[gst-devel] framerate and deinterlace2

[Brian Crowell]

2008/12/6 Julien Isorce <julien.isorce at gmail.com>:
> So a video source at 1080i uses as much bandwith as a video source at 1080p.
> I believed there was black lines in one interlaced frame and so 1080i was
> used for lower bandwith.

A video source running at 1080i @ 30 frames per second (that is, 60
fields per second) uses exactly half the bandwidth as 1080p @ 60
frames per second.

To the end viewer, they appear equally fluid, because they both
*appear* to be running at 60 frames per second. The non-interlaced
format will provide twice the vertical detail but will use twice the
bandwidth.

There are no blank lines when interlaced video is transmitted
digitally. Two adjacent fields in a 1080i picture, each measuring
1920x540 pixels, are combined to form a single frame measuring
1920x1080 pixels, where the even-numbered horizontal lines form one
field and the odd-numbered horizontal lines form another. The same
concept applies to standard-definition 480i video.


> So I do not understand why 1080i still exist because interlacing was
> iniatilly used for CRT tv to avoid flickering.
> So what are the reasons to use interlace mode in a full numeric chain ?
> (source, transport, visual)

I think it had to do with the fact that many early HDTVs were
CRT-based. Bandwidth requirements may have come into it.


> What's the most usual deinterlacing method used in FULL HD screens ?

Probably line doubling.

--Brian