http://www.mpegla.com/m4v/m4v-faq.cfm

I don't know what post Chris was referring to, however I can
give you 2 suggestions:

1. (this may or may not work, it depends on whether the
codec's DLL uses shared resources or absolute memory
locations) for each instance of the codec you need, make a
temporary copy of the DLL with a different name then do
something like:

HDRVR hDriver
    = OpenDriver(L"codec_001",NULL,0L);
HMODULE hModule
    = GetDriverModuleHandle(hDriver);
DRIVERPROC fDiverProc
    = (DRIVERPROC)GetProcAddress(hModule,"DriverProc");
ICInstall(*(DWORD*)"VIDC",*(DWORD*)"MP42",
    (LPARAM)fDiverProc,NULL,ICINSTALL_FUNCTION);
HIC hCodec
    =
ICOpen(*(DWORD*)"VIDC",*(DWORD*)"MP42",ICMODE_COMPRESS);
...
ICClose(hCodec);
ICRemove(*(DWORD*)"VIDC",*(DWORD*)"MP42",0);
CloseDriver(hDriver,0,0);

or use ICOpenFunction() instead of ICInstall()+ICOpen() (in
which case, ICRemove() is not needed).

2. (this should always work unless the DLL uses global
shared resources) Create a simple exe that does a single
compression and run as many instances as you need with
CreateProcess(). If you are compressing files, put all the
required code in this exe and pass the necessary parameters
on the command line. If you are compressing streams, read
and write the data through a stream connection (stdio, pipe
or stream socket) or a message-based connection (datagram
socket): the server side of the connection should be opened
by the main application before running the helper exe and
the parameters required to open the client side can be
passed in the command line. In any case, the result/error
can be returned as the process' exit code. As a bonus, if
you use named pipes or sockets, you can even create a
distributed application (over a network, stream sockets are
better while locally datagram sockets are more efficent and
easier to use). Of course, whatever the IPC mechanism you
use, this is a lot slower than having multiple instances of
the codec in the same process.

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