theora dev - Dec 2008 - DirectShow Theora Issue with RGB24

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.
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> this results in the video file being
> mirrored vertically.
This wouldn't be caused by using YUV colorspace instead of RGB,
but because the Theora code stores lines in the 'reverse' order
(eg, a negative stride). If you can control the order in which lines
are processed, just reverse this order. If not, a post processing
step that flips the image should be enough, and fast.

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.
Hi,

I've implemented a check to verify the bottom-up conforming with this page
http://msdn.microsoft.com/en-us/library/ms787796(VS.85).aspx

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
problems!

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,
Cristian.

Thanks a lot for the quick replies.

I have tried using RGB32 but unfortunatly I still get the same issue.  I
have tried a few other formats including RGB555 and they all work ok.

I shall flip the image for now.

Cristian - do you know if there are any timescales around implementing the
new function to check if the image needs flipping (not being pushy).

Cheers,
Steve.
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