IEncoderAPI Interface

Microsoft DirectShow 9.0

IEncoderAPI Interface

  • Note   This interface is deprecated and is maintained for backward compatibility only. New applications and drivers should use the ICodecAPI interface.

The IEncoderAPI interface defines a standard way for applications and drivers to communicate with third-party hardware or software encoders that implement the interface. For more information on this interface, see Encoder API.

In addition to the methods inherited from IUnknown, the IEncoderAPI interface exposes the following methods.

Methods Description
GetDefaultValue Retrieves the default value for a parameter, if one exists.
GetParameterRange Retrieves the valid range of values that the parameter supports, in cases where the parameter supports a stepped range as opposed to a list of specific values.
GetParameterValues Retrieves the list of values supported by the given parameter.
GetValue Retrieves the current value of a specified parameter.
IsAvailable Queries whether a given parameter is available.
IsSupported Queries whether a given parameter is supported.
SetValue Sets the current value of a parameter.


In the various interface methods, the following GUIDs, defined in uuids.h, are used to indicate which parameter is being set or retrieved.

Parameter Description
ENCAPIPARAM_BITRATE Specifies the bit rate, in bits per second. In constant bit rate (CBR) mode, the value gives the constant bitrate. In either variable bit rate mode, it gives the average bit rate. The value is a 32-bit unsigned long.
ENCAPIPARAM_PEAK_BITRATE Secifies the peak bit rate. This parameter is relevant only when ENCAPIPARAM_BITRATE_MODE has been set to VariableBitRatePeak.
ENCAPIPARAM_BITRATE_MODE Specifies the bit-rate mode, as a VIDEOENCODER_BITRATE_MODE enumeration value (32-bit signed long).

The following table describes the expected behavior of an encoder under extremely high or low bitrate conditions in the two variable bitrate modes defined in VIDEOENCODER_BITRATE_MODE.

Condition Mode Behavior
Scene falls to black or there is zero motion VariableBitRateAverage Over a short period of time (several seconds) the bit rate will fall below the rate specified for the ENCAPIPARAM_BITRATE parameter. But over a four-minute period of time, the encoder will maintain the average rate, if necessary by adding "dummy" bits to the stream.
Scene falls to black or there is zero motion. VariableBitRatePeak The bitrate will fall below the expected rate as specified in the value for the ENCAPIPARAM_BITRATE parameter. The rate will stay at that level until a more complicated scene begins.
The scene is extremely complex. VariableBitRateAverage For a few seconds the rate will go up. If the scene stays complex, the rate will come back down and the picture will become blocky in order to maintain the average as specified in the value for the ENCAPIPARAM_BITRATE parameter.
The scene is extremely complex. VariableBitRatePeak The rate will go up and stay up, possibly above the expected rate as specified in the value for the ENCAPIPARAM_BITRATE parameter, but never above the peak as specified in the ENCAPIPARAM_PEAK_BITRATE parameter.

OCUR Devices: This interface supports OpenCable Unidirectional Cable Receiver (OCUR) devices. See OCUR Devices.


Header: Declared in Strmif.h; include Dshow.h.

Library: Use Strmiids.lib.

See Also