Week 9 Flashcards
What is Video?
A sequence of still images (photographs) that create the illusion of movement when played in succession.
Question: What is each still image called?
Frame
How many fps is required for: Movies on film
TV
Computer Displayed Video
Movies on film = 24-30 fps
TV was originally= 29.97 fps (59.94
fields per second)
Computer Displayed Video =AT LEAST12-15 fps
Humans can distinguish as single images at how many frames per second?
At less than 10 fps
What is Digital Video ?
Each frame is a bitmapped graphic, stored as 0s and 1s
How is sampling of motion done?
Since each frame is just an image =
Each frame is sampled into a discrete samples and each sample becomes a pixel = Sampling process
What do we need to remember about number of samples and quality?
More samples means better quality (10 pixels by 10 pixels vs 200 pixels by 200 pixels)
More samples mean bigger file sizes (10 pixels by 10 pixels vs 200 pixels by 200 pixels)
How is quantizing of motion done?
Each pixel gets assigned a colour, maybe just 2 colours(black and white=1bit colour) or maybe 16 million colour (24 bit colour) =Quantization process
What else can we “sample” with MOTION?
- Timing of the motion
- Sampling = frames
- Higher FPS = more accurate motion, but larger file size
For still images RGB is commonly used, what is the model used for video?
YUV (YIQ) or YCbCr (for MPEG compression)
What is YUV (YIQ) or YCbCr (for MPEG compression)
Y = luminance (brightness)
UV = (CbCr) chrominance (color/hue)
Black and White TV only used the ____ signal (fill in the blank with Y, U, or V)?
Y
Which one will the human eye detect changes in more easily? How does this help us with compression? Where have we seen this used before?
Y (brightness), have seen this with images
