So, you publish video from canvas like Canvas Streaming
or Stream Filter
example. In this case, please chek if the stream published may be played from the server (before adding to mixer). Also, please check the stream metrics using /stream/find
POST /rest-api/stream/find HTTP/1.1
metric value is 0 when you adding the remote image from s3, it means that browser stops sending video packets. For canvas streaming to work, the browser thread capturing an image from canvas must be on foreground. For example, if you switch to another browsers tab, canvas streaming will freeze.
So please check how do you downloading image from s3 and drawing on canvas. If download process goes to foreground and canvas drawing goes to background, it may be a reson for stream to freeze.
Another possible reason is channel bandwidth, this may be not enough to download remote image and to publish stream simultaneously. In this case, use the lower canvas resolution.
The last, but not least, please check clients PC CPU load. CPU may be not enough to replace the image background and capture stream from canvas simultaneously.