The phrase "on the fly" appears in many articles on streaming technology and some tutorials about streaming engines like Wowza and Unified Streaming. But what does the phrase mean?
"On the fly" related to streaming usually refers to processing of live streams and delivery of modified result with low latency (almost in real time).
This can include encoding with different codecs, bitrate (transcoding), packetising streams (for delivery as HLS, MPEG-DASH and similar formats available over HTTP).