The Tool Desk
Outbyte Driver Updater FREEScan for outdated or missing drivers - takes under a minuteDriver Scan →Outbyte PC Repair FREERepair Windows errors before they cause bigger problemsFix Now →To export part of an existing Wowza nDVR recording as an MP4, identify the correct nDVR store and call Wowza Streaming Engine’s REST converter action with the clip boundaries. REST start and end values use UTC Unix timestamps by default; duration is in milliseconds and cannot be combined with start or end. Wowza’s separate Java API example selects a clip with offsets in milliseconds from the store’s boundaries. Choose one route and use its time semantics consistently.
Before you convert: confirm that an nDVR store exists
Clip extraction converts footage already recorded in an nDVR store; it cannot recover material that was never recorded. Wowza nDVR records a live stream as it is ingested, so first confirm that nDVR is licensed and configured for the application and that the source was connected while the desired footage was being recorded. Wowza notes that a disconnected live source may prevent recording. See the Wowza guide to managing nDVR stores and its nDVR setup documentation.
Playback support and file export are different operations. Wowza documents nDVR playback with controls over HLS and MPEG-DASH, using ?DVR in the playback URL; that does not itself create an MP4. For an MP4 clip, use a converter operation.
Choose the API route that fits your integration
| Route | Clip selection | Version and operational notes |
|---|---|---|
| REST converter action | UTC Unix timestamps for start/end by default, or duration in milliseconds; the time type can be set to DVR. | The guide covers Engine 4.3.0 and later; the REST reference lists the converter action for builds 15942 or later. Supports a single store and grouped ABR stores. |
| Java API converter example | startoffset and endoffset in milliseconds, measured from the beginning and end of the store respectively. |
The example requires Engine 4.4.0 or later, uses a custom HTTP provider, and caches conversion settings for up to 30 minutes. |
Use REST when you want to invoke the documented store action directly. Use the Java example when an Engine-side custom provider matches your integration. The Java provider endpoint and parameter names are not interchangeable with REST. Sources: REST conversion guide, Java API example, and REST API reference.
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Extract a clip with the REST API
1. Set up the request safely
The REST API uses basic authentication. Run requests against your own Engine endpoint and substitute your server, vhost, application, instance, and store names; Wowza’s guide illustrates a local endpoint at http://127.0.0.1:8087, which is an example rather than a universal address. Do not expose the management API publicly without appropriate access controls, and do not put real credentials in shared scripts or logs.
The route pattern for listing stores is:
GET http://127.0.0.1:8087/v2/servers/{serverName}/vhosts/{vhostName}/applications/{appName}/instances/{instanceName}/dvrstoresIn the route, {instanceName} is commonly _definst_ when using the default instance; use the actual instance configured for your application.
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2. Find and inspect the store
- List the application’s nDVR stores using the route above.
- Inspect a specific store by appending
/{dvrStoreName}to that path. - Check the returned audio/video availability, live status, DVR time boundaries, duration, UTC boundaries, and conversion status. Confirm that the target store covers the portion you intend to export.
3. Call the converter action
For one store, send a PUT to the inspected store’s path with /actions/convert appended:
PUT http://127.0.0.1:8087/v2/servers/{serverName}/vhosts/{vhostName}/applications/{appName}/instances/{instanceName}/dvrstores/{dvrStoreName}/actions/convertThe documented guide’s successful response indicates that conversion has started; it is not a promise that the file is already finished. Use the store/conversion status exposed by the API to check progress and result. Consult the conversion guide and API reference for the exact request syntax supported by your Engine build.
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4. Set boundaries and output options
- Start and end:
dvrConverterStartTimeanddvrConverterEndTimeare UTC Unix timestamps by default. Use them when selecting a wall-clock interval, while remembering UTC here is the time Wowza assigned as packets entered nDVR, not an exact encoder departure time. - Duration:
dvrConverterDurationis in milliseconds. It cannot be combined with start or end parameters. - Time basis:
dvrConverterTimeType=DVRselects DVR time rather than the default UTC basis. Be explicit about the chosen basis before calculating boundaries. - Output name and location: The REST reference documents an output filename option and a default output directory based on the application’s
StorageDir. Check the reference for the parameter names and confirm the resulting location in your installation. - ABR group: To convert a group of stores, the guide uses
/dvrstores/actions/convertand the comma-separateddvrConverterStoreListquery parameter rather than the single-store action route. - Tolerance: On Engine 4.7.5 and later,
dvrConverterToleranceis documented with a default of 1000 milliseconds. It allows conversion to run past the specified duration while applying the last nDVR GOP; do not assume this guarantees a frame-exact endpoint. - Interleave delay: Available from Engine 4.7.0.01, the delay is enabled by default at 100 ms and can be set from 0 to 2000 ms. Higher values increase conversion time while reducing storage I/O saturation.
Understand the time values before choosing a clip
The REST API’s default UTC timestamps, DVR time, packet time, and Java example offsets describe different clocks or reference points. They should not be substituted for one another.
- UTC time: The REST default. Wowza assigns it as packets enter the nDVR module, so it is only a rough indication of when Wowza received content—not an exact timestamp of when the encoder sent it.
- DVR time: Begins at zero and advances in milliseconds. It does not include gaps when a source stops sending or when append mode is used. The REST converter can select this basis with
dvrConverterTimeType=DVR. - Packet time: Preserves encoder timestamps. If aligning to media timestamps matters, confirm the time type supported by your selected operation and how the source timestamps are generated.
- Java offsets: In Wowza’s Java example,
startoffsetis measured from the beginning of the store andendoffsetfrom its end, both in milliseconds. A zero value means use the corresponding store boundary.
For a clip tied to a real-world clock time, verify the store’s UTC boundaries and use the REST default knowingly; UTC reflects packet arrival at Wowza approximately. For elapsed recording position, DVR time or the Java offsets may be more appropriate, depending on the route and the boundary you intend to anchor.
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Use the Java API converter example
Wowza’s Java API article provides a custom converter HTTP provider example. It is compiled with the Wowza IDE and enabled in the Engine virtual-host configuration. The example endpoint is http://[wowza-ip-address]:1935/converter; it is not the REST API route. Follow the Java API guide for provider setup and its convert, status, and expire commands.
For that provider, specify startoffset and endoffset in milliseconds using the example’s opposing reference points: start offset from the store’s beginning, end offset from its end. The example warns that conversion settings are cached for a store for up to 30 minutes. If you change parameters and repeat a request, expire or clear the conversion cache before expecting the new settings to apply. In version-archive storage, use the base stream name rather than a version-specific suffix to include all versions.
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Common problems and fixes
- No store appears: Confirm the application and instance in the route, nDVR configuration and license, and whether the source was connected and recorded during the requested period.
- Clip boundaries are wrong: Check whether REST values were interpreted as UTC Unix timestamps or DVR time, and verify milliseconds versus seconds. For the Java provider, calculate offsets from the correct store edge rather than passing REST timestamps.
- Duration request is rejected: Do not send
dvrConverterDurationtogether with start or end values; choose duration or boundary parameters. - Updated Java parameters appear ignored: Expire the cached conversion settings for the store; the example documents caching for up to 30 minutes.
- Conversion does not start: Check basic authentication, the HTTP method and route, the actual server/vhost/application/instance/store names, and that your Engine build supports the converter action.
- Expected footage is absent: Extraction cannot create missing recording data. Check the store’s reported span and source connectivity; Wowza warns that a disconnected source may prevent recording.
- Output is not where expected: Check the configured application
StorageDirand any explicit output filename/directory options in the REST reference.
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