[theora-dev] DirectShow Theora Issue with RGB24

Cristian Adam cristian.adam at gmail.com
Thu Dec 11 00:47:06 PST 2008

Steve Scott wrote:
> Hi,
> I hope you can help, I am in need of some assistance with the 
> DirectShow filters for Theora. 
> I have successfully created a working capture graph using OGG / Vorbis 
> / Theora, however, when I add a Sample Grabber Directshow filter 
> between the FFDShow decoder and Theora Encoder, this results in 
> the video file being mirrored vertically.  I have noticed that the 
> original CaptureGraph was using YUV12, but the SampleGrabber is 
> configured to use RGB24.  Is it likely that this is the cause of the 
> problem? 
> Unfortuntatly I need to stick with RGB as I have already written a 
> significant amount of code around this.
> Should I not be using RGB24 as an input to the OGG Mux filter?
> If not, can anyone suggest a good (free) Colour Space Convertor to 
> convert from RGB24 -> YUV12 (The Microsoft only seems to convert 
> between different RGB formats)
> Many thanks,
> Steve.

I've implemented a check to verify the bottom-up conforming with this page

I've tested it with RGB32, but somehow the RGB24 doesn't work correctly, 
biHeight is positive so the image
should be bottom-up, but it's not! I was thinking of removing the RGB24 
support because of this, its causing

My suggestion is to use RGB32.

In the future I will implement a function to specify if the image should 
be flipped or not.

Hope this helps,

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