Appendix A. Using a MediaHub Archive System
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## Appendix A. Using a MediaHub Archive System

This appendix contains information about MediaHub assets that can be brought into VCP-Recorder or that were created by storing a VCP-Recorder clip in the archive system. The following topics are discussed:

- “About MediaHub Clip Groups”

- “Bringing MediaHub Clips Into VCP-Recorder”

- “Finding MediaHub Clips”

- “Storing VCP-Recorder Clips in MediaHub”

This chapter includes examples of MVCP commands, which are described in detail in Chapter 4, “MVCP Reference.” The examples assume that a telnet connection has been made to the VCP-Recorder server. (For an example of a telnet session, see “Establishing an Interactive MVCP Connection”.)

This appendix assumes that you are already familiar with the following:

- the VCP-Recorder graphical user interface (GUI), as described in Chapter 2, “Using the VCP-Recorder GUI”

- MediaHub assets, as described in the MediaHub User's Guide

## About MediaHub Clip Groups

In order for VCP-Recorder to be able to bring an asset into VCP-Recorder, the asset must be a MediaHub group asset that is known as a “clip group.” A clip group is an asset that has a `ClipId` attribute whose value is the name of the clip. The members of the clip group consist of the assets that contain different digital formats of the clip.

| Note: When VCP-Recorder requests an asset from MediaHub, it requests the asset by sending MediaHub the value of the `ClipId` attribute.

The `DasAsset::Format` attribute of the clip group can be /group/multiformat or /group/format.

Multiformat clip groups (that is, clip groups whose format is /group/multiformat) contain one or more formats of a clip. Each member of a multiformat clip group can be one of the following:

- An atom, if the digital format does not require an index.

- A group whose `DasAsset::Format` is /group/format, if the digital format requires an index. Members of each of these group assets are the atom asset that contains the clip's content and the atom asset that contains the index.

If the `DasAsset::Format` attribute of the clip group is /group/format, the clip group contains a single format of the clip. The clip group always has a member atom that contains the content. If the digital format requires an index, the clip group also has a member atom that contains the index.

Figure A-1 shows the structure of a multiformat clip group that contains the MPEG-2 and uncompressed Rice formats of a movie; each of these formats requires an index. The values of the MediaHub `DasAssetId` and `DasAsset::Format` attributes are shown, along with the value of the `ClipId` attribute. Notice that only the clip group asset has a `ClipId` attribute.

Figure A-1. MediaHub Multiformat Clip Group

Figure A-2 shows the structure of a single-format clip group that contains the MPEG-2 format of a movie. The values of the MediaHub `DasAssetId` and `DasAsset::Format` attributes are shown, along with the value of the `ClipId` attribute. Notice that only the clip group asset has a `ClipId` attribute.

Figure A-2. MediaHub Single-Format Clip Group

## Bringing MediaHub Clips Into VCP-Recorder

If a MediaHub clip group adheres to the structure described in “About MediaHub Clip Groups”, you can use the VCP-Recorder GUI or the MVCP `AGET` (Archive Get) command to request that the clip be brought into VCP-Recorder. When you make such a request, the following steps are performed:

1. Through the GUI or the MVCP command, you specify the value of the `ClipId` attribute for the MediaHub clip group. This clip group must contain a format that is compatible with the VCP-Recorder (for example, variable-frame, Rice-compressed for a VCP-Recorder that runs on an Origin2000 with DIVO).

2. VCP-Recorder sends a command to the archive system to determine whether an asset with a `ClipId` attribute containing the specified clip name exists. (VCP-Recorder communicates with MediaHub by sending it Asset Transfer Service commands.)

3. If the clip group does not exist, VCP-Recorder writes an error message to its log.

4. If the clip group exists, VCP-Recorder requests information about the formats of the members in the clip group.

   - If a compatible format does not exist, VCP-Recorder writes an error message to its log.

   - If a compatible format exists, VCP-Recorder copies the content and index (if it exists) from the archive system into its clip cache.

For example, assume that the clip group shown in Figure A-2 exists in an attached MediaHub archive system and that it contains a suitable format. The following example illustrates how the `AGET` command is used to bring that clip into VCP-Recorder:

    AGET DEMO2
    200 OK

## Finding MediaHub Clips

You can use VCP-Recorder to determine if a clip exists in an attached archive system using either the VCP-Recorder GUI or the MVCP `AFND` (Archive Find) command. The clip group must adhere to the structure described in this appendix and it should contain a suitable media format (for example, variable-frame Rice-compressed for a VCP-Recorder that runs on an Origin2000 with DIVO).

The following example uses the `AFND` command to determine that the clip named DEMO2 exists in the MediaHub host named mhub_host:

    AFND DEMO2 mhub_host
    201 OK
    mediahub mhub_host

## Storing VCP-Recorder Clips in MediaHub

You can use the VCP-Recorder GUI or the MVCP `APUT` (Archive Put) command to request that a VCP-Recorder clip be stored in an attached archive system. When you make such a request, the following steps are performed:

1. Through the GUI or the MVCP command, you specify the name of the clip that you want to store in the archive system.

2. VCP-Recorder sends a command to the archive system to determine whether an asset with a `ClipId` attribute containing the specified clip name exists. (VCP-Recorder communicates with MediaHub by sending it Asset Transfer Service commands.)

   - If the clip group does not exist, VCP-Recorder creates a new multiformat clip group containing the new format[5] . It then copies the digital media content and the index file (if it exists) to the archive system.

   - If the clip group exists but it does not contain the targeted media format, VCP-Recorder creates a new single-format group that is added as a member of the MediaHub clip group. It then copies the digital media content and the index file (if it exists) to the archive system.

   - If the clip group exists and it contains the targeted media format, VCP-Recorder requests that the files that contain the content and index for that format be truncated. It then copies the digital media content and the index file (if it exists) to the archive system, replacing the originals.

   - If any MediaHub group assets were created, VCP-Recorder requests that the appropriate member assets be added to those group assets.

For example, the following uses the `APUT` command to store the clip named DEMO3 into the specified archive system:

    APUT DEMO3 mhub_host
    200 OK

[5] The names of MediaHub assets created by VCP-Recorder are generated automatically by the system.

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