UMSVideoDecoderMClass Class

Ultimedia Services Version 2 for AIX: Programmer's Guide and Reference

UMSVideoDecoderMClass Class

The UMSVideoDecoderMClass class is a metaclass that defines the class methods for children of the UMSVideoDecoder base class. In particular, UMSVideoDecoderMClass specifies creation methods for UMSVideoDecoder objects.

To learn more about the UMSVideoDecoderMClass class, see:

For introductory information, see MetaClass Objects.

Enumeration Lists

To avoid name collision on defines, integer values have been captured as enumeration lists. The set of valid values from an enumerated list can vary with the application. The detailed method descriptions describe the valid or possible values for the specific use. The enumerated lists that are defined for this object are listed as follows:

enum ReturnCode {
   Success, 
   Failure, 
   FatalUMSError, 
   NoConfigObject,
   AliasNotFound, 
   PropertyNotFound,
   InvalidClassName, 
   NotAChild, 
   UnsupportedFormat,
   MemoryError
   };

Method Descriptions

UMSVideoDecoder make_by_transformation(in string from_format, in string to_format, inout ErrorCode error, out string error_string)

Description

This method returns an instantiated child of the UMSVideoDecoder class as determined by the from_format and to_format parameters. The particular child returned depends upon interaction with a UMSConfig object.

Arguments

in string from_format	Specifies the alias to seek using the UMSConfig object.
in string to_format	Specifies the alias to seek using the UMSConfig object.
inout ErrorCode error	Provides success or reason for failure. If a failure occurs, then a null pointer is returned instead of an instantiated object
out string error_string	If an error occurs, this string contains detailed information about the point of failure.

Error Codes

For certain Error Codes, more specific information can be obtained from the error_string parameter.

Error Code	error_string
Failure	Name of the class that failed to be created.
AliasNotFound	Alias that could not be found by the UMSConfig object.
PropertyNotFound	Property that could not be found by the UMSConfig object.
InvalidClassName	Name of the class that could not be found by the SOM runtime.
NotAChild	Name of the class that is not a child of the UMSVideoDecoder base class.

UMSVideoDecoderMClass Usage

The VideoDecoderMClass uses the configuration file to determine that subclass of the VideoDecoder class to instantiate. The make_by_transformation method first attempts to find an alias that matches the concatenation of TO and the to_alias parameter. If this is found, it checks the video_format_qualifier property of each clause until it finds one that matches the from_alias parameter. The CLASS_UMSVideoDecoder property indicates that particular VideoDecoder subclass to instantiate.

TORGB8Dither:
       video_format_qualifier     "IBMUltimotion"
       CLASS_UMSVideoDecoder      "UMSUMVideoDecoder"
*NEXT:
       video_format_qualifier     "IBMMotionJPEG"
       CLASS_UMSVideoDecoder      "UMSJPEGVideoDecoder"
*NEXT:
       video_format_qualifier     "IBMRTV2"
       CLASS_UMSVideoDecoder      "UMSRTV2VideoDecoder"
*NEXT:
       video_format_qualifier     "IBMRTV21"
       CLASS_UMSVideoDecoder      "UMSIndeoVideoDecoder"

For introductory information, see MetaClass Objects.