> > > My problem is that I need to store additional data per-sample. My
> > > first attempt was to use image description extensions to
> store them
> > > (one extension per-image-description) but I quickly noticed
> > that the
> > > image descriptions given in BeginBand() are always the same
> > (only the
> > > dataSize is changing). So I wrote and
> > IsImageDescriptionEquivalent()
> > > function for my codec which returns always false (since my
> > extension
> > > is always
> > > different) but then, there is one codec instance created for each
> > > frame!
>
> Search the list archive on this, there was a discussion on
> storing per-frame custom data sometime ago, with Tim Monroe
> replying with the way to do it I think. Let me know if you
> can't find it to search my mail archives...
I think the following discussion might help (I didn't remember well and
thought Tim had replied to it). See the mention to
AddImageDescriptionExtension and GetImageDescriptionExtension below. Please
follow up here with confirmation in case it did the job (always useful for
people searching list archives to know)
Cheers,
George
-----------------------
Hello Glenn,
Thanks a lot for your suggestion.
As a matter of fact, the format of the movie has already been changed so
that our component can be called appropriately. To do that, I wrote a tool
that converts the original movie (MPEG4 for example, and not necessarily a
.mov file per se) into a new QuickTime movie in which each frame is "typed"
as encoded with a proprietary codec, so I think there will be no objection
if the tool adds the metadata in an image description extension. I will
check that right now and modify my converter tool as needed if I'm allowed
to do that.
I'll let you know how it works.
Thanks again!
Olivier
At 01:33 am + 1300 16/03/2006, Glenn Anderson wrote
> At 11:48 am +0100 16/03/2006, Olivier wrote:
>> Hello,
>>
>> I have a movie that contains some metadata that are needed to
>> decode the frames. The proprietary metadata is unique but is
>> needed for each frame. This metadata is in the movie file, *not*
>> in the frames (it would not be efficient to repeat the same data
>> in each frame, of course).
>> I need to write a codec that decodes the movie frames, but I can't
>> see a way to access the movie file from the codec to read the
>> metadata. Is there any way to do that?
>> Or should I write a media handler instead to access the movie
>> metadata and from the media handler call the codec passing it the
>> metadata that it needs? Or should I write a data handler? Or a
>> combination of several components?
>
> Is it too late to change where the metadata has been put? If not,
> put it in an image description extension instead. That way only one
> copy of it will be stored in the movie, and it gets passed to your
> codec. See the AddImageDescriptionExtension and
> GetImageDescriptionExtension calls.
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