[mythtv-users] mythmusic iec958 help
Mark Greenwood
fatgerman at ntlworld.com
Sun Jul 6 13:22:56 UTC 2008
On Sunday 06 July 2008 14:13:28 Richard Shaw wrote:
> On Sun, Jul 6, 2008 at 12:35 AM, Alen Edwards
> <allen.edwards at oldpaloalto.com> wrote:
> > Rich West wrote:
> >> Joe Henley wrote:
> >>> Gregg,
> >>>
> >>> From the posts above it doesn't look like it's going too well. I
> >>> continue to believe you will need to replace your sound card if you want
> >>> to get 44.1KHz signals into your receiver.
> >>>
> >>> Have you checked the SoundBlaster site (or googled) for clarification on
> >>> what your specific card will do? Allen's comments above about
> >>> "sometimes spdif means upto 48KHz" is not 100%. Sometimes it's 48KHz
> >>> only; trust me, been there, done that. ... and paid the return shipping
> >>> for a limited capability card.
> >>>
> >>> If your Soundblaster is not designed to output 44.1KHz via spdif, no
> >>> tweaking of alsa parameters, etc. will help.
> >>>
> >>> If your particular SB model will support 44.1KHz, then remove .asoundrc
> >>> from /root , /home, and /etc, and anywhere else it resides. IIRC, you
> >>> have already removed PukeAudio, so from there you can start using
> >>> alsamixer to unmute the iec958 items.
> >>>
> >>> The most common (from what I read on sites like this) successful MythTV
> >>> settings are:
> >>> Audio output device = ALSA: spdif
> >>> Passthru output device = Default
> >>> Max audio channels = stereo (The 5.1 setting is currently broken. Use
> >>> "stereo" and you'll still get 5.1 sound out of the system.)
> >>> Upmix = passive
> >>> Enable AC3 to SPDIF passthru = check
> >>> Enable DTS to SPDIF passthru = check
> >>> Enable internal volume controls = check
> >>> Mixer device = default
> >>> Mixer controls = Master
> >>>
> >>> What will work for you is probably very similar to this. If this
> >>> doesn't work first time, then check the wiki for ways to determine good
> >>> alternatives to "Audio output device = ALSA: spdif". This setting seems
> >>> to have several different incantations; and seems to be the one most
> >>> people have to change.
> >>>
> >>> Good luch, you _will_ eventually succeed,
> >> For more information, check out:
> >> http://www.mythtv.org/wiki/index.php/Configuring_Digital_Sound_with_AC3_and_SPDIF
> >>
> >> That page will walk you through what steps to take to:
> >> o get spdif sound working with linux (Fedora) - something you already
> >> have working
> >> o get the configuration set up to work with Myth (and MythVideo) for 5.1
> >> and stereo output - something you already have working
> >> o and get the configuration set up to work with MythMusic - the piece
> >> you are trying to get working
> >>
> >> More than likely, you're using a system with on-board SPDIF 5.1
> >> surround.. if that is the case, then it should be able to be done (and
> >> if it is AC97 chipset based, it is definitely possible).
> >>
> >> The key piece to get MythMusic working when you have all of the other
> >> components working is by setting "Max audio channels = stereo".
> >>
> >> -Rich
> >
> > That wiki is good.
> > Just don't get distracted with this one:
> > http://www.mythtv.org/wiki/index.php/Configuring_Digital_Sound
> > It doesn't work.
> >
> > Allen
>
> I hope I'm not hijacking this thread too much but I have been
> following all of these sound/spdif/iec958 threads and I've gotten
> myself more educated on this with the side effect of getting more
> confused as well... I've read every wiki I could find (both Mythtv
> ones and the alsa one) I think a lot of the info may be slightly old.
> For instance, no matter what I do the output of aplay -L is:
>
> [root at calvin ~]# aplay -L
> front:CARD=CK8S,DEV=0
> NVidia CK8S, NVidia CK8S
> Front speakers
> surround40:CARD=CK8S,DEV=0
> NVidia CK8S, NVidia CK8S
> 4.0 Surround output to Front and Rear speakers
> surround41:CARD=CK8S,DEV=0
> NVidia CK8S, NVidia CK8S
> 4.1 Surround output to Front, Rear and Subwoofer speakers
> surround50:CARD=CK8S,DEV=0
> NVidia CK8S, NVidia CK8S
> 5.0 Surround output to Front, Center and Rear speakers
> surround51:CARD=CK8S,DEV=0
> NVidia CK8S, NVidia CK8S
> 5.1 Surround output to Front, Center, Rear and Subwoofer speakers
> null
> Discard all samples (playback) or generate zero samples (capture)
> ---
>
> The only thing I have found that effects the above output is to edit
> /etc/alsa/alsa.conf and turn on the two options that are off
> (something about simple names and extended info).
>
> I have no idea what got things working for me again but I did the
> "alsactl names" to generate a /etc/asound.names file. I'm not sure if
> this actually does anything and I noticed that this option is
> depreciated in the help.
>
> I think I *MIGHT* have 44.1kHz working in mythmusic with a nForce
> chipset but the conversion to 48kHz may be happening somewhere else...
>
> mythfrontend settings:
> Default audio device: ALSA:plug:spdif:0 (from asound.names)
> Passthough device: ALSA:iec958{AES0=0x02}
> both AC3/DTS checked,
> 2 channels.
>
> section of mythfrontend log:
> ---
> 2008-07-05 21:37:44.739 Opening audio device 'plug:spdif:0'. ch 2(2) sr 44100
> 2008-07-05 21:37:44.740 Opening ALSA audio device 'plug:spdif:0'.
> MMX detected. Using fast method !
> ---
>
> Another thing that bothers me is that myth uses IEC958 w/ AES0=0x02
> but Xine uses AES0=0x06 (verified with iecset -x when both are playing
> back a DVD), both of which are "non-audio" and a sample rate of 48kHz
> which I assume means that the stream is not meant to be processed but
> just passed along...
>
> I'm sure I'm forgetting something as I stayed up too late last night
> trying things and the only thing holding me up is my morning coffee...
>
> I would still like to get both analog and digital output
> simultaneously at some point but I think I'm going to give up for now
> so my wife doesn't kill me.
I'm not sure if I'm understanding the problem correctly, but I'm using a Creative USB sound card which has both analogue and optical outputs. The optical output is connected to my surround processor. All I did was to leave myth set to use ALSA:default as its output and enable pass-through for AC3 and DTS, and I get 5.1 surround out of the optical output (assuming I'm playing a DVD. If I'm watching TV I get stereo). I haven't checked to see if any resampling is ocurring, but it doesn't matter - it just works. If I set myth to use the iec958 option, I get nothing at all. Have you tried just using ALSA:default? Or have you tried using an alternative sound card? USB cards with optical I/O are very cheap these days.
Mark
>
> Richard
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