Quantcast What format do you store your VHS captures in? - digitalFAQ Forum
  #1  
04-12-2020, 03:42 PM
bakerie bakerie is offline
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Just wondering this.

I'm getting 5000-8000kbp/s at 720x576 with H.264 at Q=18, because of how noisy the captures are (this is with quite heavy filtering btw). I remember back many moons ago that people converting these captures used to downsize to 352x288 (for formats like VCD) as it was believed you would capture 90% of the detail in these with a good resizer as there isn't actually that much detail in the image? Is any of this correct?

5 hours records are coming in at nearly 14GBs, so I want to make sure I'm not missing a trick :>
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  #2  
04-12-2020, 04:34 PM
sanlyn sanlyn is offline
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Original captures are on external USB drives as lossless Lagarith YUY2. A few are huffyuv. I don't save all captures.
VHS Restorations are encoded and stored as authored DVD or SD-BluRay on optical disc (2 copies).
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  #3  
04-13-2020, 10:47 AM
msgohan msgohan is offline
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Quote:
Originally Posted by bakerie View Post
I remember back many moons ago that people converting these captures used to downsize to 352x288 (for formats like VCD) as it was believed you would capture 90% of the detail in these with a good resizer as there isn't actually that much detail in the image? Is any of this correct?
352x288 (VCD) is approx. Half-VHS luma resolution. (Half of the vertical info of source is tossed.)

PAL 625-line analog video contains 576 active scanlines per frame. These are discrete; completely separated in the original signal. VHS can't alter this, so it retains full vertical resolution.

The horizontal resolution is where opinions can differ, because in analog there are no "steps" here, just voltage that varies over time in direct relation to represented brightness. This is where the consumer analog tape formats achieve luma bandwidth reduction, to record on smaller and less complex tapes/machines than the studio Production tape formats.

Regardless, VHS is definitely under 352x576 (352x480). These resolutions are called Half-D1. DVD players are required to support them. Blu-ray is not. File-based media player support will vary.

The proper way to convert from 720x576 is to crop 16px total across the image width = 704x576 then resize down to 352x576 (half horizontal) using a good scaler.

One complicating factor is that a digital player showing a 352x576 file may upsize it using a soft filter like Bilinear. In this case, a 352-width file can look less detailed than a 704-width file even though all of the info is there.

Another issue is that you're effectively adding another layer of horizontal chroma subsampling. Many re-samplers in players use Nearest Neighbor, so saturated reds in a 352-width file can look even more blocky than a 704-width file.
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  #4  
04-13-2020, 11:03 AM
sanlyn sanlyn is offline
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Oh. I forgot to mention: Of the lossless VHS captures that I save, they are saved as-is. In my dumber days (which haven't totally ended yet AFAIK) I capped at 640x480, then at 704x480 for a short while, and finally at 720x480 for greater resolution during restoration. Audio was always 16-bit PCM 48Khz.
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  #5  
04-13-2020, 04:50 PM
cbehr91 cbehr91 is offline
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MPEG2 720x480 resolution 18.6mbps video bitrate 320kbps audio bitrate on external USB drives with a backup copy on a DVD. I rarely save the raw captures.
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  #6  
04-16-2020, 02:38 PM
themaster1 themaster1 is offline
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ntsc vhs:
luma-333x480
chroma 40x480

pal vhs:
luma: 335x576
chroma: 40x240 (the vertical chroma resolution of PAL is limited by the PAL color delay line mechanism).

source: wikipedia
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  #7  
04-16-2020, 02:55 PM
bakerie bakerie is offline
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That's really interesting themaster1! So There is 576 lines of info here anyway.

352x576 is a valid DVD resoloution, I wonder is that worth investigating...

Also no wonder VCDs are noticeably blurrier at 352x288
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  #8  
04-16-2020, 03:11 PM
latreche34 latreche34 is offline
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Raw 720x480 NTSC and 720x576 PAL, 10bit HuffYUV 4:2:2 48Khz/16Bit PCM audio on an external HDD, The encoded raw to H.264 flagged for 4/3 aspect ratio, obviously 8bit 4:2:0, 192Kbps/16Bit audio and de-interlaced stored on a separate external HDD.

Personal stuff stored forever. Customer related; raw one month, encoded one year.
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  #9  
04-16-2020, 04:56 PM
msgohan msgohan is offline
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^ 10-bit Huffyuv??

Quote:
Originally Posted by themaster1 View Post
ntsc vhs:
luma-333x480
chroma 40x480

pal vhs:
luma: 335x576
chroma: 40x240 (the vertical chroma resolution of PAL is limited by the PAL color delay line mechanism).

source: wikipedia
Which means take with huge grain of salt, as anyone could have added the info.

The PAL chroma resolution should say 40x288 not 240, since it's a 2:1 line average.
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  #10  
04-16-2020, 10:25 PM
latreche34 latreche34 is offline
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I was forced to down convert to 8bit to save into HuffYUV, But for personal files I use whatever Mediaexpress outputs in 10bit and encode from there.
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  #11  
04-19-2020, 03:53 AM
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lordsmurf lordsmurf is offline
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Quote:
Originally Posted by bakerie View Post
Just wondering this.
I'm getting 5000-8000kbp/s at 720x576 with H.264 at Q=18, because of how noisy the captures are (this is with quite heavy filtering btw). I remember back many moons ago that people converting these captures used to downsize to 352x288 (for formats like VCD) as it was believed you would capture 90% of the detail in these with a good resizer as there isn't actually that much detail in the image? Is any of this correct?
5 hours records are coming in at nearly 14GBs, so I want to make sure I'm not missing a trick :>
That VCD myth was created by people that suck at math, namely those who don't know the different between X and Y axis. The idea was that "240 lines" would perfectly match 352x240 VCD (swap in PAL numbers, but the myth originate NTSC). The NTSC VHS is actually about 240x480 (more accurately 240-300 range, depending on many factors). So 50% data was being lost intraframe + 50% temporal due to deinterlace (then also using terrible lossy methods).

Quote:
Originally Posted by themaster1 View Post
ntsc vhs: luma-333x480, chroma 40x480
pal vhs: luma: 335x576, chroma: 40x240 (the vertical chroma resolution of PAL is limited by the PAL color delay line mechanism).
source: wikipedia
Beware that Wikipedia can be, and often is, just what people write/think, and not actual reliable information. For example, if a Wikipedia entry claimed that VHS (analog) has an exact digital equivalent, then it's nonsense from a moron. Analog and digital have no perfect equivalent, and can never be pixel perfect.

... and I see msgohan beat me to it.

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