★ PROGRAMMER'S GUIDE ★ CD builder script grammar supplementary explanation
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CD Builder Script Grammar Supplementary Explanation

4. Precautions when building MPEG stream

Please note the following when building an MPEG stream.

● Sector rate specification
When building an MPEG stream with a CD builder, dummy data (empty sectors) will be included by the difference between the sector rate and the bit rate. As a result, the following problems occur:

  1. The file size becomes large.
  2. The look-ahead effect on the CD buffer is lost.

To remove empty sectors, specify as low a sector rate as possible, as long as the following relationships are met: That is, the sector rate value that exceeds the sum of all bit rates and is closest to it.

Sector rate ≥ total of all bit rates

To calculate the sector rate, see "Relationship between sector rate and bit rate" in the previous chapter.
If you specify 0 or 65535 for the sector rate, the sector rate that minimizes the dummy sector is automatically calculated and set.

● Channel interleaving of MPEG and multi-DOS files
For channel interleaving of MPEG files and multi-DOS files, once the MPEG video stream and MPEG audio stream are multiplexed to build the ISO11172 stream, the ISO11172 stream is used as the source file and channel interleaving with the multi-DOS file is performed again, so-called. This can be achieved by the 2-pass method.

[Execution procedure]

  1. Create Script 1 that multiplexes the MPEG video stream and the MPEG audio stream and outputs the ISO11172 stream as a DOS file.

  2. Run the CD builder using script 1.

  3. Create Script 2 to channel interleave the created ISO11172 stream and multi-DOS file.

  4. Run the CD builder using script 2.

● Definition of MPEG video stream
When defining an MPEG video stream using the FileSource command, write the file source type as MPEG_VIDEO.
This description identifies the file source as an MPEG video stream and appends 16 words of "0" data immediately after the sequence_end_code recorded at the end of the MPEG video stream.
This description is necessary for normal playback of the MPEG video stream in Sega Saturn.

Also, when defining an MPEG video stream using the MpegStream command, the same processing is performed by identifying the parameter VIDEO.

● ISO11172 stream subheader
When building an ISO11172 stream by multiplexing an MPEG video stream and an MPEG audio stream, the subheader is set to a value specific to the ISO11172 stream.

(a) Coding information
-7FH is set for the audio stream and 0FH is set for the video stream.

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★ PROGRAMMER'S GUIDE ★ CD builder script grammar supplementary explanation
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