[Mp4-tech] about MPEG2 stream T-SDT

[Song]

Dear experts, 
I am trying to find the relationship between PCR, DTS and vbv_delay. 
I can find the following description at the section 2.4.2.3 of ISO13818-1. This is about T-SDT.
When the vbv_delay method is used, the final byte of the video picture start code for picture j is transferred from MBn to
the EBn at the time tdn(j) ¨C vbv_delay(j), where tdn(j) is the decoding time of picture j, as defined above, and
vbv_delay(j) is the delay time, in seconds, indicated by the vbv_delay field of picture j.
Can I reach a conclusion that the PCR at the start code of picture data equate to DTS - vbv_delay?
I checked a lot of MPEG2 streams to verify this, but vbv_delay always are too large. Can anyone explain me about the relationship?
Picture      PCR(ms)    DTS(ms)      VBV_delay(ms)         
1            0.796      373.122      577.244
2            20.7       406.489      562
3            86         473          575.389
Best Regards.
Bill Song
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