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Old 3rd February 2024, 21:06   #1  |  Link
Katie Boundary
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Does "composite" refer specifically to RCA connectors or does it include coaxial?

The wikipedia articles on the subjects seem to have been written by people who think that "composite" is synonymous with "RCA connectors", but descriptions are inconsistent.

EDIT: to clarify, I'm interested in knowing whether dot crawl (checkerboard effect along sharp edges) is exclusive to RCA cables or if coaxial can cause it too.
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Last edited by Katie Boundary; 4th February 2024 at 08:21.
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Old 4th February 2024, 02:47   #2  |  Link
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Quote:
Originally Posted by Katie Boundary View Post
The wikipedia articles on the subjects seem to have been written by people who think that "composite" is synonymous with "RCA connectors", but descriptions are inconsistent.
In the consumer space, "composite" typically refers to a single RCA connection. "Component" will typically refer to three RCA connections of R, G, and B.
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Old 4th February 2024, 08:18   #3  |  Link
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SCART connectors do also carry "composite" video.
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Old 4th February 2024, 08:19   #4  |  Link
Katie Boundary
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Originally Posted by eac3to_mod View Post
Coax can carry composite video.
"Can"? So it sometimes carries other kinds of video?
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Old 4th February 2024, 08:32   #5  |  Link
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Coax cables in general can carry whatevery you want,... (there are used for networking too , which is mentioned over at https://en.wikipedia.org/wiki/Coaxial_cable)
I thing the 'Can' was more a: "It's possible to send composite video data over coaxial cable and the problem isn't the cable, but the composite video,...", but eac3to_mod might clarify.
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Old 4th February 2024, 08:32   #6  |  Link
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"Can"? So it sometimes carries other kinds of video?
Yes, R'G'B' (for studio equipment, BNC connectors)

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Old 4th February 2024, 09:44   #7  |  Link
Katie Boundary
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Coax cables in general can carry whatevery you want,... (there are used for networking too , which is mentioned over at https://en.wikipedia.org/wiki/Coaxial_cable)
I thing the 'Can' was more a: "It's possible to send composite video data over coaxial cable and the problem isn't the cable, but the composite video,...", but eac3to_mod might clarify.
If I want to capture video from some VHS tapes by putting those tapes in a VCR and connecting that VCR to an ATI All-in-Wonder capture card with a coaxial cable, what kind of signal will be sent along that cable, and will it have dot crawl?

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Yes, R'G'B'
???
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Old 4th February 2024, 09:50   #8  |  Link
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???
R'B'G' = gamma corrected RGB. Sometimes the ' are simply omitted.
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Old 4th February 2024, 10:00   #9  |  Link
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Originally Posted by Katie Boundary View Post
If I want to capture video from some VHS tapes by putting those tapes in a VCR and connecting that VCR to an ATI All-in-Wonder capture card with a coaxial cable, what kind of signal will be sent along that cable, and will it have dot crawl?
Composite video is always prone to producing dotcrawl unless you have a perfect Luma/Chroma separating filter switched in.
Use S-Video instead or YPbPr (RGBS) component video. Quality is significantly better than what you will ever get with Composite anyway.
S-Video has Luma and Chroma on separate wires and is usually provided via a Mini-DIN aka Hosiden connector. S-Video is sometimes available/configurable on the SCART connector as well. Depends on the VCR model.

Don't know what interfaces/connectors your VCR and All-in-wonder support. Once this is clarified one can choose from recommended options.

Last edited by Sharc; 4th February 2024 at 10:39.
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Old 4th February 2024, 10:01   #10  |  Link
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"Can"? So it sometimes carries other kinds of video?
Yes - after going into Digital coax cables typically carry SDI as Digital Component (most common 4:2:2 YUV) for SD/HD/UHD. Users can buy HDTV CCTV cams with (HD-)SDI link over single coax cable for example for home.

SDI signalling typically more critical to coax terminating connectors quality (VSWR) but for short distances low frequency SD or even HD may work via RCA cheap connectors too. RCA simply very cheap type of connectors for coax cables and typically used in home endusers AV equipment.

At the Digital HD era the HD over coax using SDI is more expensive so home AV equipment of enduses uses mostly multi-wire HDMI interface for short cabling.

Last edited by DTL; 4th February 2024 at 10:07.
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Old 4th February 2024, 10:14   #11  |  Link
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Like you can see here: https://en.wikipedia.org/wiki/Composite_video the word Composite implies only 1 wire (Shielded or Coaxial) than carry luminance and chrominance.

