VHS dropped frames with Blackmagic?

[Roixos]

Hi everyone,

I’m working on digitizing and upscaling old PAL VHS tapes to HD, but I’m encountering dropped frames where both video and audio cut out completely while the tape continues playing. OBS does not flag these dropouts under "Dropped Frames" in its stats, which is confusing. The image quality is good, but at irregular intervals, the screen goes black – sometimes for a split second, sometimes longer. There are no "No Signal" warnings, just black.

My Setup:
Player: Panasonic NV-FS200 HQ (S-VHS with built-in Line TBC).

Signal Chain:
Player (S-Video) → Y/C Splitter → Blackmagic Analog-to-SDI → SDI Cable → UpDownCrossHD → HDMI → Elgato Cam Link 4K → OBS

Analog Path:
S-Video output → Y/C Splitter (chroma/luma to Cinch).
Blackmagic Analog-to-SDI Converter (DIP switches 3,4,5 = ON → 3G Level A, S-Video/Composite mode).
SDI Cable (1m, 3G/6G 1364A Belden) → Blackmagic UpDownCrossHD (tested modes: 720p50, 1080p25, 625i50 PAL).

Digital Path:
4. HDMI out → Elgato Cam Link 4K → PC (OBS Studio).
Software: OBS Studio (recording: 50 FPS, NVENC HEVC, saved to a dedicated internal SSD).

What I’ve Already Tried:
Checks:
-Swapped cables (SDI, HDMI, S-Video).
-Tested a cheap USB capture device (worked smoothly but with lower quality → rules out player, tapes, or PC as root causes).
-Used both Elgato software and OBS → same issue.
-DIP Switch Variations: Tested multiple configurations on both Blackmagic converters.

OBS Settings:
-Framerate toggling (50/25 FPS).
-Interlacing (Yadif 2x, disabled).
-Encoding tweaks (quality vs. speed, NVENC vs. software encoder).
-Changed recording directory (secondary SSD).

More Info:
-Original Blackmagic adapters (no third-party PSUs).
-Analog-to-SDI converter’s LED only blinks during fast-forward/rewind, not during dropouts.
-Occurs with all tested tapes.

Current Theories & Questions:
Sync Issues:
The Panasonic’s Line TBC might struggle to stabilize the signal for SDI processing. Dould the Line TBC’s sync be incompatible with the Blackmagic converters?

Frame TBC Necessity:
After my testing, I think I’ve ruled out power issues and my PC hardware.

My fear: The Line TBC might not be enough, and a full-frame TBC is required for SDI stability. I already came across a couple related Posts like this one : https://forum.blackmagicdesign.com/v...p?f=3&t=154851
I’d prefer to avoid buying one unless absolutely necessary, but if it’s unavoidable:
What’s the minimum viable TBC that can stabilize SDI signals? The quality is fine, i just need smooth playback.
I’m still really hoping I’ve overlooked a setting or workflow tweak. If not, what’s the most cost-effective frame TBC that pairs with SDI digitization? Or are there alternative sync/stabilization tricks for Blackmagic converters?

Do you have any advice on how to proceed? Perhaps exploring a completely different, more cost-effective option that still delivers similar image quality?

Thanks in advance – some input could save me from a pricey rabbit hole!

[lordsmurf]

Lack of frame TBC is the primary issue.

Blackmagic is not ideal -- but when it fails (which is often), it's almost always due to lack of frame TBC.

OBS is also terrible software for analog videotape capturing. It's digital streaming recording software that "also does" analog ingest/capture, but in a round-about way. The video is recorded from within display layers, rather than direct tapping into the card drivers.

VirtualDub is suggested. However, it also necessitates capturing SD as SD, which you should be doing anyway. Trying to capture SD interlaced as HD progressive makes a mess of interlace and resolution. Proper HD upscale should be carefully done post-capture, in software like Avisynth (even craptastic Topaz), not "on the fly" in capture.

