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



jng_junk@greenmail.demon.co.uk wrote:
Hi there. I'd be extremely grateful if there is anybody out there who could help me with a few simple DVB related problems. I have recently bought a Hauppauge Nova-t card and I am trying to get it working with Linux (it works fine on Windows, but that's no use!).

By the way, I already sent this message to the dvbtools mailing list, but I was told this would be a more appropriate forum.

I checked out the latest DVB drivers, and latest dvbstream. I built them without any problems. The problem comes when I try to watch live TV. I'm using mplayer to play the MPEG stream. But I've encountered a few problems:

1) My channels.conf file seems to have the wrong ID for the audio channel. I ran 'scan' and it found a sensible looking channel selection. Here is an example line:

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

I don't know if this is the right thing to do but I used the IDs from the
line above (ie. 600 and 602) to try and play a live broadcast, ie.:

./dvbstream -o 8192 | ./ts2pes 600 602 | mplayer -

The video works fine but I have no audio. I found by experimentation that if I used ID 601 instead of 602, the audio worked? Is 'scan' producing an incorrect channels.conf, or have I misunderstood something?
Hmm, could you please run a stream analyzer (e.g. dvbsnoop) on the PMT PID and look what audio PID is actually announced? Some (multilingual) channels have more than one Audio-PID, in this case scan will print the last one in the channel list.

There are even some broadcasters which don't transmit correct Audio PIDs for their multilingual services.


2) Finally, when I do get working video, all is fine until there is rapid
motion in the animation. Under these conditions I get some pretty horrible
looking interlacing problems. The effect can be seen if somebody waves
their hands. Lots of horizontal stripes appear around the fast moving
hands. It's as though alternate lines are plotted at the wrong horizontal
offset. It's definitely some kind of interlacing problem - I have seen it
before on DVD playback when I have got the wrong interlace settings.

I tried playing around with some of the mplayer interlacing options but only seemed to make things worse!
Sounds like an mplayer decoder bug. Can you please report this behaviour to the mplayer mailing list? Have you tried other MPEG software decoders for comparision?


So, if anybody can help me I'd be very grateful. If I can get things
working I hope to develop some useful DVB software, so I can hopefully
repay any help back to the community.
Maybe you can add software decoder support to VDR or Enigma? Based on ffmpeg and DirectFB this should be not too hard...

Holger



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