Choosing an Encoding Method
[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 It has been superseded by Source Reader and Sink Writer.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 codecs, like the Windows Media Video 9 codec, support multiple encoding methods. The encoding method that you choose for a stream will depend upon how the stream is to be delivered. The following table describes when to use the various encoding methods.
| Encoding method | Description |
|---|---|
| 1-pass Constant Bit Rate (CBR) | The only option for live streaming. Encodes to a predictable bit rate and delivers the lowest quality of all encoding methods. |
| 2-pass CBR | Use for files that will be streamed over a network to a client reader, but that are not broadcast from a live source. Encodes to a predictable bit rate, but with better quality than 1-pass CBR. |
| 1-pass Variable Bit Rate (VBR) | Use when you need to specify the quality of the encoded output. Delivers the most consistent quality of all encoding methods. Use only for local files or for downloading. |
| 2-pass VBR – unconstrained | Use when you need to specify a bandwidth, but fluctuations around the specified bandwidth are acceptable. For local files or downloading only. |
| 2-pass VBR – constrained | Use under the same circumstances as unconstrained, but when you need to specify a maximum momentary bit rate. For local files or downloading only. |
The following table lists the encoding methods that are supported by the codecs that ship with the Windows Media Format SDK.
| Codec | CBR | 2-pass CBR | VBR | 2-pass VBR |
|---|---|---|---|---|
| Windows Media Video 9 | X | X | X | X |
| Windows Media Audio 9 and later | X | X | X | X |
| Windows Media Video 9 Screen | X | X | ||
| Windows Media Audio 9 Voice | X | |||
| Windows Media Audio Professional | X | X | X | X |
| Windows Media Audio Lossless | X | |||
| Windows Media Video 9 Image and later | X | X | ||
| Windows Media Video 9 Advanced Profile | X | X | X | X |
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