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PostPosted: Fri Feb 27, 2004 10:10 am 
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Joined: Tue Feb 03, 2004 3:23 am
Posts: 159
Location: Friesland, The Netherlands
I am not able to pass the AC3 audio through to my AV receiver. At the moment I have AC3 pass through enabled in the general setup and watching TV, listening to music and watching video works just fine through the digital 3.5mm jack digital output of my Soundblaster Audigy card (using snd-emu10k1 module, KnoppMyth R4V2).

When I play DivX films with AC3 sound using the default mplayer options it's played back using software AC3 decoding to pro logic. I'd like this AC3 sound to be fed to my AV receiver and let the receiver do the decoding.

I've searched both this forum, the gossamer forum and googled but no working answer as of yet. Everybody suggests adding the -ac hwac3, options to the mplayer command line. However when I try this I hear a loud ratling noise when playing AC3 audio. Non AC3 DivX films play back just fine with these settings. The mplayer manpage don't give any clues.

So it appears the -ac hwac3, options change the behaviour of mplayer with AC3 audio, but it's not really what I'd like.

Anyone tried a similar setup and got it working? Are there perhaps known issues with the digital out of the Audigy? The ALSA project page suggests it should work.

Thanks for your time.


Willem


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 Post subject: spdif out
PostPosted: Sat Feb 28, 2004 5:52 am 
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Joined: Sun Jan 04, 2004 3:25 pm
Posts: 49
Location: Coventry England
the -ac option is a decoder option, the -ao options are for selecting the output type.

-ao=alsa9:spdif

should work, although I've not tried it on and Audigy. Also adding
-channels=6 might be needed for suround sound.

bye
Pete


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 Post subject:
PostPosted: Sun Feb 29, 2004 9:31 am 
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Joined: Tue Feb 03, 2004 3:23 am
Posts: 159
Location: Friesland, The Netherlands
Thanks Pete for your reply. Unfortunately it still doesn't work. It looks like alsa9:spdif is not recognised as an available mixer device.

Here's some output from ~mythtv/.xsession-errors when playing a DivX film with AC3 sound using mplayer and the -ao alsa9:spdif option:

Playing /myth/video/TheRecruitCD2.avi
AVI file format detected.
VIDEO: [XVID] 640x352 24bpp 23.98 fps 1120.8 kbps (136.8 kbyte/s)
Clip info:
Software: Nandub v1.0rc2
==========================================================================
Opening audio decoder: [liba52] AC3 decoding with liba52
Using SSE optimized IMDCT transform
AC3: 5.1 (3f+2r+lfe) 48000 Hz 448.0 kbit/s
Using MMX optimized resampler
AUDIO: 48000 Hz, 2 ch, 16 bit (0x10), ratio: 56000->192000 (448.0 kbit)
Selected audio codec: [a52] afm:liba52 (AC3-liba52)
==========================================================================
vo: X11 running at 800x600 with depth 24 and 32 bpp (":0.0" => local display)
==========================================================================
Opening video decoder: [ffmpeg] FFmpeg's libavcodec codec family
Selected video codec: [ffodivx] vfm:ffmpeg (FFmpeg MPEG-4)
==========================================================================
Checking audio filter chain for 48000Hz/2ch/16bit -> 48000Hz/2ch/16bit...
AF_pre: af format: 2 bps, 2 ch, 48000 hz, little endian signed int
AF_pre: 48000Hz 2ch Signed 16-bit (Little-Endian)
ALSA lib setup.c:548:(add_elem) Cannot obtain info for CTL elem (MIXER,'IEC958 Optical Raw Playback Switch',0,0,0): No such file or directory
Could not open/initialize audio device -> no sound.
alsa-init: testing and bugreports are welcome.
alsa-init: requested format: 48000 Hz, 2 channels, Signed 16-bit (Little-Endian)
alsa-init: soundcard set to spdif
alsa-init: playback open error: No such file or directory
Audio: no sound
Starting playback...
VDec: vo config request - 640 x 352 (preferred csp: Planar YV12)
VDec: using Planar YV12 as output csp (no 0)
Movie-Aspect is 1.82:1 - prescaling to correct movie aspect.
VO: [xv] 640x352 => 640x352 Planar YV12 [fs] [zoom]



I don't know which file or directory it's missing. Some /dev/* file? Up until now the best I get is starting mplayer without the -ao and -ac options. Then the audio is routed through the digital out of the Audigy card to the receiver. Mplayer uses the software AC3 decoding then:

Selected audio codec: [a52] afm:liba52 (AC3-liba52)

is what I see in ~mythtv/.xsession-errors.

Here's the messages in ~mythtv/.xsession-errors when I try the -ac hwac3, option:

