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2-2 Sun MediaCenter Server Administrator’s Guide • December 1997
■ The timing information embedded in an MPEG file must exactly reflect the
constant bit rate encoded in the file. Specifically, the time differences between any
two consecutive PCR (SCR for Program Streams or MPEG-1 System Streams) time
stamps must exactly reflect the time required to play out the number of bytes
between the two PCRs (SCRs for Program Streams or MPEG-1 System Streams) at
the bit stream’s specified bit rate.
■ The bit stream must be encoded at constant bit rate, between 1.5 and 15 Mbit/sec.
You can encode a bit stream at any rate within this range.
■ Each bit stream must contain one and only one Program Association Table (PAT),
but these can be repeated as often as required. Multiple programs in one transport
stream is not supported.
■ Each bit stream must contain one and only one video stream.
■ For MPEG-2 Transport Streams, each MPEG-2 transport packet that contains the
Program Clock Reference (PCR) must occur in an even-numbered transport
packet, where the first transport packet in the stream is defined to be numbered 1,
and is odd. This is necessary to meet the ATM Forum MPEG-over-AAL5
requirement that, in the case where there are two MPEG-2 transport packets per
AAL5 packet, the PCR must be in the last transport packet in the AAL5 packet.
2.2 MPEG Encoding Requirements for Trick
Play
Trick play refers to the manipulation of video bit streams to create the effect of fast
forward and rewind, as found in conventional VCRs. To perform trick play, the Sun
MediaCenter server does not dynamically manipulate data within the normal-play
bit stream. Instead, the server switches from a normal-play stream to the appropriate
position in another bit stream that has the requested play speed and/or direction.
To enable trick play on the Sun MediaCenter server, you must provide a set of
distinct MPEG bit streams, beyond the bit stream that represents the movie at the
normal playback speed. These additional bit streams represent the content at several
speeds, in either the forward or reverse direction. If a content package does not
contain at least one additional bit stream beyond the bit stream for normal playback,
trick play functions are disabled.
All trick files must meet the following requirements:
■ All trick files must contain the identical video and audio PIDs as those of the file
at normal play speed.
■ All trick files must be encoded in a format (that is, MPEGTS, MPEGPS, or
MPEG1SYS) identical to the bit stream at normal play speed.