To export part of an existing Wowza nDVR recording as an MP4, identify the right nDVR store and run Wowza Streaming Engine’s converter: either the REST API action, which accepts UTC start/end timestamps or a duration in milliseconds, or Wowza’s Java converter example, which uses offsets in milliseconds. The parameter formats and time bases differ, so choose the route that fits your integration and confirm the store’s time range before converting.
Before you convert: confirm that the recording exists
nDVR records a live stream as it is ingested by Wowza Streaming Engine. Conversion exports a segment from an existing store; it cannot recover footage that was never recorded. Confirm that nDVR is licensed and configured, and that the source remained connected long enough to create the desired recording. Wowza notes that a disconnected live source may prevent recording. See the Manage nDVR stores guide and nDVR setup documentation.
Playback controls and file extraction are separate operations. Wowza documents DVR playback over HLS and MPEG-DASH, using ?DVR in the playback URL; that does not create an MP4. Use the converter for export.
Choose a conversion route
| Route | Clip boundaries | Version and operational notes |
|---|---|---|
| REST converter action | UTC Unix start/end timestamps by default, or duration in milliseconds. The REST API can use DVR time when explicitly selected. | The guide covers Engine 4.3.0 and later; the API reference lists the converter action in builds 15942 or later. Supports a single store and documented grouped ABR conversion. |
| Java API converter example | startoffset is milliseconds from the store’s beginning; endoffset is milliseconds from its end. |
The example says Engine 4.4.0 and later. It uses a custom HTTP provider enabled in the virtual-host configuration; conversion settings may be cached for up to 30 minutes. |
For a direct documented operation or automation that already uses the Engine REST API, use REST. Use the Java example when you specifically need its Engine-side provider and offset semantics. Do not substitute one route’s endpoint or parameters for the other. References: REST conversion guide, Java API conversion example, and REST API reference.
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Extract a clip with the REST API
- Set your request details. Replace
{serverName},{vhostName},{appName},{instanceName}, and{dvrStoreName}with values from your Engine deployment. The instance name is commonly_definst_, and is the API reference’s default. The guide’s example uses a local Engine endpoint athttp://127.0.0.1:8087; this is a template, not a universal endpoint. Protect the Management API and use the authentication configured for your server. The reference specifies basic authentication. - List stores for the application instance.
curl -u 'username:password' 'http://127.0.0.1:8087/v2/servers/{serverName}/vhosts/{vhostName}/applications/{appName}/instances/{instanceName}/dvrstores'Use the list to locate the store name, then inspect the individual store before choosing clip boundaries.
- Inspect the target store.
curl -u 'username:password' 'http://127.0.0.1:8087/v2/servers/{serverName}/vhosts/{vhostName}/applications/{appName}/instances/{instanceName}/dvrstores/{dvrStoreName}'Review the response’s audio/video availability, live status, DVR time boundaries, duration, UTC boundaries, and conversion status. Make sure the store covers the segment you need.
- Choose one boundary method. For wall-clock selection, pass UTC Unix timestamps as
dvrConverterStartTimeanddvrConverterEndTime. For a clip specified by length, usedvrConverterDurationin milliseconds. Duration cannot be combined with start or end. The REST route uses UTC by default; setdvrConverterTimeType=DVRwhen the supplied start/end values should use DVR time instead. - Send the conversion request. The basic single-store action is a PUT to the store’s
/actions/convertroute. Add the selected converter query parameters as documented for your Engine version.
curl -u 'username:password' -X PUT
'http://127.0.0.1:8087/v2/servers/{serverName}/vhosts/{vhostName}/applications/{appName}/instances/{instanceName}/dvrstores/{dvrStoreName}/actions/convert'Wowza’s guide returns a success message indicating that conversion started; it is not a guarantee that a file is already ready. Use the store and converter status information to check progress. The REST reference also documents options including output filename, output directory, audio/video synchronization, and converter tolerance. The default output directory is based on the application’s StorageDir. Check the reference for the exact parameter names and availability on your build rather than assuming an option is supported everywhere.
Convert an ABR group
For an adaptive-bitrate group, Wowza’s guide uses the application-level /dvrstores/actions/convert route and a comma-separated dvrConverterStoreList query parameter naming the stores to convert. Follow the REST reference’s grouping and option syntax for your build; do not send a grouped request to the single-store route.
