source filter dynamic format change

Question

I have a direct show source filter that exposes 4 formats. All of them differs by size : 320x240 ... 640x480 all 24 bps. I need to support the following scenario:

* filter is connected using 640x480 format, graph is started and I need to change to 320x240 format.

 

From what I read regarding dynamic format change I need to do the followings:

* call IPinConnection.DynamicQueryAccept (or IPin.QueryAccept if IPinConnection is not available) with new media type

* if S_OK is returned I need to attach the new media type to the next sample I send.

* if an error is returned I need to force reconnection. I'm doing that using EC_DISPLAY_CHANGED event

 

My implementation:

 

I override DoProcessingLoop() as follows:

- if format change needed

   - create new media type

   - call DynamicQueryAccept or QueryAccept with new media type on connected pin

   - if format not accepted call filter->NotifyEvent(EC_DISPLAY_CHANGED, (LONG_PTR)connectedPin, 0);

- call GetDeliveryBuffer()

- call FillBuffer()

- if new format accepted

    - call pMediaSample->SetMediaType() with new media type

    - if S_OK is retuned change m_mt to new media type

- call Deliver() to deliver media sample

 

Also it says that in order for this to work negotiated buffer must not change. To support this, on DecideBufferSize() i provide a big enough buffer that will fit the biggest format that I can support.

 

VIDEOINFOHEADER:

Here I tried more versions:

 

1. for every media type I provided it's own VIDEOINFOHEADER:

    320x240 - rcSource= [0, 0, 320, 240] bmiHeader.biWidth= 320  bmiHeader.biHeigh= 240

   ............

    640x480 - rcSource= [0, 0, 640, 480] bmiHeader.biWidth= 640  bmiHeader.biHeigh= 480

 

2. all media types have the same biWidth and biHeight:

    320x240 - rcSource= [0, 0, 320, 240] bmiHeader.biWidth= 640  bmiHeader.biHeigh= 480

   ............

    640x480 - rcSource= [0, 0, 640, 480] bmiHeader.biWidth= 640  bmiHeader.biHeigh= 480

 

I tested with: Skype, AmCap, U-stream

 

My problems are:

with AmCap:

  - using first approach for VIDEOINFOHEADER media type is accepted, but the sample size is rendered using the media type negotiated on filter connection. Calling filter->NotifyEvent(EC_DISPLAY_CHANGED, (LONG_PTR)connectedPin, 0) will force a reconnection and the problem is solved

  - using second approach for VIDEOINFOHEADER I have two problems:

    * necociated media type is always 640x480

    * any new media type is not accepted and filter->NotifyEvent(EC_DISPLAY_CHANGED, (LONG_PTR)connectedPin, 0) will not work, because of fixed negociated media type.

 

with Skype:

- using first approach for VIDEOINFOHEADER media type is accepted, but the sample size is rendered using the media type negotiated on filter connection. Calling filter->NotifyEvent(EC_DISPLAY_CHANGED, (LONG_PTR)connectedPin, 0) will force a reconnection, the new negotiated type is the right one, but skype will still use the old one.

- with second approach skype will always use BITMAPINFOHEADER biWidth and biHeight to render the sample

 

with u-stream:

 - using first approach we have the same behaviour as skype

 - using second approach we have same behaviour as AmCap.

 

I tried working with rcTarget, but seams to be ignored by all three.

 

I need to have consistent behaviors on all three application. What is wrong with my approach?

 

Iulian

Answer 1

I need to have consistent behaviors on all three application. What is wrong with my approach?

Nothing. The applications are simply badly written and do not support a dynamic format change (which are not really required to) or rcSource (which they should).

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MVP :: DirectShow / MediaFoundation <http://www.riseoftheants.com/mmx/faq.htm>