Why won't Myth play a particular local TV station?

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Why won't Myth play a particular local TV station?

Post by Bullwinkle » Thu May 22, 2014 6:30 pm

I am running Mythbuntu 12.04 at the backend. A HDHomeRun Dual is the input source. The frontend is running on Ubuntu 12.04. MythTV version is .25.

There is a new digital TV station that came on the air recently (former low power station that converted from analog to digital and upped their power) and for some reason neither the MythTV frontend nor XBMC when using the cMyth addon can play live or recorded programs from this station. All it displays is a black screen with occasional flashes of picture, plus some kind of green bar display in the lower right corner of the screen. Audio does play but is choppy. This happens on all four subchannels (all are standard definition) but ONLY on Linux, and ONLY when played using MythTV or XBMC.

The station plays just fine if ANY of the following are true:
  • I tune it with my TV's tuner.
  • I watch it using the MythTV frontend on my OS X box (running Mavericks). Apparently it's ONLY an issue when running under Linux.
  • I record it (using the MythTV backend) and play it using VLC on my frontend box (trying to play the recording in the MythTV frontend or XBMC does not work)
EVERY other station plays just fine (unless the signals strength drops out). It's only this new station that does this.

What information could I submit that might assist in explaining what the problem is, and how do I get that information?

I called the station and they claim they are not doing anything special with their signal.

Here are some parameters on the test recording I made (9 minues because it took me that long to figure out how to stop the recording once I had started it - I had really only wanted a short sample of a minute or so), from the OS X "VideoSpec" program - I have no idea if there is anything the slightest bit useful here. Only the Name line is edited:

*** General Parameters ***
- Name: (Program Title) - 2014-05-22, 2-03 AM - (subtitle).mpg
- Container: Mpeg Transport Stream
- Size: 305.14 MB
- Duration: 9mn 0s
- Bitrate: 4 512 Kbps

*** Video Track Parameters ***
- Format: MPEG-2 Video
- Bitrate: Max.: 4 200 Kbps / Average: 4 095 Kbps / Min.: ---
- Frame rate (fps): Max.: Undefined / Average: 29.970 / Min.: Undefined
- Encoding profile: Main@Main
- Image size: 704*480
- Pixel Aspect Ratio: Undefined
- Display Aspect Ratio: 4:3
- Interlacing: Interlaced - Top Field First

*** First Audio Track Parameters ***
- Format: AC3-A52
- Bitrate: 192 Kbps
- Resolution: 16 bits
- Rate: 48.0 KHz
- Channel(s): 2 (stereo)
- Position: Front: L R

*** Miscellaneous ***
- Subtitle(s): No Subtitle
- Album: Undefined
- Performer: Undefined
- Genre: Undefined
- Encoded date: Undefined
- Album artist: Undefined

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Re: Why won't Myth play a particular local TV station?

Post by stuartm » Mon May 26, 2014 10:26 am

If you could upload a sample somewhere that may help us to determine what the issue is. Which video playback profile are you using?

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Re: Why won't Myth play a particular local TV station?

Post by pvr4me » Mon May 26, 2014 3:24 pm

Also, what channel is giving you problems. Maybe someone else in the area can confirm whether or not it works for them.

The MacPorts guy.

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Re: Why won't Myth play a particular local TV station?

Post by Bullwinkle » Wed May 28, 2014 6:17 pm

Sorry, I was busy the last couple of days and did not get around to replying.

I am not sure where I could post a short sample file that would not be taken down for copyright reasons. Maybe I could try the subchannel that stays on their temperature monitor? The trick would be getting a short enough recording to upload. What is the easiest way to make a short recording (a few seconds) in MythTV?

The station is WMKG channels 49.1 through 49.4 in Muskegon County, Michigan. It is low power so it can probably only be received within about a 30 mile radius of the transmitter, give or take a few miles.

Since posting originally I also tried running the HDHomeRun software on my frontend system and streaming Live to VLC, and that works. It definitely seems to be some interaction between this station and the MythTV software, though I cannot imagine what since the problem only appears if using the Linux MythTV frontend or the cMyth addon in XBMC on a Linux box.

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