HDMI vs. SDI Analog Tape Video Capture

[dellsam34]

I was asked numerous times to compare analog video capture such as VHS between two methods, SDI and HDMI, Although I have the JVC HM-DH5U a NTSC VHS/S-VHS/D-VHS machine that has both S-Video and HDMI outputs for quite some time now but I've never had a proper HDMI capture device or card until now, I recently acquired the Black Magic HyperDeck Shuttle 2 a SDI and HDMI recorder and I thought this is the perfect time to do such a test, So here it is:

How the test was done?
I played back this VHS tape "The adventure of the young Indiana Jones" and captured the exact same segment with both methods, The HD-DH5U outputs the signal on both S-Video and HDMI at the same time which makes the process quick and easy, The tape by the way has Macrovision so this gave me an opportunity to test the HyperDeck if it ignores it, and it seems that it does.

The workflows are as follows:
HM-DH5U --> S-Video to Y-C BNC cable --> S&W TBS800 --> SDI cable --> HyperDeck Shuttle 2 --> Internal SSD recording lossless SD 4:2:2
HM-DH5U --> HDMI cable --> HyperDeck Shuttle 2 --> Internal SSD recording lossless SD 4:2:2

Notes:
- VCR settings for both workflows are the same, Edit, Video stabilizer off, line TBC cannot be turned off in this VCR.
- TBS800's proc amp setting are all at neutral or mid point, Audio gain is slightly higher in the TBS800 because I forgot to reset it from a previous capture job, but it shouldn't matter, The TBC is set to "free run" to lock the audio to the video.
- There is no setting for the HyperDeck, it just saves whatever comes in to the SSD.

Took each of the two files into vdub2 to output HuffYUV, Make accurate trimming at the exact same frames and remove the 14 blank audio channels.

The files:

[themaster1]

So your conclusion/observation are ?

[lollo]

Thanks for the excellent comparison, much appreciated! A lot of incentives to work on it!

I am in rush, so I just can do a quick check on the 2 segments.

The SDI capture has clipped whites:



Initially I had a very small preference to the SDI captures because the overall look, but once the levels are equalized they looks very similar to me, with a small preference for the HDMI capture in term of details (just speculating).

https://imgsli.com/MzEyNzAy

https://imgsli.com/MzEyNzAz

Basically, we are comparing here the quality of the A/D conversion of the S&W TBS800 versus the HM-DH5U (and both look nice) together with any degradation in the signal path because the standard (no evidence of that, obviously).

I will perform some more test on my side in the next days, thanks again for the material you provided!

v1=AviSource("VCR-TBS800-SDI.avi").convertToRGB().crop(0,0,-1,0).addborders(1,0,0,0).crop(8,10,-10,-10).convertToYUY2()\
#.convertToYV16().histogram("levels")
v2=AviSource("VCR-HDMI.avi").crop(0,0,0,-4).addborders(0,4,0,0).crop(8,10,-10,-10)\
.colorYUV(off_y=-27, gain_y=20)\
#.convertToYV16().histogram("levels")

#return(v1)
#return(v2)

#interleave(\
#stackhorizontal(\
#stackvertical(\
interleave(\
subtitle(v1,"VCR-TBS800-SDI.avi",size=20,align=2),\
subtitle(v2,"VCR-HDMI.avi",size=20,align=2)\
)

[dellsam34]

So your conclusion/observation are ?

It's up to you or anyone how to interpret the differences, I just made the files.

[dellsam34]

I forgot to mention that the TBS800 has some sort of digital DNR built in that cannot be turned off, It does however have an option for analog NR and chroma NR which are turned off, It also has a check box for legalizer, It doesn't appear to make a difference when checked.

[Sharc]

Both extend the brights beyond luma 235, the HDMI just a bit less than the SDI. Neither is severely clipped though, so that's no problem as long as one stays in YUV.
However, upon importing these YUV captures into certain NLEs (including Vdub) or applying certain filters the YUV may be converted to RGB which get clipped for the Rec.601 matrix, means loosing fine details irreversibly in those brights.
The screenshot shows the "hot" pixels (in good approximation) for the HDMI in Cyan. (Much the same for the SDI.)
Apart from this the 2 methods are pretty much equivalent IMO.