From "initial" setup, I was very skeptical of using an SDI capture card with an Analog to SDI converter.
Make no mistake.. setup is (Very) hard.. but the results for Uncompressed UVYV video and Sound are astonishing.
I was also skeptical of whether SONY Vegas Pro could work with SDI for input. It turns out I was right, but there is a work around.
Setting up the Blackmagic Design "mini recorder" SDI to PCIexpress card required I carefully make sure the BIOS of my motherboard had not (turn off) that PCIe slot. I have an older ASUS motherboard which allowed shifting the PCIexpress lanes to concentrate them on longer x4 slots while turning off lanes for other devices like onboard USB ports, or other PCIe slots. the BIOS instructions and in menu directions are a lesson in confusion.. that transcends language barriers.. poor grammar even by the native speaker in Chinese apparently is universal.
As a pre-test with SDI I used the "mini recorder" HDMI input port to capture HDMI video and sound, tha proved difficult first because it only capture sHDCP "free" video which normally is only availabel from a video camera, that supports HDCP "free".. a rare thing these days outside professional broadcast cameras. Game consoles also rarely allow HDCP "free" video to leave their ports. - In the end I used an HDMI and Component cpature box, which when set to Component capture.. actually produced HDMI without HDCP copy protection "free".
Then the version of the Blackmagic Design drivers had to be selected. The earliest is 7.8 however that had severe problems and never produced a picture. Adding to this, Blackmagic installed "two" video drivers;
Blackmagic WDM capture
Decklink Video capture
And decline to explain what each is for in any of their documentation or literature.
Using graphedit and filter exploring it appears the WDM driver is the more universally recognized and compliant for many programs to access the video feeds. The Decklink appears to offer additions pins for control but documentation remains lacking.
The "mini recorder" has an HDMI and an SDI port on the back of the card.
The Blackmagic 7.8 or above driver and media express software "bundle" called "DesktopVideo" also includes a "port management" program that shows up in the Control Panel in Windows or as a separate application installed in the same folder as the media express capture program.
Whichever way you get to the program, you have to select the port to switch it to HDMI or SDI for input before tackling using the card with a capture program.
Finally I had to learn by trial and error which version of DesktopVideo was compatible with my Windows 7 system since it went unsupported by Microsoft in Jan 2020.. however Blackmagic has a habit of de-supporting at any time.. sometimes in versions released years in the past.. so its a major "Hunt" to find the version that works with your version of the Windows operating system.. add to this.. that DesktopVideo "the bundle" adds and removes hardware support for Blackmagic products as a moving target as well.. So you have to track version of operating system, version of DesktopVideo, and version of DesktopVideo which supports your hardware.
Once all these variables are sorted out, and you have a good single that isn't blocked with just an uninformative black screen.. then you have to configure your "mini recorder" capture card to match the type and speed of video signal being input and configure your capture software to use either the WDM driver or the Decklink driver.
It "seems" Decklink is rarely used by any video capture software other than that made by Blackmagic.. that is the "media express" capture software. Almost all others prefer or will only work with the WDM driver.
Sometime after the very first 7.8 driver release Blackmagic also began bundling in a separate Line Input (Blackmagic audio) device driver.. which works in Windows 7. Sometimes programs like OBS Studio can pull sound off the capture device.. sometimes not, and more often its unreliable.. probably since there are so few documents on the WDM driver and Decklink driver.
VirtualDub 1.9.11, OBS, VLC , MPC-HC, AMCap, SONY Vegas 11, 13
The Blackmagic Design "Converter" used was the "Analog to SDI" box.. which is the only New box I have been able to find that advertises as compatible with capturing VHS player video content.
The SD-SDI standard has been around sine 1986, but discouraged or kept mostly out the hands of consumers based on price, complexity and its dependence on mostly Unencrypted video signals.
SDI was perfect adequate for single cable audio and video over long runs in the home, however the HDMI standard was pursued instead to layer on encryption and to support other layered standards.. much like IEEE1394/Firewire was "intended" but never really materialized.. in the end its just a consumer industry "approved" copyright protected physical cable format.
The major advantage over other analog uncompressed capture methods isthe SDI chip "embeds" the audio along with the video in the SDI digital format. Often offset by a deviation that is labeled at 1-2.5 frames.
The key to getting uncompressed SDI video capture working with SONY Vegas Pro for me was choosing to use the Capture "DV" instead of the "HDV or SDI" choice. The Vidcap program then loads and connects to the "mini recorder" over the WDM driver instead of the Decklink driver. Audio similarly connects to the Blackmagic line input device.
It appears the Vegas 14 version may have "fixed" the Decklink problem, but that is an older version that I do not have access to at this time.
Curiously the PowerDirector 10 does not appear to work with even the WDM driver.