Specific Alias Stanza Types

Use of the configuration file evolves with increasing alias stanza types and properties. This section describes the alias stanza types and properties of the default configuration file.

To learn more about alias stanza types, see:

• Audio Device Alias
• Audio Inputs Alias and Outputs Alias
• Audio Formats Alias and Video Formats Alias
• Detector Alias
• File Type Alias
• TO<Format> Alias

For introductory information, see Programming with Configuration Objects.

Audio Device Alias

An audio device alias can have multiple clauses where each clause defines properties of a specific audio device. An audio device alias must minimally contain the properties:

device_path             "<device>" 
CLASS_UMSAudioDevice    "<object_name>"
audio_formats_alias     "<formats_alias_name>"
audio_inputs_alias      "<inputs_alias_name>"
audio_outputs_alias     "<outputs_alias_name>"

Where:

• device string defines the path name to the desired audio device to be used; for example, /dev/acpa0.
• object_name string defines the class name of the specific UMSAudioDevice object to be used to access the device; for example, UMSACPADevice.
• formats_alias_name, inputs_alias_name, and outputs_alias_name strings provide alias names for the device's audio_formats_alias, audio_inputs_alias, and audio_outputs_alias that title alias stanzas which describe the device's capabilities.

Audio Inputs Alias and Outputs Alias

The audio_inputs_alias and audio_outputs_alias names found in the audio device alias are used to list the sets of input connections and output connections that the device object supports. These connections are listed as properties of the respective alias. For example, if the audio_inputs_alias is UMSACPAInputs, the alias stanza might be:

UMSACPAInputs:
 LINE_IN         "<don't care>"
 LOW_GAIN_MIC    "<don't care>"
 HIGH_GAIN_MIC   "<don't care>"

In this case, only the property names are significant. The property value is not of interest.

Audio Formats Alias and Video Formats Alias

The audio formats alias is used to list the formats that an object supports. The formats supported are listed as property names under the alias with the property names being string values the device object supports as audio formats. If the audio_formats_alias for a device is UMSACPAFormats, the alias stanza might be:

UMSACPAFormats:
        PCM     "PCM" 
        A_LAW   "A_LAW"
        MU_LAW  "MU_LAW"
        ADPCM   "IBMADPCM4E"

Unlike the audio input or audio outputs alias stanza, the value strings for these property names are significant. The value string is used to confirm format matches between objects. For example, file objects and device objects advertise their supported formats in alias stanzas. Equality of value strings signifies a format match even if the property names are different. Inequality of the value string signifies that the formats are not the same even if the property names are the same. In this case, the value string is referred to as a format qualifier.

Video formats alias stanzas are similarly phrased. For example, if the video_formats_alias for an object is UMSAVIVideoFormats, the alias stanza might be:

UMSAVIVideoFormats:
        ULTI     "IBMUltimotion"
        JPEG     "IBMMotionJPEG"
        mJPG     "IBMMotionJPEG"
        RTV2     "IBMRTV2"
        RT21     "IBMRTV21"
 

Detector Alias

A detector alias stanza typically has multiple clauses where each clause specifies a detection module to be applied in the detection process. Each clause in a detection alias stanza must contain the following property names:

detection_module        "<pathname>"
file_type_alias         "<file_type_alias_name>"

Where:

• pathname string defines the pathname to a detection module,
• file_type_alias_name provides an alias name for the file type. Note that this file type alias stanza should be in the configuration file also.

File Type Alias

A file type alias stanza defines properties of a specific file access object. An audio file type alias stanza must contain the properties:

CLASS_UMSAudioFile        "<object_name>"
audio_formats_alias       "<formats_alias_name>"

Where:

• object_name string defines the specific class of UMSAudioFIle that should be used to access the file.
• formats_alias_name is the audio_formats_alias alias name. Note that this alias should be in the configuration file and is used to list the formats supported by the file format.

A movie file type alias stanza must contain the property names:

CLASS_UMSMovieFileReader         "<object_name>"
audio_formats_alias              "<formats_alias_name1>"
video_formats_alias              "<formats_alias_name2>"

Where:

• object_name string defines the specific class of UMSMovieFileReader that should be used to access the file.
• formats_alias_name1 and formats_alias_name2 specify the alias names of the stanzas which define the supported audio and video formats for the file type.

TO<Format> Alias

A TO<Format> alias stanza typically has multiple clauses where each clause defines a from format and an object to convert data to the Format. Each clause must contain the property names:

<data_type>_format_qualifier     "<qualifier>"
CLASS_<object_type>              "<classname>"

Where:

• Format is the format qualifier used to describe the desired output format.
• data_type is audio or video.
• qualifier is the format qualifier used to describe the input format.
• object_type is the class name of the base class to be created (such as UMSFilter or UMSVideoDecoder).

For example, if the TO format for audio data is PCM16, a TO<Format> alias stanza could be:

TOPCM16:
  audio_format_qualifier         "IMAADPCM"
  CLASS_UMSFilter                "UMSADPCMtoPCM16"
*NEXT:
  audio_format_qualifier         "IBMADPCM4E"
  CLASS_UMSFilter                "UMSADPCM4EtoPCM16"

For introductory information, see Programming with Configuration Objects.