# Analysis

A configuration can contain any number of analysis tasks. For example, you can run face detection and object recognition at the same time.

The following example includes a single analysis task named `OCR`. The task uses the `OCR` analysis engine:

    [Session]
    Engine0=Ingest
    Engine1=OCR

    [OCR]
    Type=ocr
    Input=Default_Image

An analysis engine accepts input of a particular type. For example, the OCR engine requires an image track, and the SpeakerID engine requires an audio track. The analysis engine only processes records from the track specified by the `Input` configuration parameter. In this example, the OCR engine processes the `Default_Image` track produced by the ingest engine. The default value of the `Input` parameter is `Default_Image` for engines that require images and `Default_Audio` for engines that require audio, so in many cases you do not need to include the `Input` parameter in the configuration.

Some analysis engines require more complex input. For example, the face recognition analysis engine requires records that contain an image but also region information that specifies the position of the face in the image. The region information is not available in the `Default_Image` track from the ingest engine so you cannot use that track as the input and you must set the `Input` configuration parameter. The region information is provided by a face detection analysis task. The `DataWithSource` track produced by face detection includes the location of each face in every frame and the corresponding source images.

In the following example the input of the face recognition task is the `DataWithSource` track produced by the face detection task:

    [Session]
    Engine0=Ingest
    Engine1=FaceDetect
    Engine2=FaceRecognize

    [FaceDetect]
    Type=FaceDetect
    ...

    [FaceRecognize]
    Type=FaceRecognize
    Input=FaceDetect.DataWithSource
    ...

The response to `action=ListEngines` describes the type of input required by each analysis engine. It also describes the output tracks that are produced. To be used as the input for a task, a track must provide at least the required record types. For more information about the output tracks produced by Media Server engines, refer to the Media Server Reference.

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