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Video CODEC Description:

The video encoder implemented requires a YUV 4:2:0 non-interlaced video input and, therefore, pre-processing of the video input may be required depending on the application. For the video decoder, post-processing is needed to convert the decoded YUV 4:2:0 data to RGB format for displaying.


7.2.1    Features


  • Pre-processing:

− YUV 4:2:2 interlaced (from camera for example) to YUV 4:2:0 non-interlaced, only decimation and no filtering of the UV components

  • Post-processing:

− YUV 4:2:0 to RGB conversion

− Display formats of 16 bits or 12 bits RGB

− 0 to 90 degrees rotation for landscape and portrait displays

MPEG-4 Simple Profile Level 0, Level 1 and Level 2 support

H.263 and MPEG-4 decoder and encoder compliant

MPEG-4 video decoder options are:

− AC/DC prediction

− Reversible Variable Length Coding (RVLC)

− Resynchronization Marker (RM)

− Data Partitioning (DP)

− Error concealment, proprietary techniques

− 4 Motion Vectors per Macroblock (4MV)

− Unrestricted Motion Compensation

− Decode VOS layers


  • MPEG-4 video encoder options are:

− Reversible Variable Length Coding (RVLC)

− Resynchronization Marker (RM)

− Data Partitioning (DP)

− 4 Motion Vectors per Macroblock (4MV)

− Header Extension Codes

− Bit rate target change during encoding

− Coding frame rate change during encoding

− Insertion or not of Visual Object Sequence start code

  • Insertion of I-frame during the encoding of a sequence support

Encoder Adaptive Intra Refresh (AIR) support

  • Multi-codec support, multiple codecs running from the same code


 Video Architecture


Pixel Representation


Red, Green and Blue or RGB are the primary colors for the computer display and the color

depth is programmable up to 16 bits per pixel, RGB565 (5 bits for Red, 6 bits for Green and 5 bits for Blue).

In consumer video products such as DVD, digital camera, digital TV and others, the common color coding scheme is YCbCr where Y is the luminance, Cb is the blue chrominance and Cr is the red chrominance. Human eyes are much more sensitive to the Y component of the video and this enables video sub-sampling to reduce the chrominance component without being detected by the human eyes. This method is referred to as YCbCr 4:2:0, YCbCr 4:2:2 or YCbCr 4:4:4.

Figure 1 shows the sub-sampling techniques applied to the video.

Post-processing is needed to calculate the RGB values equivalent of the YCbCr data. The post-processing engine computes the following equations to obtain the gamma-corrected RGB information.

R = Y + 1.371(Cr 128)

G = Y 0.698(Cr 128) 0.336(Cb 128)

B = Y + 1.732(Cb 128)




. Figure7.2 : Chroma subsampling