Playing /myth/video/TheRecruitCD2.avi
AVI file format detected.
VIDEO: [XVID] 640x352 24bpp 23.98 fps 1120.8 kbps (136.8 kbyte/s)
Clip info:
Software: Nandub v1.0rc2
==========================================================================
Forced audio codec: hwac3
Opening audio decoder: [hwac3] AC3 pass-through SP/DIF
No accelerated IMDCT transform found
AUDIO: 48000 Hz, 2 ch, 16 bit (0x400), ratio: 56000->192000 (448.0 kbit)
Selected audio codec: [hwac3] afm:hwac3 (AC3 through SPDIF)
==========================================================================
vo: X11 running at 800x600 with depth 24 and 32 bpp (":0.0" => local display)
==========================================================================
Opening video decoder: [ffmpeg] FFmpeg's libavcodec codec family
Selected video codec: [ffodivx] vfm:ffmpeg (FFmpeg MPEG-4)
==========================================================================
Checking audio filter chain for 48000Hz/2ch/16bit -> 48000Hz/2ch/8bit...
AF_pre: af format: 2 bps, 2 ch, 48000 hz, big endian AC3
AF_pre: 48000Hz 2ch AC3
Can't set audio device /dev/dsp to AC3 output, trying S16...
AO: [oss] 48000Hz 2ch Signed 16-bit (Little-Endian) (2 bps)
Building audio filter chain for 48000Hz/2ch/16bit -> 48000Hz/2ch/16bit...
[format] Sample format big endian AC3 not yet supported
[libaf] Reinitialization did not work, audio filter 'format' returned error code -2
Couldn't find matching filter / ao format!
Starting playback...
VDec: vo config request - 640 x 352 (preferred csp: Planar YV12)
VDec: using Planar YV12 as output csp (no 0)
Movie-Aspect is 1.82:1 - prescaling to correct movie aspect.
VO: [xv] 640x352 => 640x352 Planar YV12 [fs] [zoom]





Using these settings I hear a loud chirping noise. Non AC3 files play back fine.

Does anyone have an idea looking at the output mplayer creates?


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 Post subject:
PostPosted: Tue Mar 02, 2004 2:49 am 
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Joined: Tue Feb 03, 2004 3:23 am
Posts: 159
Location: Friesland, The Netherlands
Problem solved. I got my hands on a Soundblaster Live! 1024. Replaced my Audigy with this one and it worked straight away. Can't be bothered trying to find out why the Audigy didn't work (it's Creative's first Audigy model, maybe later hardware has better support).

Interesting observation: using -ao alsa9:spdif -ac hwac3, allowed me to use AC3 pass through but some MPEG1 clips played back way too fast (Simpsons sounded like Chipmunks). Using -ao alsa9:hw:0,3 -ac hwac3, works perfectly. Non AC3 is decoded properly and AC3 is passed through to my AV receiver.


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 Post subject:
PostPosted: Thu Mar 25, 2004 4:02 pm 
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Joined: Mon Mar 15, 2004 11:17 pm
Posts: 53
so you just have "-ao alsa9:0,3 -ac hwac3" at the end of the mplayer line?
humm i have the same now and ac3 sound will play but non ac3 sound doesnt play at all, any idea how i could fix it seeing as you got it working?
i tryed with spdif insted of 0,3 and 0,0 tru 0,5 no luck ac3 stuff will play non ac3 stuff no sound

any help would be greatly appriciated

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Kaziya

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Asus Motherboard A7V8X-X
AMD Athlon XP 2500+ (333FSB)
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 Post subject:
PostPosted: Thu Mar 25, 2004 10:24 pm 
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Joined: Mon Oct 06, 2003 10:38 am
Posts: 4978
Location: Nashville, TN
well I've never tried any of this, but I did note that you have

-ao alsa9:0,3 -ac hwac3
and he has
-ao alsa9:hw:0,3 -ac hwac3

so unless it's a typo you may try that.


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 Post subject:
PostPosted: Thu Mar 25, 2004 11:30 pm 
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Joined: Mon Mar 15, 2004 11:17 pm
Posts: 53
umm that wasnt a typo i admit i missed that bit, tho i just tryed it and it made no diffrence, i think the problem is with the -ac hwac3 is to use the hardware ac3 codec and with anything that isnt ac3 encoded it wount play(cause the hardware can only decode ac3)
its my guess, so im wondering why it works for both ac3 and non ac3 for him but atm its either ac3 5.1 or not
ok this was what seemed to work for me i set the vob extension so it has its own command app to load and set the line there so non ac3 plays without that at the end and anything .vob plays with it
which is just as well seeing as if its vob it will likly have ac3 and if it isnt ill just rename it

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Kaziya

HTPC:

Asus Motherboard A7V8X-X
AMD Athlon XP 2500+ (333FSB)
256MB DDR PC2700
Nvidia Geforce 3 Ti 200
WinTV-PVR-250MCE
Logitech wireliss MXDuo (keyboard and mouse)
Ati Remote Wonder


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 Post subject:
PostPosted: Fri Mar 26, 2004 2:21 am 
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Joined: Tue Feb 03, 2004 3:23 am
Posts: 159
Location: Friesland, The Netherlands
Try -ao alsa:hw:0,3 -ac hwac3,

The trailing comma after hwac3 does the trick here. It tells mplayer to do AC3 passtrough for content with AC3 audio and try software decoding or other codecs for anything else. More info about this in the mplayer manpages.


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 Post subject:
PostPosted: Fri Mar 26, 2004 9:36 am 
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Joined: Mon Mar 15, 2004 11:17 pm
Posts: 53
oh ok, didnt relize that, ill try that thanks

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Kaziya

HTPC:

Asus Motherboard A7V8X-X
AMD Athlon XP 2500+ (333FSB)
256MB DDR PC2700
Nvidia Geforce 3 Ti 200
WinTV-PVR-250MCE
Logitech wireliss MXDuo (keyboard and mouse)
Ati Remote Wonder


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 Post subject:
PostPosted: Fri Mar 26, 2004 9:46 am 
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Joined: Mon Mar 15, 2004 11:17 pm
Posts: 53
yep yep that made the diffrence
thanks!!

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Kaziya

HTPC:

Asus Motherboard A7V8X-X
AMD Athlon XP 2500+ (333FSB)
256MB DDR PC2700
Nvidia Geforce 3 Ti 200
WinTV-PVR-250MCE
Logitech wireliss MXDuo (keyboard and mouse)
Ati Remote Wonder


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