Re-Interlacing Bob Deinterlaced 480p
Let’s say you’ve decided you want to digitize analog video, like a home movie. And after watching my video about scaling home movies to 4K, you saw the example at 31:18 and thought: “Okay, the RetroTINK’s do an awesome…
Let’s say you’ve decided you want to digitize analog video, like a home movie. And after watching my video about scaling home movies to 4K, you saw the example at 31:18 and thought: “Okay, the RetroTINK’s do an awesome job for most HD tape transfer but I have some footage that’s really important to me – I want to take all the extra steps to get the best capture in its original 480i format and scale it with software”…plus be able to re-scale it in the future as more methods evolve.
You then check your capture card as shown in the video and realize yours can’t capture interlaced video – It automatically deinterlaces all 480i content to 480p. So what do you do now? Spend lots of time and money on a VHS Decode/Domesday RF setup for the absolute best capture? Buy a Magewell USB card than can handle 480i? Use a Live Gamer 4K with the correct driver? Or do you try to skip a RetroTINK altogether, buy an $80 USB analog video capture card…and then try to hunt down a used Time Base Corrector on eBay and hope it still works?
Or would you rather first try something completely free, that anyone with a RetroTINK 5x/6x/4K can do with any capture card that can accept lossless (RGB24) 720x480p video?
The TINK side is easy: Load up the VHS-to-HD profile, then set the RetroTINK’s output to 480p. Then set deinterlacing to “bob”. This will play back the 60-field-per-second (for NTSC) file, with each field being sent to it’s own frame. Nothing is “scaled” or changed, it essentially just deinterlaces by separating each field to its own frame. Then capture that signal as 480p60 lossless.
After that, you should be able to run an FFMPEG command that “re-interlaces” that file to 480i, allowing you to archive in it’s original format. That would let you scale it the same as if your capture card could just handle direct 480i interlaced capture.
Of course you don’t need to do this with all your old tapes, just the most important memories that are worth the extra effort. Before I go any further, please note that there are a potentially few major issues with this:
- First, even if you painstakingly set up a proper 480p60, bob deinterlaced capture, magnetic tape media might have so many blips and dropouts that even with a solid TBC, the file might be too inconsistent to revert properly. The longest tape I tested was only about 5 minutes and while that worked perfectly, your results may vary.
- Even if the file is 480p60, this will only work (well) if it was bob deinterlaced, as motion adaptive deinterlacing blends the fields together; As seen in the example below, this results is a much softer image and probably isn’t worth doing.
- If you’re working with an existing 480p capture someone sent you, it’s probably 480p30 with every other field dropped. Sadly, there’s no fixing those.
- …and of course, you’ll still need to follow the guides to get a lossless 480p capture for the best results. That’s MUCH easier than 1080p lossless, but still is a learning curve.
So when this question came up in a recent Q&A, I asked Dan Mons his thoughts and he showed me an example of how FFMPEG can do exactly that, resulting in a lossless FFMPEG file! It does require using (gasp!) the command line, but you can just copy and paste everything, changing only the “filename.extension”. So, assuming you understood everything typed above (it’s a lot, I know), let’s get started…
FFMPEG
This method requires FFMPEG. You’ll need to check if it’s installed on your computer before proceeding. To do so, open a Windows command prompt and type: ffmpeg -version
If it shows ffmpeg is already installed, you can move onto trimming. If you get a message like the one below, you’ll need to install it.
The easiest way to install FFMPEG is to, open Powershell and paste this command: winget install -e –id Gyan.FFmpeg
Then just accept the agreements and let it finish the installation. You may have to reboot, but it should just work after.
Trim A Clip
Next, cut a small portion of the file with VirtualDub to run a test conversion. Make sure to use Direct Stream Capture, so it doesn’t change the file at all.
Using a short, trimmed clip will allow you to very quickly generate two files to test the field order, as well as see if the process can work at all on your files.
If you’re not sure how to trim, or would prefer a visual example, please reference the video below’s “Trimming” section at 15:04.
Run The Command
Use the command prompt to navigate to the folder the trimmed file is located. I usually name it something short like “trim.avi” and put it in C:\temp to make navigating the command prompt easier.
Then, copy and paste the code below, changing only the input file name to match your trimmed file – For testing, do this once for each of the two commands:
Top Field First (TFF): ffmpeg -i INPUTFILE.AVI -vf “tinterlace=mode=interleave_top” -c:v ffv1 -level 3 TFFOUTPUT.mov
Bottom Field First (BFF): ffmpeg -i INPUTFILE.AVI -vf “tinterlace=mode=interleave_bottom” -c:v ffv1 -level 3 BFFOUTPUT.mov
Checking The Output File
Now open the TFF file you just created in VirtualDub and go to Video\Filters. Hit Add and select Deinterlace. Leave the default Yadif on the left, then select “Double Frame Rate \ Top Field First” on the right.
Make sure the Pane Layout is showing both panes and move forward one frame at a time. If you see each field as a separate frame in the window on the right and it’s in the right order, it worked and is TFF.
If you see something different each time you advance by one frame, but the image seems to be jumping back and forth, try selecting “Double Frame Rate \ Bottom Field First” instead from the deinterlacing menu. Maybe just do that anyway to verify the difference.
Also check the BFF file with the same methods. This will let you determine if the 480p file can even be properly reverted to 480i, 60 fields per second, as well as what the field order is. For RetroTINK captures, it’s almost always TFF, but double checking is super quick, so it’s worth it.
Final Results
So, even if the field order is correct and it technically worked, how does it actually look? I ran a test using the RetroTINK 4K and you can see the results in the video below: When I used Bob Deinterlacing, it appeared to look just like the raw 480i file, after they were both scaling the exact same way. That said (as expected) things looked a bit soft and weird when I set the TINK to motion adaptive deinterlacing.
Conclusion
So as I’ve “warned” many times in this post: This “re-interlacing bob 480p” method SEEMS to work fine, but I’m not sure how this method would hold up after capturing an entire tape. At least there’s an option available for someone with a RetroTINK, but no access to a capture card that can capture interlaced video (which is most people).
And while you can give it a try on random files people may have sent you, keep realistic expectations for those – It’s probably going to look worse. It’s worth checking on a short clip from the file though: Try scaling the source file to 4K first. Then use this method to re-interlace to 480i, then run a process similar to what I show below to deinterlace using QTGMC. Then scale that file to 4K – Whatever looks better is the right choice.
This video is super long and boring, but if any of this is confusing to you, it should clear things up:
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