Configure video previews

How video previews work in Censhare and how to configure them correctly to avoid compatibility issues.

Introduction

By default, video previews are based on the master file of the asset. Not all video formats are supported; a comprehensive list of supported formats is also not possible. It is recommended to configure an automatic generation of a preview file in the MP4 format by enabling a video transcoding service. MP4 is known to be compatible with most of the modern browsers and devices.

How video previews work in Censhare

censhare Web uses HTML5 and the MediaElement.js library for showing preview videos. The censhare Client (aka Java Client) uses the native web browser of the operating system for displaying video previews. As in censhare Web, HTML5 is used for this purpose. The censhare Client embeds a video in the HTML5 code and then shows it in a browser window.

How to configure video previews

A complete configuration includes the following steps. Some of them are optional because any Censhare system is delivered with a few things pre-configured. However, you still need to “glue” them all together to make sure the incompatibility problems won‘t appear.

1. Choose and set up a transcoding service. See also Overview of transcoding services

2. (Optional) Create additional presets. FFmpeg comes with six preconfigured presets as described here. If you use another transcoding service or if you need other presets for a different reason, you can add them in form of the XML files in the censhare-Server/install/assets/optional/preset-ffmpeg folder. For AWS, you will have to configure presents as part of the general setup.

3. Configure presets. For presets to be used in services, you need to select them in the configuration.

Support for timecode format

Timecode support allows referencing video frames on video assets instead of simple timestamps.

The format for the start and end time is hh:mm:ss:ff: the last two positions of the timecode show the video frame. 

If you see a semicolon (;) instead of a colon (:) before the video frame, then the frame is a floating number, e.g. 0.002 and not the full number. It is also known as a drop frame and is widely used in TV broadcasting. The purpose is to sync with real time. Consequently, some frame numbers (but not frames) are “dropped”.

Discrepancy between video length in different widgets for existing video assets

Timecode support introduced with the release 2025.1 used to have a small bug.

Previously,the displayed number of frames has been rounded down for the master file used in the Editor. Consequently, in the Editor, the existing video assets may appear as one frame shorter than in the Preview and Annotation widgets (Overview and Communication tabs respectively).

To fix this, please run the Create Previews server action. Any new assets are not affected by the problem and does not require a fix.