What is the difference between 608 and 708 closed captions?
608 are for analog NTSC TV and 708 are for Grand Alliance DTV, aka ATSC 1.0.
SMPTE Standards
How are captions carried in SMPTE 436M?
Carefully.
In what ways are CEA 708 closed captions backwards compatible with CEA 608 closed captions?
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What is the difference between how we insert closed captions for 720p video vs. 1080i video?
All captions are inserted into the video at the framerate of the video. and the frame rate for 1080i is 29.97 frames per second, where the frame rate for 720 captions is 59.94 frames per second.
In 1080i content, we insert captions in field 1 at 29.97 fps.
To get the same throughput when sending send 720p, the 720p data has to be half the amount of data of a 1080i payload since we’re sending it at every single 720p frame, and the frame rate is 59.94.
The 1080i framerate, 29.97 fps, means that 1080i is going to have twice as much data sent every time we send a Caption Data Packet (CDP).
Why do we need Simultaneous 608 and 708 Closed Caption Display?
When we’re looking at our SDI plant, we must verify that we have the full 608 caption payload and I have the full 708 caption payload.
What
Why is it harder to monitor 708 captions than it was for 608?
We must verify that the same exact services… are carried at the same time… in both 608 and 708. We must verify that the data is present, the data doesn’t have any errors in it, and which line the data is being inserted on.
Also in the VANC: Vchip rating, the TSID, the CGMS, and the broadcast flag. That’s all part of that XDS payload data that’s actually extracted out of the 608 service.
With 608 captions in analog TV, we put the ancillary data on a physical line that was part of the active video, line 21 field 1, so that it would get through our entire plant.
With DTV, we bury the 708 Caption Data Packet (CDP) within the SDI stream in the Vertical Blanking Information (VBI) in the VANC.
Why is line 9 the preferred line for 708 closed captions in DTV?
Why was HDMI developed?
HDMI was developed to reduce the number of cables between a output device and a monitor or tv set and for copyright protection when using digital devices.
Can HDMI carry closed caption data?
No. HDMI can’t carry caption data.The receiver must overlay the captions on top of the video and present it as burned-in or embedded captions to the receiving device.
In HD-SDI, the captions are carried as data packets in the vertical ancillary data space. 608 is buried inside of the 708 packets. With 708 captions, 608 is carried in the user data in the header of each picture start code.
HDMI won’t pass ATSC 3.0 context. How does Verance get the context beyond the HDMI cable?
The Verance watermark contains a URL and a timestamp that restores ATSC 3.0 context past the watermark.
Why does increasing light make it easier to read?
Why does increasing light make it easier to read?
It’s not because you’re increasing light. It’s because you are increasing contrast.
What is the Lechner Distance for a 65 inch TV?
9 feet.
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