Thank you for contacting the JW Player support team. Sometimes an upgrade of Flash is needed to resolve this problem since RTMP at its core is Flash-based. Also, the following bullet points may be a of use:
Please make sure you are using these settings in your encoding: http://support.jwplayer.com/customer/portal/articles/1403635-media-format-reference#video/. Some browsers are more stringent than others about encoding requirements. I typically use Handbrake (free on Mac) to encode video files.
Here are a few screenshots of my encoding settings:
Please make sure that the request for your video is returning a proper mime-type that corresponds to your video format:
3) Hardware acceleration:
IE has a browser setting called ‘hardware acceleration’ which has been known to break some videos. You can disable hardware acceleration with our player by using ‘stagevideo’: false in your setup configuration (or you can disable the setting in your browser).
4) Mov Atom
The ‘moov’ atom in your video encoding. This is basically a piece of metadata that tells a video player when the video is ready to play. When creating web-friendly video, it is important to select a ‘web optimized’ or fast-start settings.
If you are using ffmpeg, you can use the following:
ffmpeg -i input.mp4 -codec copy -map 0 -movflags +faststart output.mp4
5) Pseudo-Streaming with Flash
If you’re serving videos to clients with older browsers that need Flash mode, you may need to enable psuedostreaming:
Randy Le’Moine, Web Support Engineer, JW Player