Long term broadcast fault on Bravo?

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bfginger

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#318131 19-Dec-2024 07:59

I've been seeing black bars on the left and right sides of the picture on Bravo, that is channel 4, on FreeviewHD (UHF) since the first half of last year. This fault is not present on Bravo on Freeview Streaming TV or the +1 channel.

Overscan would hide it. Some TVs don't allow overscan to be turned off on standard definition and when they do they may require it be disabled separately, as is the case on Panasonics and Sonys, so the problem may not be visible for all people.

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#3322284 19-Dec-2024 14:03

Doesn't happen on my Panasonic TVs

fe31nz

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#3322490 19-Dec-2024 22:59

My last MythTV recording from Bravo was on 2024-10-23 and has no problems.

bfginger

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#3354625 17-Mar-2025 15:52

I've seen it on three Panasonic TVs and a Sony.

I recorded the transmission streams of channels 4 and 9 on a Magic TV an hour apart and opened them in VLC. The picture is horizontally squashed on Ch4 Bravo with black bars on the left and right sides.

Apsattv

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#3354646 17-Mar-2025 17:45

What resolution does vlc say? it looks like a scaling issue perhaps bravo isn't in a full "PAL" resolution

RunningMan

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#3354652 17-Mar-2025 18:20

The DVB-S transmission is 720x576. The black bars are within the broadcast frame like this:

Apsattv

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#3354656 17-Mar-2025 18:48

Are you able to upload a .ts sample?

or measure how many pixels those black thin lines are?

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RunningMan

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#3354657 17-Mar-2025 18:53

9 pixels left, 7 pixels right.

Apsattv

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#3354665 17-Mar-2025 19:41

Is that a frame straight out of the recording?
523x288 ????

RunningMan

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#3354668 17-Mar-2025 19:58

That's the OP's image. VLC reports the DVB-S dimensions as 720x576 for both video resolution and buffer. At 720 wide the black bars are 9 / 7 pixels wide as above.

RunningMan

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#3354671 17-Mar-2025 20:04

If you have a DVB-S receiver just tune to Bravo, the black bars are clearly visible each side - had never noticed it but can't unsee it now!

The key is the bars are being added before broadcast - it's not a frame that is 704 wide and the receiver is pillarboxing it. It's a 720 wide picture with 16 pixels of black, which are not uniform left and right.

EDIT: I'm looking at the DVB-S broadcast and OP is looking at DVB-T, so that may give some indication as to where in the process this is happening as both have the same issue.

Spyware

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#3354672 17-Mar-2025 20:12

Bars are on Sky's transmission but don't appear in DVB-T from Sugarloaf on my two Samsung TVs.

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Apsattv

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#3354690 17-Mar-2025 21:06

It must be an encoding error with the input resolution not set correctly. So its filling the sides to fill out the frame.

Someone should let Freeview or Kordia know. I doubt a complaint tro Sky would get anyone anywhere they have enough issues of their own

RunningMan

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#3354692 17-Mar-2025 21:08

Interesting that it doesn't seem to affect all DVB-T locations though. Sugerloaf is OK, but the OP's is not.

Spyware

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#3354695 17-Mar-2025 21:23

P.S. I checked via HDHomerun also and looks as it should with no bars.

bfginger

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#3354709 17-Mar-2025 23:08

Apsattv:

What resolution does vlc say? it looks like a scaling issue perhaps bravo isn't in a full "PAL" resolution

VLC says it's 720x576 for both. The weird thing is it says the "colour transfer function" is BT.709 for 4 and BT.470 for 9.

AFAIK most if not all Samsung and LG TVs don't let you disable overscan on standard definition, so you shouldn't see the bars.

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