To Deinterlace Video
[The feature associated with this page, Windows Media Format 11 SDK, is a legacy feature. It has been superseded by Source Reader and Sink Writer. Source Reader and Sink Writer have been optimized for Windows 10 and Windows 11. Microsoft strongly recommends that new code use Source Reader and Sink Writer instead of Windows Media Format 11 SDK, when possible. Microsoft suggests that existing code that uses the legacy APIs be rewritten to use the new APIs if possible.]
Some sources of video, such as video capture cards, deliver video data for interlaced display. Each frame of interlaced video is made up of two fields. The top field contains the first line of video and every other line thereafter. The bottom field contains the second line of video and every other line thereafter. So one field contains all of the even numbered lines and the other contains all of the odd numbered lines. The fields that make up a frame represent slightly different presentation times so that, when interleaved, they do not form a static image.
When you want to display video on a computer monitor, each frame of the video should be displayed as one image (this method of displaying video one whole frame at a time is called progressive video.) If you display interlaced video progressively, the frames may not look right, because of the time difference between the two fields. The Windows Media Video codec and the Windows Media Video Advanced Profile codec both support a preprocessing feature that converts interlaced content into progressive frames.
To have the codec deinterlace input video, call the IWMWriterAdvanced2::SetInputSetting method. The setting to use is g_wszDeinterlaceMode. Set the deinterlacing mode to one of the following values.
| Value | Description |
|---|---|
| WM_DM_NOTINTERLACED | Input is progressive. Use this setting to stop deinterlacing when you have previously set the deinterlacing mode to another value. |
| WM_DM_DEINTERLACE_NORMAL | Select this mode to blend the even and odd fields of an interlaced frame (using a motion compensation mechanism).Benefits:
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| WM_DM_DEINTERLACE_HALFSIZE | Select this mode when the output resolution is half, or less, of the input resolution. For example, use this mode when the input video resolution is 640 x 480 pixels and the output video resolution is 320 x 240 pixels.Benefits:
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| WM_DM_DEINTERLACE_HALFSIZEDOUBLERATE | Select this mode when the output resolution is half, or less, of the input resolution and the output frame rate is twice as high. For example, use this mode when the input video resolution is 640 x 480 pixels at 30 interlaced frames/sec and the output video resolution is 320 x 240 pixels at 60 frames/sec.Benefits:
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| WM_DM_DEINTERLACE_INVERSETELECINE | Select this mode to convert telecined 30 frames/sec video into the 24 frames/sec of the original film.Benefits:
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| WM_DM_DEINTERLACE_VERTICALHALFSIZEDOUBLERATE | Select this mode when the vertical output resolution is half, or less, of the input vertical resolution and the output frame rate is twice as high. For example, the input vertical video resolution is 640 x 480 pixels at 30 interlaced frames/sec and the output vertical video resolution is 320 x 240 pixels at 60 frames/sec.Benefits:
|
For mixed content, set the deinterlacing mode as needed before passing samples of a new type. For example, to start encoding with progressive input, you don't need to set any deinterlacing mode. If some samples then require normal deinterlacing, you must set the deinterlacing mode to WM_DM_DEINTERLACE_NORMAL. To then process additional progressive samples you must set the deinterlacing mode to WM_DM_NOTINTERLACED.
Inverse Telecine Settings
For a description of inverse telecine, see To Use Inverse Telecine.
If you set the deinterlacing mode to WM_DM_DEINTERLACE_INVERSETELECINE, you can specify the telecine pattern of the first input frame by calling the IWMWriterAdvanced2::SetInputSetting. The setting to use is g_wszInitialPatternForInverseTelecine. Set the initial pattern to one of the following values.
| Value | Description |
|---|---|
| WM_DM_IT_DISABLE_COHERENT_MODE | Specifies that the input media has gone through the telecine process but that the frames are no longer in a predictable pattern. This usually indicates that the media was edited after the telecine processing. When you use this setting, the codec attempts to reconstruct the original frames on its own. |
| WM_DM_IT_FIRST_FRAME_IN_CLIP_IS_AA_TOP | Specifies that the top field of the AA frame is the first sample. |
| WM_DM_IT_FIRST_FRAME_IN_CLIP_IS_BB_TOP | Specifies that the top field of the BB frame is the first sample. |
| WM_DM_IT_FIRST_FRAME_IN_CLIP_IS_BC_TOP | Specifies that the top field of the BC frame is the first sample. |
| WM_DM_IT_FIRST_FRAME_IN_CLIP_IS_CD_TOP | Specifies that the top field of the CD frame is the first sample. |
| WM_DM_IT_FIRST_FRAME_IN_CLIP_IS_DD_TOP | Specifies that the top field of the DD frame is the first sample. |
| WM_DM_IT_FIRST_FRAME_IN_CLIP_IS_AA_BOTTOM | Specifies that the bottom field of the AA frame is the first sample. |
| WM_DM_IT_FIRST_FRAME_IN_CLIP_IS_BB_BOTTOM | Specifies that the bottom field of the BB frame is the first sample. |
| WM_DM_IT_FIRST_FRAME_IN_CLIP_IS_BC_BOTTOM | Specifies that the bottom field of the BC frame is the first sample. |
| WM_DM_IT_FIRST_FRAME_IN_CLIP_IS_CD_BOTTOM | Specifies that the bottom field of the CD frame is the first sample. |
| WM_DM_IT_FIRST_FRAME_IN_CLIP_IS_DD_BOTTOM | Specifies that the bottom field of the DD frame is the first sample. |
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