Is this VCD mux rate right?

Hi,

I have noticed that all compression programs write in mpeg header of VCDs that the mux rate is 176,400Bps... Why is that? I mean: 2324*75=174,300Bps

For SVCDs however, they use 348,600, which is correct because: 2324*150=348,600.

I'm tring to figure this out but can't... Anyone who understand this?

[groyal]

I think I understand how, though I'm not sure I understand why.

VCD and SVCD sectors, while both CD-ROM XA mode 2 form 2, apparently conform to different layouts yielding different payload sizes:

SVCD: 2352 (Sector Size)
       -12 (Sync)
        -4 (Header)
        -8 (Subheader)
        -4 (Error Detection Code)
      ====
      2324 (Payload Size)

thus 2324*150=348600,

whereas

 VCD: 2352 (Sector Size)
       -0 
     ==== 
     2352 (Payload Size)

thus 2352*75=176400.

Now, the VCDImager manual lists the program's sector output size at 2336 bytes, which would indicate a sector layout looking something like this:

[S]VCD: 2352 (Sector Size)
         -12 (Sync, i.e. sector start address information)
          -4 (Error Detection Code)
        ====
        2336 (Payload Size)

The upshot of this is that the mux rates for VCDImager (and minus multiplexing overhead, the maximum encoding bitrate) is apparently somewhat lower for VCD and slightly higher for SVCD than the encoder anticipates.

Well, the numbers you give are correct for SVCD but for VCD.... They both use the 2324byte sectors which is the standard Mode 2 form 2... (2336 is for 90min CD or 99min CD, can't remember exactly...)

I'm building aprogram that gives information about MPEG files so I suddenly noticed this odd fact... Maybe this is what I read about some DVD players only accepting VCDs muxed with the Philips toolkit? Maybe the Philips toolkit muxs the streams with 174,300 instead of 176,400? I really have to check it out...