Sync Signal for YCbCr video - Electronic Circuits Projects Diagrams Free

FusionITR · 6th July 2006, 01:46 PM

I know that the luma (Y) sigal carries the sync signal, but what ratio of the sync signal is in the Y signal?

Ive seen schematics that indicate that the Y signal is 0.7Vpp + 0.3Vpp of sync, but I have not seen this documented anywhere. Can anybody confirm this or point me to any documentation they can find?

Thanks.

HiTech · 6th July 2006, 02:52 PM

You are correct that the Y signal is 0.7Vpp + 0.3Vpp of sync and hopefully the photos below show the proof you ask for:

FusionITR · 6th July 2006, 04:18 PM

Thanks a lot! Where did you get that information and those graphs?

I'm looking for documentation that describes, in detail, all information about R G B/Sync video standard, with graphs like the ones above. Also information about NTSC composite and S-Video.

HiTech · 6th July 2006, 07:02 PM

Just use your web browser!!

http://www.seanet.com/~bradford/ntscvideo.html

http://www.kat5.tv/videoformats.html

http://www.maxim-ic.com/appnotes.cfm...te_number/1184

http://www.iway.co.nz/body.php?page=...nectorsSignals

FusionITR · 6th July 2006, 09:53 PM

Hmm, ok given that I have a 5V TTL composite sync, and Y requires 0.299R + 0.587G + 0.114B, can I just voltage divide the 5V TTL sync down to 1V then -0.3Sync from the equation from Y?

I hope that question made sense.

HiTech · 7th July 2006, 01:19 PM

I don't fully understand that 5v "composite" sync thing. Composite refers to the entire video signal and ALL of its components. When you reduce sync levels, you reduce "lock" or stabilization of video on a tv/monitor. It sounds plausible what you suggest but verification of the required levels may need the use of a waveform monitor and vectorscope to verify those levels are indeed accurate. You can do the math and theory to select component values, but tolerances may affect the overall outcome.

FusionITR · 7th July 2006, 02:16 PM

Quote:

Originally Posted by HiTech

I don't fully understand that 5v "composite" sync thing. Composite refers to the entire video signal and ALL of its components. When you reduce sync levels, you reduce "lock" or stabilization of video on a tv/monitor. It sounds plausible what you suggest but verification of the required levels may need the use of a waveform monitor and vectorscope to verify those levels are indeed accurate. You can do the math and theory to select component values, but tolerances may affect the overall outcome.

Composite Video and Composite Sync are two different things.

Theres different types of video stablization, Horizontal/Vertical Sync, Composite Sync (combined H/V Sync in one signal), and Sync on Green.

http://www.christiedigital.com/proje...ry/index.asp#C

Quote:

Composite sync
A signal combining horizontal and vertical sync pulses, and equalizing pulses, with no picture information and no signal reference level. Composite sync is sometimes referred to as "C", "S" (as in RGBS) or "HV" (as on some connector panels).

Composite Sync is 5V TTL driven, unlike Sync on Green type of Sync, which is -0.3Vp after a green scanline is drawn (or in the case of component video, the Y).

Composite Video, as you know, is luma, chroma, and sync all combined in one signal (the sync type in composite video is a Sync on Green type sync).

So as you see, Composite Sync and Composite Video are two very different things.

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6th July 2006, 01:46 PM	(permalink)
FusionITR	Sync Signal for YCbCr video I know that the luma (Y) sigal carries the sync signal, but what ratio of the sync signal is in the Y signal? Ive seen schematics that indicate that the Y signal is 0.7Vpp + 0.3Vpp of sync, but I have not seen this documented anywhere. Can anybody confirm this or point me to any documentation they can find? Thanks.

6th July 2006, 02:52 PM	(permalink)
HiTech	You are correct that the Y signal is 0.7Vpp + 0.3Vpp of sync and hopefully the photos below show the proof you ask for: __________________ Don't make me reach through this monitor to slap you a good one!

6th July 2006, 04:18 PM	(permalink)
FusionITR	Thanks a lot! Where did you get that information and those graphs? I'm looking for documentation that describes, in detail, all information about R G B/Sync video standard, with graphs like the ones above. Also information about NTSC composite and S-Video.

6th July 2006, 07:02 PM	(permalink)
HiTech	Just use your web browser!! http://www.seanet.com/~bradford/ntscvideo.html http://www.kat5.tv/videoformats.html http://www.maxim-ic.com/appnotes.cfm...te_number/1184 http://www.iway.co.nz/body.php?page=...nectorsSignals __________________ Don't make me reach through this monitor to slap you a good one!

6th July 2006, 09:53 PM	(permalink)
FusionITR	Hmm, ok given that I have a 5V TTL composite sync, and Y requires 0.299R + 0.587G + 0.114B, can I just voltage divide the 5V TTL sync down to 1V then -0.3Sync from the equation from Y? I hope that question made sense.

7th July 2006, 01:19 PM	(permalink)
HiTech	I don't fully understand that 5v "composite" sync thing. Composite refers to the entire video signal and ALL of its components. When you reduce sync levels, you reduce "lock" or stabilization of video on a tv/monitor. It sounds plausible what you suggest but verification of the required levels may need the use of a waveform monitor and vectorscope to verify those levels are indeed accurate. You can do the math and theory to select component values, but tolerances may affect the overall outcome. __________________ Don't make me reach through this monitor to slap you a good one!