Modifying the Simultaneous Transcoding Session Limit
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Affected Roles: Owner, Administrator
Related Digital Watchdog VMS Apps: DW Spectrum IPVMS
Last Edit: January 23, 2023
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What is a Transcoding Session?
Transcoding is the process of taking compressed or encoded content, then decompressing or decoding it and modifying it in some way. The data is then re-compressed or encoded. The most common scenario where this is done is when decreasing the resolution and bitrate/framerate of camera video. This can sometimes include changing a video or audio format from one to another (e.g., MJPEG to H.264), or when adding watermarks to video.
A transcoding session is an example of this process where you need to transcode multiple things, creating the need for multiple sessions to transcode everything simultaneously. This session is initiated when the Get/media/<cameraID>.<format> API call is made with WEBM and MPJPEG format links using a custom-resolution parameter.
**NOTE: Increasing the transcoding session can lead to the CPU to become overloaded. It is not recommended to increase the transcoding session limit unless you know that your hardware is suitable for the task.
Transcoding Session Limit
At the onset of DW Spectrum 4.0, a default limit of no more than two (2) simultaneous transcoding sessions was set. This limit was put in place to avoid CPU overload issues that had been observed occurring at installation sites that had a Progressive Downloading API call enabled. As a result, this change may have broken some integrations that relied on more than two (2) simultaneous transcoding sessions at a time.
**NOTE: The use of Intel QuickSync to enable more streams was tested by developers in experimental builds and it was found that it introduced additional graphic issues when implemented. Use of QuickSync has been put on an indefinite hold and not recommended.
Increasing Simultaneous Transcoding Session Limit
To increase the number of simultaneous transcoding sessions, Administrator-level role permissions are required to make the change.
To make the changes:
- Modify the following address for your site and enter it into your browser.
<server_address>:<server_port>/#/settings/advanced
- To increase the limit, on the Advanced settings page, search for the maximum amount of HTTP connections when using transcoding for the server.
If Chrome opens two (2) connections at once, close the first connection.
- Modify the value of the “maxHttpTranscodingSessions” parameter.
It is recommended to set value > =2 for the transcoding session parameter.
- Select Save to confirm your changes.
- Restart the DW Spectrum Server and test the new parameter setting.
For More Information or Technical Support
DW Technical Support: 866.446.3595
https://www.digital-watchdog.com/contact-tech-support/
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