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BM Shuttle Intensity interlacing field issues
I have two possibly related questions about interlacing issues with the VHS stuff I’ve been capturing.
I’m using a Blackmagic Shuttle Intensity Thunderbolt, and I’m somewhat frequently getting portions of video where one field will remain stuck, while the other field continues to play on sometimes for several seconds. I’m using an AVT-8710 TBC between the Shuttle and the VCR, and on some of the more troublesome tapes, I’ve had to engage the VCR’s “video calibration” feature (it’s a JVC HR-S4600U) to keep the signal from completely cutting out. Everything is hooked up via S-Video, although most of the tapes have been plain old VHS rather than S-VHS. I should also note everything is NTSC, and are primarily home-recorded or modest studio-dubbed tapes rather than anything professionally manufactured.
I’d been chalking this lagging field effect up to the tapes just being that far gone, and the TBC kicking in to correct it. Is this generally how that process should look?
Or is this some sort of field order issue? Thus far I had been capturing as 8-bit AVI YUV, however just out of curiosity, today I tried Media Express’s AVI Motion JPEG setting. Mediainfo told me the resulting video was upper field first. I had been assuming everything prior to today was lower field first, as that’s how Premiere seemed to interpret it. Mediainfo doesn’t have anything to say on the 8-bit BM codec AVIs field order unfortunately. Have I been doing things literally backward all along, or does the Shuttle capture BM codec stuff as lower, and MJPEG as upper?
Thanks in advance!
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3 Replies
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Field order can be different depending on the capture device. Typically, HD is upper first and SD is lower first.
The “Stuck field” problem is a digital issue and analog tape can’t cause that. I’m sure if you monitor the output of your Shuttle composite or S video on a tv, it will show the same problem. Are you working with SD or HD video and are you using Media Express to play or an NLE?
I gather you’re on a Mac since it’s a thunderbolt device. I have the USB3 Shuttle on a PC and have not seen issues like that. I put a Solid State drive in one of my laptops and can capture HD MJPEG, 8 bit AVI and even 10 bit uncompressed avi without any problems. Although I have never had the need to use the sd outputs of my shuttle.https://www.provideocoalition.com/field_order
Danny Hays
Samples of my Work can be seen here:
https://www.youtube.com/user/ErnestDaniels/videos -
I’m only working with SD stuff, so like you say, I’d expect everything to be lower field first. I’m actually on a PC with an oddball motherboard that supports Thunderbolt. I’ve been capturing right into Media Express, and haven’t actually set up an SD monitor. I’ll see what I can do with that. Now the TBC I have claims to be full frame, so does that mean it couldn’t be causing this lagging field issue?
I tried running my allegedly top field first MJPEG capture through an ffmpeg script that’s supposed to determine field order by comparing frames, and it’s telling me it’s lower field first. Could Media Express just be flagging interlaced MJPEGs incorrectly?
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Monitoring the S video out of the shuttle will tell you if it’s the TBC causing it. Won’t the person using the tape need one between their VCR and digital switcher anyway? As far as if it’s a field order or not I’m not knowledgeable enough on that subject as I use progressive HD and convert any interlaced video to that. I don’t like the way interlaced video looks.
Danny Hays
Samples of my Work can be seen here:
https://www.youtube.com/user/ErnestDaniels/videos
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