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 have been removed due to a mistake, they are in the next posts.

[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.

[dellsam34]

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).

I agree, But that's possible the S-Video output is to blame due to the fact that converting back from digital to analog after the TBC incur some loss but HDMI is not because it's fed from the digital out of the digital processing unit, I don't know how signal handling is done inside the HM-DH5U to be honest, But one thing for sure, for this machine the HDMI is much better than S-Video, That's probably how I'm going to use this VCR from now on.

[Sharc]

I agree, But that's possible the S-Video output is to blame due to the fact that converting back from digital to analog after the TBC incur some loss but HDMI is not because it's fed from the digital out of the digital processing unit, I don't know how signal handling is done inside the HM-DH5U to be honest,

I don't think that the extra D/A conversion is to blame for lower sharpness. You did mention that the TBS800 has some DNR which cannot be disabled. I don't know if and how it is inserted into the workflow, possibly affecting the signal. Also, the TBS800 default settings (neutral or midpoint) may compromize the sharpness slightly. Just some thoughts, no proof.
So take the best and leave the rest.....

[dellsam34]

I did compare the TBS800 against other devices before, it does not seem to took duller than the rest, So I highly doubt its DNR is the cause.

The way proc amp works is if you move the slider it will activate the procamp and reset button becomes active, you click on reset it becomes grayed out and all sliders move to their default position which means the procamp is off.

[Sharc]

Taking a second look it appears that the HDMI has elevated darks resulting in lower contrast ("milky" look in comparison with the SDI). This can be easily corrected in post processing though.

Edit: Interleaved comparison attached.
Edit2: Original attachment removed, needs to be IVTCed. Here we go:

[dellsam34]

I've introduced some new workflows for comparison and another VCR, I will include the first two tests here for easy access, order is rearranged:

1- HR-S7600AM --> S-Video to Y-C BNC cable --> S&W TBS800 --> SDI cable --> HyperDeck Shuttle 2 --> Internal SSD recording lossless SD 4:2:2
2- HM-DH5U --> HDMI cable --> HyperDeck Shuttle 2 --> Internal SSD recording lossless SD 4:2:2
3- HM-DH5U --> S-Video to Y-C BNC cable --> BE75 --> SDI cable --> HyperDeck Shuttle 2 --> Internal SSD recording lossless SD 4:2:2
4- HM-DH5U --> S-Video cable --> Miranda ASD-272P --> SDI cable --> HyperDeck Shuttle 2 --> Internal SSD recording lossless SD 4:2:2
5- HM-DH5U --> S-Video cable --> Pinnacle 500-USB --> USB cable --> CaptureFlex recording lossless SD 4:2:2
6- 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

Notes:
The JVC HR-S7600AM is in edit mode, 3R is off, TBC on.
Miranda is a video only S-Video to SDI stick, no audio, it was sent to me by one of the members long time ago for this purpose.

[dellsam34]

I made a huge mistake, I left the chroma slider a little bit above the center from a previous capture for the TBS800, So I removed the files from the original post and posted a corrected recapture in the above post, While at it I've added two more captures for the HM-DH5U-TBS800 combo, one with legalizer checked and one with all the DNR options turned on (see the menu attached), It turns out the legalizer does change something, I noticed it in the sky section of the frame.

[pandy]

One important remark - SDI is unidirectional interface - there is no bidirectional communication there - HDMI is also unidirectional (from Source toward Sink a.k.a receiver) but connection between Sink and Source is established trough EDID communication line and mutual negotiation - based on EDID content stored in HDMI Sink a HDMI Source select best link parameters (what is best is up to Source capabilities and software design choices).

In other words SDI need to be manually configured but usually there is no need to do this - perhaps except selecting some few basic options where HDMI may require more tweaking (like color space selection, quantization range etc) - also there is possibility to "cheat" HDMI Source by modifying EDID communication on the fly (or create EDID different than reported by Sink).

So HDMI may offer theoretically higher flexibility but also may be more sensitive to configuration errors.

[dellsam34]

I'm not sure I'm following you there, Analog to SDI device are FPGA based, they have their own control software as seen in the above screenshot, the whole reason I use them is because they don't rely on computer CPU for converting analog to digital, why would you want to tie them to the computer?

The HDMI from VCR can be used with a HDMI capture card for procamp tweaking but I'm not a big fan of capturing from HDMI.

[pandy]

My point was that HDMI have more options to "broke video" and SDI has less features to "broke video".

[Sharc]

Interesting. I had a quick look at your "legalizer" clip only without really analyzing the video. The "legalizer" appears to have done what it is supposed to do, namely legalizing the captured YUV such that upon conversion to RGB the transformation results in valid and unclipped RGB. Therefore, the sky turns into bluish instad of grey-white, and you see more details and structures in the bright areas like the former mainly flat white parasol.
When I find some time I want to take a closer look to see whether this speculation is right .....
The analog NR has usually 2 effects: On the positive it reduces the noise. On the negative it softens the picture. Typically a compromise.
Also, I am not sure whether the analog pedestal should be enabled. It may just raise the dark level (?). You may just try.

Edit:
Yup, look at this: sigificantly less hot (illegal = marked cyan) pixels than before (post#6), and no luma excursion >235. The legalizer apparently did its job. I would assume that the user manual should describe its function and purpose.

[dellsam34]

Good point about the analog Pedestal, To be honest I have no idea what's its purpose exactly, but when unchecking it, it turns the frame very bright and the blacks grey, Having it on does darken the picture but it doesn't crash the detail in blacks, that's why I like having it on, plus I can always brighten the image using the procamp controls on the left side if I needed to, I could be wrong.

The legalizer should be on then from now on.

The manual doesn't say much, here it is: