Reading Streams with Non-Square Pixels
[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 It has been superseded by Source Reader and Sink Writer.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.]
Reader applications that need to correctly handle non-square pixels should examine both the stream-level attributes in the ASF header and the data unit extensions on each sample. There are two cases when the output rectangle must be adjusted to compensate for non-square pixels.
When the source content has been captured from a device such as a DV (digital video) camera with non-square pixels in its CCD, a reader application must adjust its video output rectangle so that the image displays correctly on a computer monitor with square pixels.
When your reader application outputs video that will be played back on an NTSC television, for example through an S-Video out connection on the video card, you must adjust the video rectangle so that the image displays correctly on the television's non-square pixels.
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