[Ffmpeg-devel] Re: directshow grab device?

Compn tempn
Fri Apr 20 23:08:35 CEST 2007

On Fri, 20 Apr 2007 15:58:50 -0500, Aaron Griffin scribed:

>On 4/20/07, Ramiro Ribeiro Polla <ramiro at lisha.ufsc.br> wrote:
>> Hello,
>> Aaron Griffin wrote:
>> > Hey all,
>> > I've looked through the archives, though not exhaustively, but I
>> > can't seem to find a windows based grab device for libavformat
>> > besides drffmpeg.
>> >
>> > I'm curious if anyone has actually done work on this, and if the
>> > ffmpeg people would be interested in this.  The reason being that
>> > I am currently writing a (commercial) app which does just this,
>> > and I was debating doing the reverse of ffdshow - that is, convert
>> > directshow style to ffmpeg, and not ffmpeg style to directshow.
>> >
>> > Has anyone done any work in this regard and/or would be interested
>> > in it if I were to throw something together?
>> >
>> I did VFW capture, and sent an unfinished patch to the mailinglist
>> earlier on this year (probably january or february).
>> I gave up on it, but it's being used somewhere in bbc.co.uk. I don't
>> have the final version anymore, it's somewhere on my older shut down
>> computer. I'd have to bring it back up...
>Yeah, but the biggest hurdle here is that VFW dies with Vista.  In
>most of my tests, VFW seems to actually be more performant for
>grabbing raw frames.  *sigh*
>> If you can really convert directshow style to ffmpeg, that would be
>> nice. It will be hard though, since directshow style is quite ugly
>> for ffmpeg's standards. Also, remember that the code must compile on
>> MinGW, not MSVC++. When I tried that with MinGW, I had to change a
>> bunch of stuff in dshow.h.
>Actually, the plan was to use wine's DirectShow headers, as they
>nicely wrap COM into C style, so it doesn't force C++ usage, which
>would be bad news in ffmpeg.
>I'm still trying to figure out which is actually better - the
>less-code ISampleGrabber route (simply sticking an ISampleGrabber in
>between the device filter and a NullRenderer filter), or the more
>complex custom filter version, which requires implementing 5-6
>interfaces in each of 4 distinct classes.  As it stands I see very
>little difference in performance, but apps like VLC go the custom
>filter route.  Would anyone happen to know why this is, I can't seem
>to find any information besides some speculation that ISampleGrabber
>doesn't work on Windows 2000, though that doesn't seem right.

maybe you should look at mplayer's dshow tv:// patch

might give you some insight..


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