Is it possible to delete the video which is chosen to the VOD/Live streaming from the library? And is there any impact to that VOD/Live streaming?
If it is selected for simulive (in the case of "Preparing", "Scheduled" to "Closed" status), or if the status is "Encoding" for VOD streaming, the following error will be displayed and deletion will not be possible.

If there is no possibility to reuse the same video on same simulive again, please archive that live event once status is changed to "Ended". Or please replace the simulive File with another video and save as new live event, then video can be deleted.