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Extract a clip with the Java API converter example
Wowza’s Java example supplies a converter HTTP provider at http://[wowza-ip-address]:1935/converter. This is a separate route from REST and requires compiling the example with the Wowza IDE and enabling the provider in the Engine virtual-host configuration. Follow the Java guide’s deployment instructions for the specific Engine installation.
- Identify the store. Use the applicable stream/store name. For version-archive storage, the Java example says to use the base stream name, not a version-specific suffix, so that all versions are included.
- Set clip offsets in milliseconds. The example’s
startoffsetcounts from the beginning of the nDVR store;endoffsetcounts backward from its end. A zero offset means the beginning or end, respectively. These are not UTC timestamps and do not mean “milliseconds after midnight.” - Issue the conversion command. Use the Java example’s conversion command and parameters against the configured
/converterprovider. Its guide also documents status lookup and cache-expiration commands; use those rather than assuming the REST status route applies. - Check status, then expire stale settings if needed. The example caches conversion request settings for up to 30 minutes. If you repeat a conversion for the same store with changed parameters, clear or expire the conversion cache before expecting the new settings to take effect.
Because this provider is a Java example rather than the REST action, its parameter names, offset meanings, status operation, and cache behavior should be followed as documented in the Java API guide.
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Understand the time basis before choosing boundaries
- UTC time: The REST converter’s default start/end basis. Wowza assigns UTC as packets enter the nDVR module, so it indicates approximately when Wowza received them—not the precise time packets left the encoder.
- 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. Select it explicitly for REST with
dvrConverterTimeType=DVR. - Packet time: Preserves encoder timestamps. It is distinct from both UTC and DVR time; verify the selected API’s documented support and parameter syntax before relying on it.
- Java offsets: Relative to the store’s beginning and end, in milliseconds. They are not interchangeable with REST’s default UTC Unix timestamps.
If a clip must align to a real-world event time, UTC is only an approximate receipt time at Wowza. Confirm the recording’s boundaries and the time basis in the chosen route; do not assume the requested interval guarantees frame-accurate edges or a particular output duration.
Conversion settings and version-sensitive behavior
- REST tolerance: The REST reference documents
dvrConverterTolerancefor Engine 4.7.5 and later, with a default of 1,000 milliseconds. It permits conversion to run past the requested duration while applying the last nDVR GOP; it should not be read as a promise of frame-accurate endpoint timing. - Interleave delay: Available from Engine 4.7.0.01, enabled by default at 100 milliseconds, and adjustable from 0 to 2,000 milliseconds. The guide says higher values increase conversion time while reducing storage I/O saturation.
- Output and synchronization: The REST reference describes output filename, directory, and audio/video synchronization options. Defaults and option availability may vary by Engine build; check the reference for the deployed version.
- Version floor: The REST guide states Engine 4.3.0+, the REST reference lists converter availability from build 15942, and the Java example states Engine 4.4.0+. Check both version and build against the route you use.
Troubleshoot a failed or unexpected clip
| Symptom | Likely cause | What to check or do |
|---|---|---|
| No suitable store appears | nDVR was not recording, the source disconnected, or the wrong application instance was queried. | Confirm nDVR configuration and source continuity, then list stores for the correct server, vhost, application, and instance. |
| The clip starts or ends at the wrong moment | UTC Unix timestamps, DVR time, and Java offsets were confused, or UTC was treated as encoder departure time. | Check the store’s UTC and DVR boundaries. Use the intended time basis and the parameter format for the selected route. |
| Duration parameter is rejected | dvrConverterDuration was combined with start or end. |
Use duration alone, or remove it and specify a valid start/end pair. |
| Repeated Java conversion uses old boundaries | The example’s per-store settings cache may still be active. | Use its cache expire command before retrying changed parameters; the documented cache period is up to 30 minutes. |
| Output is missing or not where expected | The conversion may still be running, the target store may be invalid, or output directory assumptions may be wrong. | Check conversion status, store details, and the application’s StorageDir and configured output options. |
| Requested edge does not match an exact frame | nDVR GOP handling and converter tolerance can affect the endpoint. | Review the version-specific tolerance behavior and treat the requested boundary as a selection target, not a guaranteed frame-exact cut. |
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