[mythtv] Re: TS Timing issues

Jesper Sörensen jesper at datapartner.se
Sat Mar 19 19:09:13 UTC 2005


William Uther wrote:

> I'm sorry if I'm stating the obvious or something, but I feel it would 
> be nice with a better structure for helping new people help around 
> here.  Helping new people help => more devs => quicker fixes and a 
> more vibrant community.  If people have to fight to join the 
> mythtv-dev community, they wont.
>
> And so I'll ask again.  Where is the best documentation on dvb and 
> mpeg2 decoding?  How do I find out what a PCR PID is, and how I might 
> see if it is separate from a video PID?  I've tried google searching.  
> I've looked through the the linuxtv wiki.  I'm slowly finding stuff, 
> but I have the distinct feeling that a few pointers from those who've 
> been here before would really speed things up.  It would certainly 
> help more than someone telling me what a bug tracking system is.


Ok, so you're looking for good & simple docs or some kind of newbie's 
guide? Let me know if you find it. As far as I know there is no easy way 
in to this. It takes time, hard work and lots of reading. Sure, it sucks 
but that's how it is. Do you really think we all just sit here trying to 
keep all of the magic docs secret, to keep any new developers from 
entering the "exclusive" club? It would be great with a big "developer's 
guide to Myth" but AFAIK nobody has written it yet.

I see you posted some messages to the list but obviously you didn't get 
the replies you wanted. I can only speak for myself but with the amount 
of traffic on the Myth lists (and all other lists I'm on too) it's 
impossible to read everything and much less reply and "help" everyone 
with an issue, even though we all would want to. Most of the time I'm 
just scanning the subjects for interesting stuff and doing "mark folder 
as read" on the rest, so if your posts were ignored it's probably 
because you didn't trigger my interest or went below my cost/benefit 
ratio. I've had my share of "no replies" too - that's life.

Quick specific questions with a good subject tend to attract more 
interest than "four issues" and pages of logs and info. That might work 
with some people and on a good day I might even have replied, but if you 
happen to post on a busy mail day or when I'm extra tired it probably 
gets filtered out.

Things do slip through the cracks, so give it some time and try again 
with a better subject and more concise info and maybe you're lucky, and 
use bugzilla for bugs like I said before. And the same rules apply 
there, keep it as concise as possible (I know - it's damn hard, 
especially when you don't know what's important and what's not), and it 
doesn't hurt to shoot off an email to the dev list (with a good subject 
:-) to draw some attention to the bugzilla bug if it's new or has some 
new info.

I haven't seen any "[DVB] What is PCRPID?" or "Where do I find DVB 
docs?" subjects from you on this list but here is a little something to 
keep you occupied. :-)

Please try the attached patch for PCRPID logging. I haven't tried it but 
it's a one liner so I think you can sort it out if there's something wrong.

As you can see on the LinuxTV wiki, the DVB docs you need are the 
ISO/ITU-T/ETSI standards:
http://www.linuxtv.org/wiki/index.php/MPEG2_Standard
http://www.linuxtv.org/wiki/index.php/DVB_Standard

The basic DVB stuff is in H.222.0 (transport stream format, PAT, PMT 
etc), and the higher level DVB stuff (NIT, SDT, EIT...) is in ETSI EN 
300 468. There are links in the wiki to where you can download those 
docs for free.

-------------- next part --------------
Index: libs/libmythtv/dvbrecorder.cpp
===================================================================
RCS file: /var/lib/mythcvs/mythtv/libs/libmythtv/dvbrecorder.cpp,v
retrieving revision 1.46
diff -u -r1.46 dvbrecorder.cpp
--- libs/libmythtv/dvbrecorder.cpp	19 Mar 2005 06:51:41 -0000	1.46
+++ libs/libmythtv/dvbrecorder.cpp	19 Mar 2005 13:55:39 -0000
@@ -492,6 +492,8 @@
         }
     }
 
+    RECORD(QString("PCRPID = %1").arg(m_pmt.PCRPID));
+
     RECORD(QString("AutoPID Complete - PAT/PMT Loaded for service"));
 
     if (m_pmt.FTA())


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