Can't see ATSC subchannel video, audio OK

[Braklet]

v1.3.11

I'm in the US, and just reconfigured my ATSC tuner after our broadcast DTV transition. One channel in particular gives me problems; I can hear the audio but video remains blank (or remains stuck on the previous video buffer contents).

Both of my digital TVs properly tune this channel with their embedded ATSC tuners, so this appears to be an issue between my tuner card (AverMedia A180) and the GB-PVR scanner. Note that the scanner preview window exhibits the same behavior (audio OK, no video). I wonder if there's a problem with the tuner line that the scanner comes up with?

I extracted the relevant portions of config.exe.log (see below). The problematic channel is 50.2 RTN. Just guessing, the video_PID doesn't seem to be anywhere near the video_PIDs for 50.1 or 50.3 (which both tune correctly). Does anybody know of a way to debug the scanner? Any other suggestions for me to manually compose correct tuning parameters? Thanks for any help!

Code:

2009-06-15 18:41:03.102    INFO    [1]    Tranponder information for: 49,0,0
<transponder>
<network_id>0</network_id>
<transport_stream_id>1855</transport_stream_id>
<original_network_id>0</original_network_id>
<service>
  <service_name>WRAZ-HD</service_name>
  <TSID>1855</TSID>
  <service_ID>3</service_ID>
  <service_type>0</service_type>
  <pmt_PID>48</pmt_PID>
  <pcr_PID>49</pcr_PID>
  <video_PID>49</video_PID>
  <major_channel_number>50</major_channel_number>
  <minor_channel_number>1</minor_channel_number>
  <audio_PID lang="000" audio_type="0" AC3="true">52</audio_PID>
</service>
<service>
  <service_name>RTN</service_name>
  <TSID>1855</TSID>
  <service_ID>4</service_ID>
  <service_type>0</service_type>
  <pmt_PID>64</pmt_PID>
  <pcr_PID>65</pcr_PID>
  <video_PID>2852</video_PID>
  <major_channel_number>50</major_channel_number>
  <minor_channel_number>2</minor_channel_number>
  <audio_PID lang="eng" audio_type="0" active="true">68</audio_PID>
</service>
<service>
  <service_name>WRAZ 2</service_name>
  <TSID>1855</TSID>
  <service_ID>5</service_ID>
  <service_type>0</service_type>
  <pmt_PID>80</pmt_PID>
  <pcr_PID>81</pcr_PID>
  <video_PID>81</video_PID>
  <major_channel_number>50</major_channel_number>
  <minor_channel_number>3</minor_channel_number>
  <audio_PID lang="000" audio_type="0" AC3="true">84</audio_PID>
</service>
</transponder>
2009-06-15 18:41:03.102    VERBOSE    [1]    Adding tuning request: 49,0,0~P:3~V:49~A:52~PMT:48~PCR:49~N:>50.1  WRAZ-HD (000(AC3))
2009-06-15 18:41:03.102    VERBOSE    [1]    Adding tuning request: 49,0,0~P:4~V:2852~A:68~PMT:64~PCR:65~N:>50.2  RTN (eng)
2009-06-15 18:41:03.102    VERBOSE    [1]    Adding tuning request: 49,0,0~P:5~V:81~A:84~PMT:80~PCR:81~N:>50.3  WRAZ 2 (000(AC3))

[Braklet]

Re-reading my log excerpt, I just noticed that for the working channels, video_PID == pcr_PID. The broken channel has video_PID != pcr_PID. Maybe it would magically work if I set the broken channel's video_PID to pcr_PID?

How would I manually modify the tuning parameters? The scanner has worked flawlessly for me before now, so I haven't really dug into tuning parameter storage. Edit config.xml?

[sub]

If you're able to temporarily set you multiplexer to 'FullTS', then record a minute or two of 'WRAZ-HD', then use cutchunk (attached) to cut a 30MB chunk from the file, and make it available to me somehow, then I'll check it out for you. After this set your multiplexer back to whatever it was on previously.

The app doesnt actually use the PCR pid, so unlikely to be related to that.

[Braklet]

I'll dig around through the config app and see what I can do about getting a full transport stream for you, sub. From memory, I'm using the stuff that came with XP, and my recordings end up in DVR-MS containers. (This was the only format that worked for me, and predates GB-PVR TS support IIRC.)

What tools can you use to digest TS and "see" what's inside?

Thanks, sub.

[johnsonx42]

You can edit the tuning request by hand in the tuner config screen (not in the mapping screen). I find it's easiest if you copy the tuning request to notepad, edit it there, then copy it back.

AFTER doing what sub asked (because if config is reading the wrong id out of the stream, it may affect others... we all have to do our part), then you should change the V: parameter in that tuning request to 65 and see what happens.

[sub]

What tools can you use to digest TS and "see" what's inside?

I'd probably end up looking at it with TSReader.

Its probably being confused by some data stream, and thinking its the video stream.

[whurlston]

I agree with Johnsonx42. The video PID and audio PID are almost always near each other. I'm willing to bet that your video PID should be 65.

[Braklet]

OK sub, I recorded a bit of WRAZ-HD using Full TS, carved off a 30M chunk, and made it available. (Please see PM for URI, let me know when you have it.) I briefly tried playing with TSReader Lite but couldn't figure out how to feed it a HDD file, so gave up.

All: I manually changed video_PID in the tuning request to 65 (same as pcr_PID) and the channel displayed normally.

Thanks for everybody's suggestions.

[johnsonx42]

Glad you got it sorted. sub will no doubt figure out why it got the wrong video pid in the first place.

I should have mentioned (and will do so now for anyone else who finds this thread) that you could also 'fix' the tuning request by modifying the scan-1.cache file in the BDA folder.

[Braklet]

you could also 'fix' the tuning request by modifying the scan-1.cache file in the BDA folder.

Ah! That's good to know. I was searching around through config.xml and gbpvr.db3 for any scan or tuning information, but came up empty.

While I was playing with it, I also wondered how to clear out results from previous scans. Sounds like you came up with the solution!

Thanks for the info.