Fusion 878A
2.0 Functional Description
PCI Video Decoder
2.10 Video Data Format Conversion
100600B
Conexant
2-27
2.10 Video Data Format Conversion
2.10.1 Pixel Data Path
The video decoder/scaler portion of the Fusion 878A generates a video data
stream in packed 4:2:2 YCrCb format. The video data is then color
space-converted and formatted in a 32-bit wide DWORD.
illustrates
the steps in converting the video data from packed 4:2:2 YCrCb to the desired
format. The YCrCb 4:2:2 data is up-sampled to 4:4:4 format prior to conversion
to RGB. It can then be dithered, have gamma correction removed, or be presented
directly to the byte swap circuit.
In the case where 4:1:1 data is desired, the 4:2:2 data is first down-sampled,
then packed into BtYUV format (see
) or converted to planar format and
vertically sub-sampled to achieve the YUV9 format. Alternatively, packed 4:2:2
data may be converted to planar 4:2:2 and vertically sub-sampled to YUV12
format. The vertical sub-sampling is achieved via the appropriate DMA
instructions (see
Fusion 878A also offers a Y8 color format, in which the chroma component of
the packed 4:2:2 data is stripped and the luma component is packed into 8 bits.
This format is otherwise known as gray scale.
lists the various color
formats supported by the Fusion 878A and the mapping of the bytes onto 32-bit
DWORDs.
2.10.2 Video Control Code Status Data
In addition to the pixel information, the Fusion 878A’s Video Data Format
Converter provides four bits of video control status code to the FIFO. These four
bits of status code STATUS[3:0] are based on inputs from the video
decoder/scaler block of the Fusion 878A and convey information about the pixel
data and the state of the video timing (see
). STATUS[3:0] bits have
four uses:
1.
To specify the FIFO mode (packed or planar)
2.
To provide information regarding the pixel data (respective position of the
pixel and number of valid bytes)
3.
To indicate whether the pixel data is valid
4.
To signal the end of a capture enabled field
Содержание Fusion 878A
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