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DC120 Frames Per Second and Time Code

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by

Mike Mitchell

on 15 October 2014

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Transcript of DC120 Frames Per Second and Time Code

• In order to take up less bandwidth, television signals were sent in fields.

• Each field contains half of the horizontal lines that comprise a video image – one field contains all the even lines and one field contains all the odd lines.

• We refer to this as interlaced video.
Time Code
• Television originally needed a
stable time reference.

• It had a convenient one with
the carrier frequency of electrical
current coming out of the
AC outlet – 60Hz.
Time Code

NTSC
- National Television System Committee
- They come up with the standards that
American broadcasters must adhere to.


SMPTE
- Society of Motion Picture and
Television Engineers
-
also the name given to time code.
Time Code
Frames Per Second and Time Code
• A system of drop-frame time code was adopted.

• It’s important to remember that no actual frames are
ever dropped – just the time code numbers.

• Drop-frame time code: To keep the time code and
wall clock in perfect synch, 2 time code frames are
dropped every minute except the 10th minute
(minutes: 00, 10, 20, 30, 40, 50).
Time Code
• One of the results was that the frame rate was slowed
down by .1% which meant that the new frame rate was
29.97.

• Because this new system slowed down frame rate,
it would no longer correlate to the actual clock on the
wall after a minute or so. An extra 18 frames are
accumulated per 10 minutes.
Time Code
• With the advent of color television, engineers found a
way to keep the B&W transmission system intact.

• This meant that consumers were not forced to buy
new TV’s. The color information was sent along with
the old B&W signal.
Time Code
• These fields clocked to each cycle of the carrier
frequency.
– 60 cycles per second = 60 fields.
– 60 fields, in turn, equal 30 frames per second.


• Because the carrier frequency in Europe is 50Hz,
they have a frame rate of 25fps. (EBU – European
Broadcasting Union)
Time Code
• It wasn’t until the advent of sound-on-film systems
in the late 1920’s that frame rate standardization was
required.

• Playback pitch had to match that of the originals
recording.

• 24fps became the standard because it was fast enough
to do away with some of the “flicker” issues of lower
frame rates.
FPS
FPS
• Frames per second

• A frame is essentially an individual
picture.

If you put enough pictures together, fast enough, you get the appearance of motion.
Zoetrope
One of the earliest forms of animated movement was the Zoetrope.
Pixar Zoetrope
Full transcript