Unexpected behaviour using deckink card with gstreamer

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reinismu

  • Posts: 2
  • Joined: Fri Sep 17, 2021 9:26 pm
  • Real Name: Reinis Muiznieks

Unexpected behaviour using deckink card with gstreamer

PostFri Sep 17, 2021 9:32 pm

Hi!

I have been trying to create a simple GStreamer plugin to send data through SDI using decklink card. All has worked well so far except decklink is converting all my 0 bytes to 1 ...

My plugins source code https://github.com/reinismu/gst-data-video

Code: Select all
Got content [{Should be 0 -> } 1, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76, 77, 78, 79, 80, 81, 82, 83, 84, 85, 86, 87, 88, 89, 90, 91, 92, 93, 94, 95, 96, 97, 98, 99, 100, 101, 102, 103, 104, 105, 106, 107, 108, 109, 110, 111, 112, 113, 114, 115, 116, 117, 118, 119, 120, 121, 122, 123, 124, 125, 126, 127, 128, 129, 130, 131, 132, 133, 134, 135, 136, 137, 138, 139, 140, 141, 142, 143, 144, 145, 146, 147, 148, 149, 150, 151, 152, 153, 154, 155, 156, 157, 158, 159, 160, 161, 162, 163, 164, 165, 166, 167, 168, 169, 170, 171, 172, 173, 174, 175, 176, 177, 178, 179, 180, 181, 182, 183, 184, 185, 186, 187, 188, 189, 190, 191, 192, 193, 194, 195, 196, 197, 198, 199, 200, 201, 202, 203, 204, 205, 206, 207, 208, 209, 210, 211, 212, 213, 214, 215, 216, 217, 218, 219, 220, 221, 222, 223, 224, 225, 226, 227, 228, 229, 230, 231, 232, 233, 234, 235, 236, 237, 238, 239, 240, 241, 242, 243, 244, 245, 246, 247, 248, 249, 250, 251, 252, 253, 254, 254, 1, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43]


I use UYVY pixel format. If I launch pipeline without going through decklink card then everything works fine. Has anyone else encountered this issue?

Thanks a lot!
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Cameron Nichols

Blackmagic Design

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Re: Unexpected behaviour using deckink card with gstreamer

PostThu Sep 23, 2021 6:35 am

Hi Reinis,

This is expected - 8-bit values 00h and FFh are prohibited from the active video as they are used for synchronisation in SDI. As such the DeckLink will clamp 00h and FFh values to 01h and FEh respectively.

In any case you should use 8-bit video range - 16 (0% black) to 235 (100% white).

Regards
Cameron
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reinismu

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  • Real Name: Reinis Muiznieks

Re: Unexpected behaviour using deckink card with gstreamer

PostWed Sep 29, 2021 5:33 pm

Thanks!

Didn't even notice 255 missing.

Could you point me to some resource explaining why exactly "16 (0% black) to 235 (100% white)" this range?

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