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.

2.2MPEG 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.

2-2Sun MediaCenter Server Administrator’s Guide • December 1997

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Sun Microsystems 2.1 manual Mpeg Encoding Requirements for Trick Play