EN8 – H.264 8CH HD Encoder / Manual
#B. GOP Structure
- Frame Type
- What is GOP (Group of Picture)
Assemblage of a Key Frame (I-Frame) to next key frame.
ex) GOP Structure : I B B P, GOP size = 15
I B B P B B P B B P B B P B B P I… Frames are repeated in this form.
Generally, when GOP size increased resulted in increase of B-Frame. Consequently, image quality
deteriorated but the size/capacity can be reduced. On the other hand, if GOP size reduced then
B-Frame reduced and resulted in improvement on quality of image but the capacity(file size)
increases. However, if the transmission bandwidth is small, reducing the GOP size may
deteriorate the picture quality.
#C. Audio Codec and Rate
I-Frame
- Construction of a single complete image without using prediction.
- The best quality picture, but the largest capacity (file size).
P-Frame
- Use Forward Prediction.
- Contains the data of the part where the change occurred in previous I-
frame or P-frame.
-if referred I-Frame or P-Frame data is lost then this P-frame data is lost
too.
- The image quality is lower than [I-Frame]but capacity is smaller than I-
Frame.
B-Frame
- Use bidirectional prediction.
- Referred previous I-Frame and subsequent P-Frame or previous P-
Frame and subsequent P-Frame.
- Loss together with referred Frame data.
- The most degraded image quality but the smallest capacity.
MPEG-1 Audio Layer2
64, 96, 112, 128,b160, 192, 224, 256, 320, 384 (Kbps)
Default value : 128 Kbps
MPEG-2 AAC / MPEG-4
AAC
48~512(kbps)
Default value: 128 Kbps
