[mythtv-users] HDTV and Myth Chan Scan

Michael Haan michael.haan at gmail.com
Fri Feb 17 21:02:55 UTC 2006

On 2/17/06, R. G. Newbury <newbury at mandamus.org> wrote:
> Michael Haan wrote:
> > On 2/17/06, *R. G. Newbury* <newbury at mandamus.org
> > <mailto:newbury at mandamus.org>> wrote:
> >
> >       Take a look at the channel table. There must be an mplexid entry
> >     for
> >     channel 213 (as well as a serviceid). You will need to do:
> >
> >     update channnel set mplexid = 'x', serviceid='y' where
> channum='213';
> >
> >     Geoff
> >
> >
> > Yeah, I'm just curious why the scan didn't do that.  From the table
> > above, how do I know which mplexid to set?  And where do I find the
> > service ids?
> Because the scan doesn't. Although it will now import a channel.conf
> file and it may massage that file sufficiently to do that.
> I'm not going to repeat things at great length yet again. Go to gossamer
> threads and search on a subject title "pcHDTV Sweet..."
> This thread is specifically for  North American HTDV on cable using
> QAM_256.  It may help with other setups however.
> You will need some programs referred to in that thread:  atscscan and
> azap. and mplayer for testing.
> atscscan will tune all the standard frequencies and read the stream for
> video id, audio id and program id information. It may or may not be able
> to parse the channel name and it will not generally find out the cable
> channel number.
> You will get a list of usable outputs, which will make up your
> channels.conf. These are "channels".. and many are in fact music (audio
> only) feeds. With my cableco I get numbers up to about 800 . Most of the
> audio streams are usable btw.
> You can tune each channel with azap in one console and capture the
> stream with 'cat /dev/dvb/adapter0/dvr0 > test.mpg' in another console
> then play it back with 'mplayer test.mpg'.
> Someone posted a script which will do the things on the above line
> automagically and find the unencrypted streams.
> You can also tune with azap in one console and use mplayer -vid x -aid y
> /dev/dvb/adapter0/dvr0 where x and y are the video and audio ids found
> with the scan.
> Each frequency carries multiple streams. Each frequency is uniquely
> differentiated by its mplexid in the dtv_multiplex table (together with
> the modulation and other simliar details which all of the streams have
> for that frequency.
> The channel table then needs entries for the mplexid, to know the
> freqeuency and the serviceid to know which stream to capture for channel
> 213. Along the way, the system also knows that this channel is in the
> sourceid=x group and therefor that it can use the tuners which are
> matched to that sourceid.
> The particular problem is that, at least around here, cableco's do not
> have to send channel name information in the stream. They (also)
> determine the 'channel number' which is just a convenient and unique
> marker for the channel. It does not have any relevance to the tuning
> problem. And, the cableco can and does change the program id (or
> serviceid) for channel streams..
> All of which make it damn difficult to scan for and extract the proper
> data.
> Geoff
> --
>        R. Geoffrey Newbury
>      Barrister and Solicitor
> Suite 106, 150 Lakeshore Road West
>     Mississauga, Ontario, L5H 3R2
>   905-271-9600  Fax 905-271-1638
>        newbury at mandamus.org
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Right, to be clear, I'm not asking for assistance doing this the manual way
- I've done that successfully several times before.  I was just trying
figure out if the scan was broken or not.  From your post, it seems that it
is not - so, good.  Thanks for all the responses.
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