[linux-dvb] Re: No audio, and interlacing problem with Nova-tcard and dvbstream

[jng_junk@greenmail.demon.co.uk]

On Fri, 7 Mar 2003, Holger Waechtler wrote:

> jng_junk@greenmail.demon.co.uk wrote:
> >>601 is the correct PID for BBC-1 on most transmitters. 602 is for second 
> >>language support - so films in original language might have sound on that 
> >>PID. Not quite sure where your scan results come from... dvbtune? 
> > 
> > 
> > My channels.conf came from the 'scan' utility that comes with the DVB
> > driver. I will have a look at what is going wrong later today. I suspect
> > it is a problem with 'scan'. I may try dvbtune as well, and compare the
> > results (I didn't know dvbtune was capable of producing the channels.conf
> > file). I don't think it'll be too difficult to fix once I've tracked down
> > the exact problem (hopefully the useful suggestion about dvbsnoop will
> > help here). If I come up with a fix, I'll post the suggestion here.
> 
> If it is a problem with multilinguality there is no real fix. The simple 
> szap/czap/tzap channel lists have no place for multiple audio PIDs. 
> You'll have to use a real DVB zapping application to explore this feature...

The multilinguality problem is the source of my troubles. However, I have
found a way of making 'scan' do the right thing for me. I emphasise "for
me". It turns out that the audio channel I want is always the first one
that is encountered when scanning. In scan.c there is this code:

                case 0x03:
                case 0x04:
                        s->audio_pid = elementary_pid;
                        break;

This effectively loses any previous audio PIDs already found for a given
channel. But since the structure is zeroed on creation, I can do this:

		if (s->audio_pid != 0) s->audio_pid = elementary_pid;

Of course, this isn't a very good way of solving the problem.

I've actually changed my copy of 'scan' to make a linked list of audio
channels, and output them all in channels.conf. So I get a line like this:

BBC ONE:641833330:INVERSION_OFF:BANDWIDTH_8_MHZ:FEC_3_4:FEC_NONE:QAM_16:TRANSMISSION_MODE_2K:GUARD_INTERVAL_1_32:HIERARCHY_NONE:600:601,602

Of course, anything that is already written to understand the previous 
format of channels.conf will not like this change.

I wonder if there is a way of automatically determining the correct 
channel?

I doubt it will be the case, but if anybody wants my linked-list changes 
to 'scan', I will happily provide them.

Many thanks to everybody who helped me on this. On to the next stage of my 
project...

James.




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