Hope this is not redundant, otherwise smile about silly me.
Did you check the source of Multiple_MPEG2_Source.ax ?
(A file reader ax, in nimo codec pack for instance.) Its
officially source only on
http://fysx.acwu.com/Code/Code.html
and downloadable from Dooms Source page.
LIBRARY Multiple_MPEG2_Source.ax
DESCRIPTION 'I-Media Multiple MPEG2 Source Filter'
It should be able to show you what you asked for, or?