Whe we use 3 wires (shielded-RCA or coaxial, RedGreenBlue) we call it Component video
Don't mistake with 3 shielded-RCA: Yelow for Composite video, White for Left Audio, Red for Right Audio

To carry high frequencies (video or others) always is better the coaxial (R'G'B' for studio equipment, BNC connectors), after a shielded cable (RCA's) and the worse are the un-shielded, but sometime are used in SCART to carry Component or Composite video.

If you can use S-video conector is better than Composite because carry luminance and chrominance in 2 wires: " It also eliminates several types of visual defects such as dot crawl which commonly occur with composite video"
But your VHS player need that S-video output (or Scart to S-video adapter), and your ATI All-in-Wonder also.
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Old 4th February 2024, 13:42   #12  |  Link
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It's nothing to do with the cable, it's just how the signal is composed. It could be sent through cables, over the air, stored on tape - or even black and white film - or drawn on a piece of paper; it's still composite video.
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Old 8th February 2024, 11:49   #13  |  Link
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Composite video is always prone to producing dotcrawl unless you have a perfect Luma/Chroma separating filter switched in.
Okay but that doesn't answer my question because I still don't know exactly what is or isn't "composite" video.

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Don't know what interfaces/connectors your VCR and All-in-wonder support. Once this is clarified one can choose from recommended options.
Pretend that the VCR only has two outputs: coaxial cable and RCA connectors. I know that the RCA connectors will produce dot crawl. Can I avoid the dot crawl by using the coaxial cable instead?

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Like you can see here: https://en.wikipedia.org/wiki/Composite_video the word Composite implies only 1 wire (Shielded or Coaxial) than carry luminance and chrominance.
But are ALL such signals considered composite? Or are they only considered composite when sent over RCA cables?
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Old 9th February 2024, 00:00   #14  |  Link
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Pretend that the VCR only has two outputs: coaxial cable and RCA connectors. I know that the RCA connectors will produce dot crawl. Can I avoid the dot crawl by using the coaxial cable instead?
The 'coaxial' on your VCR (which model?) may be an RF (antenna) connector for the TV tuner, I suppose.
The yellow RCA carries the Composite video signal which combines luma+chroma+sync on one wire by frequency interleaving - a special form of frequency multiplexing.
For decoding the luma must be separated from the chroma by means of filters (notch or comb filters in the receiving device like in your AIW card (which model?) - check the specs). This separation is however never perfect which produces dotcrawl and rainbows. How much depends on the filter properties. To avoid it you should use a VCR with S-Video output where (luma+sync) and (chroma) are conveyed on 2 separate wires usually via a mini-DIN (aka Hosiden) connector.
So if your VCR has no S-video output but yellow composite RCA only (plus red and white RCA for audio) you may have to live with some residual dotcrawl, depending on the performance of the filters in your capture device (your AIW card).

Last edited by Sharc; 9th February 2024 at 10:08.
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Old 9th February 2024, 11:08   #15  |  Link
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To avoid it you should use a VCR with S-Video output where (luma+sync) and (chroma) are conveyed on 2 separate wires usually via a mini-DIN (aka Hosiden) connector.
The signal on a VHS tape (specified above) is already composite. EDIT: nope it's not.
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Old 9th February 2024, 15:00   #16  |  Link
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But sending the video out on S-Video still helps a lot, no dotcrawl or rainbows.
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Old 9th February 2024, 23:14   #17  |  Link
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The signal on a VHS tape (specified above) is already composite.
The signal on a VHS tape is recorded as Y/C. Separated luma and chroma.
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Old 10th February 2024, 00:15   #18  |  Link
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Heterodyne or "color-under" recording is normally used in consumer recorders (VHS, S-VHS, Video8, Hi8, Betamax). Chroma is mixed down to a subcarrier below the FM-modulated luma signal, hence the "color-under" principle for tape recording. Luma and chroma are separated frequency wise.
Upon playback the recorded color-under chroma is mixed up (heterodyned) to the standard PAL or NTSC color subcarrier. Chroma and luma are still separated and made available on 2 separate wires on the S-video connector. Only after summing of the chroma plus luma (+sync) we get the composite video signal on the yellow RCA plug (or SCART connector).

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Old 11th February 2024, 19:19   #19  |  Link
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But are ALL such signals considered composite?
Composite mean luma and chroma are not separated (combined) and use same time and frequency domain.

Any cable can carry also separated luma and chroma data - like frequency or time domains separated. But it will take more frequency bandwidth.

So composite designed initially to send via Air and use as low frequency bandwidth as possible (really to be compatible with luma only signalling).

So composite is luma data bandwidth with colour data specially encoded to be mixed in the same bandwidth. This cause luma-chroma separation issues at decoders (like that dot-crawls).
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