
IBM39MPEGS42x
IBM39MPEGSI
MPEG S422, MPEG S420 and MPEG SI Encoders
S420 Encoder Operations/Features
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Sseries_sds_071701.fm.02
July 17, 2001
S420 Encoder Operations/Features
This section, contains operations and features specic to the S420 product. Please refer to Section 8.4, “Basic
Register Denitions”, of the MPEG-2 S-Series Encoder User Application Guide, for a detailed description of each
host register referenced.
MPEG-2 Support
The MPEG-2 standard denes several syntactic subsets at which compliant encoders and decoders may operate.
These subsets were dened to make the implementation of encoders and decoders more practical. Each subset is
dened in terms of a prole and a level. The prole designation represents the syntactic subset of the MPEG-2
standard supported by a given encoder or decoder implementation, and the level designation provides constraints
for various bitstream parameters.
The encoder conforms to the Main Prole at Main Level (MP@ML) plus extension specications provided in the
MPEG-2 standard. The extension includes up to 50Mb/s and 11 bit DC precision. In addition, the following syntactic
subsets of the MPEG-2 standard are supported by the encoder:
MP @ HL (Main Prole @ High Level)
SP@ML (Simple Prole at Main Level)
ISO/IEC 11172 (MPEG-1)
In addition, the encoder can operate beyond the MP@ML specications by supporting encoded bitrates of up to 50
Mbps and a DC precision of up to 11 bits. When operating beyond the MP@ML specications (i.e.up to 15 Mbps
and 8 to 10 bits DC precision), provisions are made to allow the user to dene encoder operations up to Main
Prole at High Level (MP@HL).
The user can choose the syntactic subset based upon the user-specied parameters in effect while encoding a
given sequence. For example, Host Register X’23’, bits 6 and 5, enable the user to select the output prole. Also,
the user can produce an MPEG-1 compliant bitstream by setting the user-specied parameters listed in Section
7.3.1, “Overview”, of the MPEG-2 S-Series Video Encoder User Application Guide.
When the selected bitrate is higher than 15 Mb/s or the selected DC precison is 11 bit, Main Prole and High Level
are placed in the output header. Otherwise, Main Prole and Main Level are used.
VBV Buffer Size
At chip power on and initialization, the VBV buffer size is set to a default value based on how the following
initialization parameters are set by the application:
MPEG Standard via Host Register X'00', bit 0
Prole Conguration via Host Register X'23', bits 6 and 5
Bitrate via Host Register X'01' and Host Register X'02', bits 13 to 12
DC Precision via Host Register X'28', bits 1 to 0
SIF Picture Resolution via Host Registers X'07', bits 6 and 1, X'0A', bits 11 to 0, X'15', bits 11 to 0, X'19', bit 0,
and command code X'000C' to Host Register X'3E'