[MPlayer-dvb] On HD Channels no audio!

[Bill Pringlemeir]

On 24 Oct 2009, Raena Lea-Shannon <raen at internode.on.net> wrote:

> I have checked the list archives, google and gmane search on mplayer and
> I have updated by channels conf file with scan  and I have tried 
> inserting :pid[8192] into in the audio/video field in the channels.conf 
> file and I have checked mplayer -ac help and a53 and ac3 and passthrough 
> hwac3 are all ok and still no audio! just on the HD Channels.

I have the following in my '~/.mplayer/config'

# Use alsa drivers.
#ao=alsa
ao=alsa:device=plug=spdif
#channels=6 
ac=hwac3,hwdts,a52,

Are you using an spdif passthru?  This is what 'hwac3' is for.  If you
have this, you need to modify alsa.

 amixer -c 0 sset 'IEC958 Optical Raw' on

There is something wrong with the SVN version of mplayer and the
latest (or some versions) of alsa libs.  There is an "AES=6" parameter
that is sent to alsa when running in passthrough mode.  This is
incorrect.  There is some crazy langauge with alsa and there is a
'.asoundrc' file.  Mine is like this,

    ##<confdir:/usr/share/alsa/pcm/iec958.conf>
    pcm.!default {
        type plug
        slave.pcm "iec958:CARD=Live,DEV=0"
    }

The alsa configuration language is very complex (and powerful), but it
can be a bit of a barrier to entry.

Running this via SPDIF to a Sony AMP lets me received the AC3
channels.  There are various problems with the AC3 feeds from various
stations; if you see a station switching from 5/2 to 2 channels,
etc. There may be occasions that the sound via passthru will be
rejected by your AMP (or whatever you are using).  You can try the
following to ~/.mplayer/config,

[messed-up-channel]
#af-add=volume=3
af-add=surround
af-add=sub=50:5
af-add=center
af-add=lavcac3enc=1:448:2

and then run 'mplayer -profile messed-up-channel dvb://bad-channel'.
This method seems to produce better results, but the rear channels are
always mixed together.  With the passthrough, the rear channels are
completely seperate which is occasionally an interesting effect.

My reception is OTA and the last stuff about channel switching might
be paranoia and it is just BER effects.  However, I have seen others
report similar problems with different OS/programs.

Some one also reported an issue about the amount of buffering and
mplayer going crazy when the buffer is depleted with OTA signals.
This will also happen for any marginal channel.  The
linux-dvb-apps/util/szap/femon program can help to see if you have
problems.  BER values are ok, but if the signal lock goes then you
won't have luck viewing that channel with mplayer (or possibly
anything).

I am running Debian Lenny, so I think that should be close to what you
have.

hth,
Bill Pringlemeir.

SPDIF==IEC958 ~== AC3 passthru