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2004 Jan 26 27
Philips Semiconductors Product specification
MPEG-2 video and MPEG-audio/AC-3
audio encoder with multiplexer
SAA6752HS
7.7 Multiplexer
7.7.1 GENERAL
The system stream multiplexer combines compressed
audio and video streams into a single MPEG system
stream. Presentation data is synchronized by the use of
time stamps as specified in the MPEG systems standards.
The multiplexer ensures an MPEG-compliant multiplexing
with respect to buffer maintenance, synchronization and
data alignment. It takes care of the system specific
requirements for D-VHS, DVD, DVB and ATSC.
7.7.2 MULTIPLEXER CONFIGURATION OPTIONS
The following configuration options can be selected from
the host:
• STREAM FORMAT. Selection of audio or video
elementary stream, packetized elementary stream,
program stream or transport stream options and general
system parameters including maximum system bit rate,
number of flushing bytes and PES header IDs.
• TRANSPORT STREAM SYSTEM MODES. In TS
mode, it is possible to set packet IDs and download
system information tables.
7.7.3 MULTIPLEXER STATUS INFORMATION
The following status information can be selected from the
host:
• METABYTES INFORMATION. If selected and in
program stream or pack stream, it is possible to insert
video and audio status information into the stream
output as special metabyte data packets for later system
processing.
• NUMBER OF BYTES PER GOP. It is possible to read
the current system bit rate of the output stream.
7.7.4 ELEMENTARY STREAM OUTPUT
Video and audio elementary stream outputs can be
selected.
7.7.5 PACKETIZED ELEMENTARY STREAM OUTPUT
Packetized Elementary Stream (PES) outputs can be
selected. There are two options: PES (DVD) and PES
(TS). Variable bit rate is only available in PES (DVD) mode
and constant bit rate only available in PES (TS) mode.
The video and audio PES IDs can be programmed via the
I
2
C-bus. Original copy or copyright flags can also be set.
7.7.6 PROGRAM STREAM OUTPUT
Program stream output, intended for storage recording
applications, can be selected. Time slot reservation for
navigation packets is available. Metabytes can be
appended after each pack, see Section 7.7.10.
7.7.7 PACK STREAM OUTPUT
A special mode called pack stream can be selected. This
is a program stream but without the MPEG buffer model
implemented. This minimizes the throughput time of video
and audio data through the SAA6752HS and is intended
for applications where low latency is important. In this
mode no program stream header is inserted.
7.7.8 TRANSPORT STREAM OUTPUT
Transport stream output can be selected. The video, audio
and PCR (clock) Packet Identifiers (PIDs) can be
programmed. System information tables can be
transferred to the SAA6752HS via the I
2
C-bus. If transport
stream output is combined with DIO master mode as
output mode then packets are sent in a controlled way, so
that a set-top box can be connected.
7.7.8.1 Transport stream with variable bit rate
Optionally a transport stream without null packets, i.e. with
variable bit rate can be generated. Via subaddress C3H it
is possible to select constant or variable TS bit rate.
At constant TS bit rate mode null packets are delivered at
the multiplexer output to achieve the constant TS bit rate,
even if the video bit rate is variable.
At variable TS bit rate mode no Null Packets are inserted
at the multiplexer output. This mode can be used in
combination with variable video bit rate.
7.7.9 INSERTION OF LEADING NULL BYTES
For some applications it is helpful to deliver leading
flushing bytes before the stream content starts. Null bytes
(00H) will be inserted at the beginning of a stream, if
programmed by subaddress F6H. By default no null bytes
will be delivered.