[mythtv-users] Recording digital-audio channels over FireWire appears to not work in MythTV

[Steve Adeff]

On Thursday 12 January 2006 13:22, Scott Alfter wrote:
> The local cable system has a bunch of audio channels up in the 900s with
> music, talk radio, etc.  Out of curiosity, I tried recording from them over
> FireWire with the same tools that grab HD channels and such.  With the
> cable box set to one of the audio channels, it spits out a transport stream
> containing just an AC3 audio stream--no video.  test-mpeg2 captures this
> stream with no problems. mplayer should be able to play it; I know it can
> demux it and dump the AC3 stream to a file (use the -dumpaudio option, with
> -dumpfile to specify an output filename).  The AC3 file can then be played
> as-is or converted to another format.
>
> The talk-radio stream I grabbed as a test looks like it's encoded at 128
> kbps. The graphics displayed on the cable box's analog outputs are
> generated by the cable box.  They're not part of the incoming stream, which
> is why the captured stream contains only audio.
>
> Where MythTV comes into this is that it you would think that since it's
> capable of recording from FireWire-equipped cable boxes, it'd be able to
> grab these audio-only streams.  It would appear that the lack of a video
> stream confuses mythbackend, though, as you end up with a zero-byte file.
>
> I know that radio != TV, but it seems to me that this could be a nice extra
> capability that probably wouldn't need much extra work to get it working
> right. I suspect there are some sanity checks of the incoming stream that
> are getting confused by the lack of video; disabling these checks for
> certain channels (and disabling other processing, such as commercial
> flagging, that won't work without video) would get the job done.
>

there is a patch in SVN for doing similar for DVB radio, it should work for 
this as well since it creates its own video. I haven't tried it personally 
yet though...

-- 
Steve