Date: Sun, 28 Jan 1996 14:24:19 -0700 (MST) From: Terry Lambert <terry@lambert.org> To: jkh@time.cdrom.com (Jordan K. Hubbard) Cc: terry@lambert.org, luigi@labinfo.iet.unipi.it, james@miller.cs.uwm.edu, dufault@hda.com, hackers@freebsd.org, hasty@rah.star-gate.com, multimedia@rah.star-gate.com Subject: Re: Amancio's tv program with capture! Message-ID: <199601282124.OAA01493@phaeton.artisoft.com> In-Reply-To: <28161.822813031@time.cdrom.com> from "Jordan K. Hubbard" at Jan 27, 96 11:10:31 pm
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> > But that object can't be exported as a shared memory region of a type > > the server can understand, since the layout won't match that of the > > Xshm protocol. > > Maybe I really am missing the boat, but I'm still having a hard time > understanding that if (and forgive me if I resort to pseudo- code - > it's been a long week): > > fbmem = mmap(.. blah ..) > shmid = shmget(.. some memory chunk size and allocation info ..) > ximage->data = shmat(shmid, 0, 0); > bcopy(fbmem, ximage->data, ..size..) > > Works *just fine*, e.g. the ximage data is happy to point at the > memory allocated by shmget and I can bcopy straight into this region > from the frame buffer, sans any special offsets or conversion, then > how can: > > fbmem = mmap(.. blah ..) > shmid = shmget(.. no memory please, just an entry ..) > ximage->data = shmat(shmid, fbmem, 0); > > work when shmget() doesn't support any such semantics? It seems like > that would be the minimum level of hacking required to even give this > a ghost's chance of working. You can support those semantics for mmap using a pseudo device to actually establish "just an entry" given the normal mmap argument space. This is still a kludge because you still have two sets of memory that can't be reconciled: the physical memory on the video capture card, and the physical memory on the display card. You *can't* map them to the same location. Terry Lambert terry@lambert.org --- Any opinions in this posting are my own and not those of my present or previous employers.
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