[vdr] Understanding AC-3

Rob Davis rob at davis-family.info
Thu Sep 2 19:05:23 CEST 2010

On 02/09/10 11:05, L. Hanisch wrote:
> Hi,
> Just an additional info for the ones who want to help - the
> pvrinput-plugin passes through the TS from the HD PVR to vdr, there's
> nothing changed.
> So hopefully the plugin is not the one to blame for... :-)
> I posted a sample PAT and PMT of the HD PVR in february, perhaps it can
> be used to clarify something.

> http://www.linuxtv.org/pipermail/vdr/2010-February/022400.html

How do you create the PAT and PMT files and then understand them.
I'm pretty sure that sample file was only mp3 input instead of AC3 
digital which is what I use now..

> Lars.
> Am 02.09.2010 15:21, schrieb Rob Davis:
>> Hi Guy's,
>> How do you go about understanding AC-3 within a VDR context?
>> (apart from reading up on it online - which now has my head spinning).
>> I have a Hauppauge PVR-HD and two ATSC cards. The ATSC cards work as
>> they should and with the new atsc/dn patch on
>> 1.7.15 now have the correct dpids.
>> However, if I turn on add new transponders or update pids, then my
>> Hauppauge PVR channels lose their dpid values..
>> Sep 1 19:10:33 oac vdr: [8186] changing pids of channel 920 from
>> 4113+4097=27:0;4352=eng at 106:0:0 to 4113+4097=27:0:0:0
>> If I keep automatic channel updates off, then xineliboutput and
>> streamdev work for these channels, but vdr-vnsi (xbmc)
>> and vdr-xine don't (no audio)..
>> I'm assuming vdr parses the ac3 headers in some way and sends
>> information onto the playback frontend. How would I go
>> about seeing what those headers might be and looking into patching
>> pat.c accordingly?
>> I noticed all the comments about e-ac3 and wonder if a similar patch
>> should be made for this device.
>> As an aside, vdr recordings from these channels play back fine in
>> vdr-xine.
>> So, more specifically, I suppose I would like to know how to find out
>> I'm pretty sure it falls under this:
>> case 6: // STREAMTYPE_13818_PES_PRIVATE
>> But I'd be interested in seeing the flow through this section of pat.c
>> and what is happening.. Mainly to see if
>> something needs to be forced on?
>> I can create a five second VDR recording if someone wants to see what
>> the TS stream looks like.. But I'd be interested
>> in diagnosing it myself..
>> Thanks.
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Rob Davis

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