NTSC VHS newbie summary #5: Resolution mp4 creation & upscaling

[brockway]

I've spent the past year slowly plugging away at capturing some NTSC VHS tapes. I had to create notes to keep things straight, so I thought I'd share them in case they help others. I'm a newbie. Not an expert. These are not comprehensive. Take them for what they are.

Here is what I used in my setup: JVC SVHS HR-S2913U > DMR-ES15 > Pinnacle 710 USB > Windows 10 > Virtual Dub 1.9.11 .

NTSC VHS newbie overall summary: Capturing
NTSC VHS newbie overall summary: Processing & Conversion

NTSC VHS newbie summary #5: Resolution for upscaling & mp4 creation

After my NTSC VHS footage was captured, I needed to learn more about resolutions before creating mp4s and/or upscaling.

Here's an intro to DAR, SAR & PAR.

DAR: The true resolution of VHS is 4:3 scale, otherwise known as Display Aspect Ratio (DAR).

SAR: However, NTSC VHS is best captured at 720x480, which is a stretched 3:2 scale. This is known as the Storage Aspect Ratio (SAR). In this case the SAR is 3:2 (720/480 = 3/2 = 1.5).

But, NSTC VHS footage captured at 720x480 includes 8 extra lines of black to right & left of capture. Removing the 16 extra vertical lines, gives 704x480. So the actual NTSC VHS footage has a SAR of 1.46666 (704/480)

PAR: The Pixel Aspect Ratio (PAR) describes the shape of the pixels that are stored for the image.

• When the PAR is 1:1 the pixels are square and represent the true shape of the image.
• Note: SAR x PAR = DAR or PAR = DAR/SAR
• Essentially, pixels are square when the DAR and SAR are the same.
• Also note that PAR is sometimes referred to as Sample Aspect Ratio (a 2nd different SAR)

For captured NTSC VHS cropped to 704x480, the capture is stretched with a PAR of 10/11 since SAR is 1.4666 (704/480) and DAR is 1.333 (4/3). (PAR = DAR/SAR = 1.333 / 1.4666)

Recommended approach: Display devices will display 704x480 at the proper 4:3 VHS scale when the media file specifies the DAR of 4/3. When converting a captured AVI to MP4, this can be accomplished by setting the PAR appropriately to 10/11. This is the recommended approach for analog NTSC VHS video as it eliminates the extra black on left & right side.

For example, in Hybrid when converting to MP4, under crop/resize, select: Convert output to PAR: "MP4 NTSC 4:3 (10/11)" and crop 8 from each side (giving 704x480 resolution).

Alternatively, the footage doesn't need to be cropped and can remain 720x480 NTSC VHS, in which case the PAR needs to be set to 8:9 when converting to MP4.

From latrech34: Here are the PAR values for the 4:3 frame:
http://www.digitalfaq.com/forum/video-restore/12401-upscaling-ntsc-vhs.html#post81696

NTSC:
720x480 (DV/DVD, Full frame) -> SAR=8/9
704x480 (Analog Capture, SD Crop) -> SAR=10/11
640x480 (Square pixel, SD Resize) -> SAR=1

PAL/SECAM:
720x576 (DV/DVD, Full frame) -> SAR=16/15
704x576 (Analog Capture, SD Crop) -> SAR=12/11
768x576 (Square pixel, SD Resize) -> SAR=1


Upscaling to 1080p:
latreche34: When upscaling 720x480 VHS capture, it is best to crop the 8 lines on both sides of the capture and resize to 1440x1080. This gives a DAR of 4:3 and square pixels.
Source: http://www.digitalfaq.com/forum/video-restore/12401-upscaling-ntsc-vhs.html#post81675


These are helpful links:
https://forum.videohelp.com/threads/392580-How-to-properly-adjust-aspect-ratio-when-co...VHS-to-digital
https://forum.videohelp.com/threads/312656-Can-someone-EXPLAIN-the-whole-720x480-thing-to-me
https://en.wikipedia.org/wiki/Pixel_aspect_ratio