Capturing Still Frames from interlaced source

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shrecicek

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  • Joined: Tue Apr 02, 2019 11:34 am
  • Real Name: Martin Ferletjak

Capturing Still Frames from interlaced source

PostTue Apr 02, 2019 12:32 pm

Hello, I am trying to capture still frame with DeckLink Mini Recorder using provided API and samples. Everything was OK while developing the app and using HDMI input with 1080p30 but after connecting 1080i50 input to SDI I can see distorted image (I'm quite new to video/capture etc. development so if I understand it correctly, it is the interlacing). Is there some parameter that can be set to capture the image/frame deinterlaced (and if I understand this correctly, it is not possible because it is actually a 'feature' of the capture to be done that way) or is it a matter of postprocessing by software? Can someone suggest a solution/good library for that? Thanks in advance. (image example attached)
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interlaced_capture.jpeg
example of frame
interlaced_capture.jpeg (84.72 KiB) Viewed 850 times
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Jonas Hermansson

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Re: Capturing Still Frames from interlaced source

PostThu Apr 04, 2019 12:28 am

It is indeed caused by your interlaced source, and I am not aware of any function in the BMD API that will provide de-interlaced frames for you.

There are some examples of de-interlacing code if you search on internet, but the problem is that good de-interlacing is a complex process. The pixels you need for your still frame does not exixt, and they will have to calcluated. The quality of the resulting picture is directly depending on how good the process is.
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shrecicek

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  • Real Name: Martin Ferletjak

Re: Capturing Still Frames from interlaced source

PostWed Apr 10, 2019 1:34 pm

Jonas Hermansson wrote:It is indeed caused by your interlaced source, and I am not aware of any function in the BMD API that will provide de-interlaced frames for you.

There are some examples of de-interlacing code if you search on internet, but the problem is that good de-interlacing is a complex process. The pixels you need for your still frame does not exixt, and they will have to calcluated. The quality of the resulting picture is directly depending on how good the process is.


Thank you for your answer, I have searched the code samples and of course found some but as you said, it's complex. But I realized that it is not absolutely necessary to retain full resolution of raw frame and usually the frame is resized (and compressed) to also save disk space so I'll just skip the lines... The results are great for this purpose, and captures are crystal clear (and with more than enough vertical resolution even with skipped lines so no drama there...).

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