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How to make a Time Base Correct for Video?

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leonqin

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Time Base Correct for Video?
 

casual3_2002

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Re: How to make a TBC?

Timebase Corrector is actually a 'sync doctor' (from Video Demystified Glossary), most of the time when the video source is from VCR, sync pulses get screwed up and you should use some heuristics to correct them. There is no standard way to do that, it's up to you to design an ad-hoc TBC.

casual3
 

spktu

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Any FPGA TBC solutions for a CCIR656 stream?

Any FPGA TBC solutions for a CCIR656 stream?
 

nachin

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Re: How to make a TBC?

I have the same problem.

I would like to "clean" a 27 Mhz Clock signal from a CCIR656 stream.

Do you know any good noise solution to do that?

Nacho.
 

barrybear

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Re: How to make a TBC?

Timebase correctors are used to stabilise and correct the fluctuations in sync pulse signals when a video signal is distorted . The most common use is for video tape syncrinisation. Video signals tend to very duo to tape strech and deack mechanics. They are quite difficulte to build as I have tryed and My advice would be to look for a tried and tested circuit on the net.

Barrybear
 

spktu

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Can You recommend smth as "tried and tested" TBC ?

Can You recommend smth as "tried and tested" TBC ?
 

spktu

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What kind of memories are used in TBC:

What kind of memories are used in TBC:
- only dual-ported
- or common SDRAM are also OK ?
 

shawndaking

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Re: How to make a TBC?

There Are 2 Diferent Problems with clocks:

1. JITTER

2. TBC.

TBC Correction Can Solve JITTER Problems, However De-Jitter Circuit Can't Solve TBC Problems.

The Solution That Is Done Is Usually By Manipulating Video Fields Or Frames. VIDEO Buffering Is Always Needed (With SDRAM For Example).
 

pit

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Re: How to make a TBC?

Hi!

There are simple TBCs like that one used in Panasonic AG4700 and similar devices. This TBC corrects 3 consecutive transmitted lines so they are precisely in time. When the first line has left the memory the fourth line is stored into it so always 3 lines are corrected.

This helps reducing jitter which appears at the h-sync. It helps when the picture is basically in sync but the line beginnings are unstable.

If the pictures (frames) are not in sync to each other (from two asynchronous sources) you will have to use a full-frame TBC. This one stores a complete frame and is more difficult to build. For a simple 3-line TBC look at the schematic of the VTR mentioned above.


CU
 

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