
> 2008-02-28 02:45:42.135 AO: create upmixer done with surround mode 2
> 2008-02-28 02:45:42.136 AO: Audio Stretch Factor: 1
> 2008-02-28 02:45:42.136 Audio Codec Used: not set
> 2008-02-28 02:45:42.136 AO: Ending reconfigure
> 2008-02-28 02:45:42.136 NVP: Enabling Audio
> 2008-02-28 02:45:42.136 AO: Killing AudioOutputDSP
> 2008-02-28 02:45:42.136 AO: kickoffOutputAudioLoop: pid = 16227
> 2008-02-28 02:45:42.136 AO: OutputAudioLoop: Stop Event
> 2008-02-28 02:45:42.136 AO: kickoffOutputAudioLoop exiting
>
>
>
> I can provide more extensive logs if necessary, but I feel as though
> I'm missing something glaringly obvious. :(

I *think* since you are seeing upmixer notes in your logs that you are
running a very recent SVN version?  If this is the case, I think you need to
set your upmix settings to passthrough or something like that (I haven't
updated but I saw some messages regarding this).  See if you can find that
setting.

Kevin
-------------- next part --------------
An HTML attachment was scrubbed...
URL: http://mythtv.org/pipermail/mythtv-users/attachments/20080228/d6a8ea27/attachment-0001.htm 