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Working with Inputs

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[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 It has been superseded by Source Reader and Sink Writer.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.]

Just as the proper stream configuration in the profile is required to get the codec to compress a stream, you must also ensure that the type of uncompressed media you pass to the writer is accurately described. Every Windows Media codec has an associated default input type, but several input types are supported. You can examine the supported inputs and select the one that matches your data. The process of working with inputs is summarized in the following steps:

  1. When you load a profile for the writer to use, the writer object assigns an input number for each connection in the profile. For more information about loading profiles for the writer, see To Use Profiles with the Writer. Unless you are using mutual exclusion by bit rate, there is one connection for each stream. Streams that are mutually exclusive by bit rate share a single connection.
  2. Your application should identify the input numbers for the file. For more information about identifying input numbers, see To Identify Inputs By Number.
  3. For each input, you should ensure that the input format matches your data. You can enumerate the input formats supported by the SDK. For more information, see To Enumerate Input Formats. You cannot enumerate the input formats of arbitrary streams or streams that are already compressed. For more information about these special cases, see Arbitrary and Precompressed Stream Inputs.
  4. Assign the correct input format for each connection. For more information, see Assigning Input Formats.
  5. Some codec and writer features are configured at encoding time instead of in the profile. To configure these features, you must use input settings. For more information, see To Set Input Settings.

Writing ASF Files