[Qt-interest] [OT] RE: video codecs

[Mehmet Kaplan]

"What do you mean by THE codec? There is no such thing as THE codec on a
system."I don't mean a static codec. i mean all the codecs currently
installed on the system.

my purpose is clearly like this:
i want to process video files frame by frame.
for video processing i can find algorithms and libraries, there isn't any
problem here.
for video processing, also i want to give a large container (mpeg, avi) and
codec support.
the first approach is to add encoder and decoder codes (c,c++ etc) of every
codec to my program.
second approach can be use a library, class, framework, namespace like
phonon that detects the codecs installed on the system. i can use phonon
namespace of Qt for playing video files (codec of this video is installed on
the system).
but phonon does not give the support for grabbing frames from these video
files. but for video processing i need all frames of a video.

as an example when user tries to process a video file with xvid codec, my
program won't let it. but after the user installed xvid codec to his/her
system, without any change on my program i want to process any video file
with xvid codec.

On Fri, Jun 12, 2009 at 3:03 PM, <Oliver.Knoll at comit.ch> wrote:

> Mehmet Kaplan wrote on Friday, June 12, 2009 11:21 AM:
>
> > as i read ffmpeg gives a huge codec support and this support is
> > growing. but it can't automatically detect the codec installed on the
> > system.
> > basicly really i want is a phonon like system  which detects the
> > codec installed, plus gives frame data for further process (not
> > available in phonon), also.
>
> What do you mean by THE codec? There is no such thing as THE codec on a
> system. Usually there are SEVERAL codecs available, such as MJPEG, h.264,
> MPEG 2 etc., and usually they are somehow "known" to the media system, for
> example as DirectShow filters. So when you try to play a given media stream
> the applicable codecs are detected and used for decoding that stream.
> Likewise if you want to ENCODE data you have to specify WHICH of the
> (possibly many) codecs you want to choose.
>
> And AFAIK this is exactly what ffmpeg does: it provides you a bunch of
> codecs, and possibly even can make use of the codecs which are installed on
> the system and are available as DirectShow filters (not sure about that
> though, read the ffmpeg docs).
>
> So if you mean by "[ffmpeg] can't automatically detect the codec installed
> on the system" that "ffmpeg can't use already installed codecs (which are
> available as DirectShow filters)", and the ffmpeg docs state explicitly
> that, then yes, you would need another solution, probably a solution
> directly based on DirectShow (read: platform dependent).
>
> On the other hand, what is the use case that you explicitly want to use
> "exactly this codec which is installed on the system"? Typically a use-case
> scenario for me would be "I want to encode the data as h.264 in a
> platform-independent way", and if ffmpeg provides such a codec (whether it
> brings its own plugins or makes use of existing DirectShow ones I don't
> care) then I would be happy.
>
> But maybe I don't understand your actual question?
>
> Oh, and by the way, I just found this one:
> http://ffmpeg.org/faq.html#SEC29 - "If you have built FFmpeg with
> ./configure --enable-avisynth (only possible on MinGW/Cygwin platforms),
> then you may use any file that DirectShow can read as input."
>
>
> Cheers, Oliver
> --
> Oliver Knoll
> Dipl. Informatik-Ing. ETH
> COMIT AG - ++41 79 520 95 22
> _______________________________________________
> Qt-interest mailing list
> Qt-interest at trolltech.com
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>
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