But regardless of HD, or SD, lack of frame TBC will always be a problem.

You need a frame TBC.

Line TBC is "not enough", but rather the wrong tool here. Line TBCs operate in-frame on the image, and dropped frames happen from frame-to-frame (interframe) timing. It's like trying to use a screwdriver to whack a nail, or smack a screw with a hammer. Wrong tool. It makes a mess, or just does not work, or both.

We all want to avoid buying stuff. I tried to avoid buying TBCs years/decades ago. I was so stupid for trying. All I did was frustrate myself, and make my output quality look like crap. Learn from my mistakes.

The entire reason that I have hardware in the marketplace is to make this process easier for everybody. These are the tools we need for this task, no way to avoid it.

[aramkolt]

The FS200 my understanding is the PAL equivalent of the AG1980, so that should put out a pretty decent signal with the TBC on, but yeah, the Blackmagic Analog to SDI doesn't have a frame TBC of any type and what you are describing is what would prompt the need for a frame TBC if you want to keep the rest of the capture chain the same.

I would be surprised if the FS200 plus the GV-USB2 gave any significant dropped frames even if captured with OBS, or you could go the recommended route and capture with something like virtualdub or amarecTV. I've done very limited testing with capture from an AG1980 and a GV-USB2, but there was no appreciable frame drops for the content I tested with Virtualdub.

If you're going the SDI route though, you could just get a TBC that has SDI output and forego the analog to SDI card as that has no TBC. Often times, TBCs with SDI outputs can also upscale. The AJA FS1 would be the other one that Isn't particularly hard to find at least in the USA, though not sure if they are common in PAL-land or not. I can't say those will work with all VCRs, but at least for the AG1980 with the frame TBC on, I haven't seen dropped frames or had issues during my admittedly limited testing so far. The FS1 sometimes doesn't like certain VCR blue screens, but the AG1980 has no blue screen, so that's not an issue there.

Generally I'd say skip the upscaling during capture and do that later unless there's some reason that you really need to do it in a single step. Another issue you could run into is that the Elgato Camlink 4K might not be able to capture interlaced SDI if you do go that route, so you may need a different capture card anyway if you want to do that.

Probably depends on your source content as well if the FS1 will work for you or not, but seems you need some type of frame TBC based on the issues you are describing.

[lordsmurf]

Quote:

Originally Posted by aramkolt

The FS200 my understanding is the PAL equivalent of the AG1980

Sort of. There's always been disagreement on the NV-FS200 and NV-HS1000 vs. the AG-1970 and AG-1980P. To me, the HS1000 lacks DOC, and is really more like the 1970. I need to acquire an FS200 again, for side-by-side comparisons.

Quote:

I would be surprised if the FS200 plus the GV-USB2 gave any significant dropped frames even if captured with OBS,

There is nothing special about the GV-USB2, and it dropped frames lke anything else. Lack of TBC is not solved by a capture card without a TBC.

Quote:

If you're going the SDI route though, you could just get a TBC that has SDI output

In terms of TBCs made for SD analog consumer formats, those really do not exist. (There was a very limited production run of BV, but probably 99% of them are not SDI out. I actually have a few, but not parting with any right now.)

Quote:

The AJA FS1
I can't say those will work with all VCRs
my admittedly limited testing so far

That's a broadcast rackmount unit, not designed for consumer sources like VHS. You'll see the problems eventually, with even modest testing of standard sources.

Quote:

The FS1 sometimes doesn't like certain VCR blue screens, but the AG1980 has no blue screen, so that's not an issue there.

In almost all instance, this is a bad sign. (All rules have exceptions. Certain latter "green era" Cypress are exceptions. The "black era" have similar issues, and are NOT exceptions. Nuance.)

Quote:

Generally I'd say skip the upscaling during capture and do that later

Yep.

Quote:

but seems you need some type of frame TBC based on the issues you are describing.

Yep, very standard issue here.