•4:2:2 ‐ This format is used for high‐end video authoring
•4:2:0 ‐ The vast majority of delivery codecs use this format.
ÆThere is one chroma sample per 2 x 2 block of pixels. This chroma sample looks nearly as good as 4:4:4, but at half the bits per frame.
• 4:1:1‐ NTSC DV and PAL DVCPRO use this format.
ÆIt contains the same number of bits per frame as 4:2:0 but with one sample per
4x 1 block of pixels.
Æbetter for interlaced content because each field gets its own sample; however, it can result in visible chroma artifacts in areas of high saturation
• yUV‐9 ‐ This format has one chroma sample per 4 x 4 block of pixels.
Æresults in noticeably degraded quality, so it isn’t used in modern codecs.
Audio Compression
The most fundamental factor in audio is sampling rate, which is measured in Hertz (Hz), or cycles per second. Audio CDs use 44100 Hz, or 44.1 kilohertz (KHz), which provides excellent reproduction.
The table below shows the typical sample rates for common use.
SAMPLE | USED | SUFFICIENT FOR |
|
|
|
8 KHz | Phone system | Speech |
|
|
|
11 KHz | Old multimedia standard | Better Speech |
|
|
|
22.050 KHz | Old multimedia standard | Recognisable music |
|
|
|