
IBM39MPEGS42x
IBM39MPEGSI
MPEG S422, MPEG S420 and MPEG SI Encoders
Sseries_sds_071701.fm.
02
July 17, 2001
S422 Encoder Operations and Features
7 of 25
Note: Combinations listed as INVALID will cause the encoder to either automatically adjust conflicting parameters
to be consistent or hang after initialization.
The VBV buffer size may alternatively be specified by the user via command code X'0005' to Host Register X'3D'
Picture Format
The encoder supports combinations of progressive and interlaced video formats as specified in the Table entitled:
“Input/Output Formats,” on page 8.
Input Pixel Interface
The pixel data interface will accept raster scanned digital video data up to
– For NTSC, 720x512 pixels/frame at 30 frames per second
– For PAL, 720x608 pixels/frame at 25 frames per second
Data is accepted at the pixel interface at a nominal rate of 13.5 MHz for a 16 bit YCbCr format, and 27 MHz for 8 bit
CCIR 656 format. The encoder will accept pixel data down to 64x64 pixels/frame. The data can be in either 4:2:0 or
4:2:2 format.
Maximum Picture Resolution
The encoder can support various picture widths, for example 720, 704, 608, 544, 352 etc. The encoder retrieves
the first n number of pixels from each active input picture line, where n is specified by the user in Host Register
X’14’. The encoder will ignore the number of video lines specified by the user in Host Register X’1B’ and
subsequently processes the number of video lines specified by the user in Host Register X’15’.
4
:2:2 to 4:2:0 Chroma Conversion Operation
Input video data can be in either the 4:2:2 or 4:2:0 format. The encoded output format can also be 4:2:2 or 4:2:0.
Valid combinations of these formats in and out of the encoder are shown in Table entitled: “Input/Output Formats.”
When the video source format is 4:2:2 and the encoded output format is 4:2:0, a conversion from 4:2:2 to 4:2:0 will
need to be done. The encoder can internally perform the 4:2:2 to 4:2:0 conversion.
The encoder supports four chroma conversion modes. Host Register X’04’ bits 4-3 are used to select the chroma
conversion mode. The choices are: frame convert, field convert, drop field and output convert An on-chip 2 tap
filter is used in each conversion mode. The contents of Host Register X’04’ bits 4-3 remain effective until changed
by the user. This register may be changed on any input picture boundary, during input picture gaps. The encoder
allows this parameter to be dynamically changed while encoding is in progress. However, if a change to this
parameter is processed between fields of a given input frame, the result is unpredictable. There is no on-chip
Maximum Video Resolution
4:2:0
Luminance
4:2:0
Chrominance
4:2:2
Luminance
4:2:2
Chrominance
NTSC
60 fps (1)
720x256
360x128
720x256
360x256
NTSC
30 Fps (2)
720x512
360x256
720x512
360x512
PAL
50 fps (1)
720x304
360x152
720x304
360x304
PAL
25 Fps (2)
720x608
360x304
720x608
360x608
Note: (1) fps = fields per second (2) Fps = frames per second