If your stream is published using 1024×768 (4:3) aspect ratio, the player will have two black lines on the left and on the right. This is caused because the player default aspect ration is 16:9.
You can try updating the resolution on the camera to publish in a 16:9 aspect ratio and see if you prefer that view over the current feed published in 4:3.
More details about resolution aspect ration you can check on Wikipedia:
Note: the player reports the resolution by clicking on it and hitting CTRL+ALT+F
Below you can see some examples of different videos played in a 16:9 player:
- 16:9 aspect ratio of the video – HD video standard
- 4:3 aspect ratio of the video – Computer monitor standard
- 24:1 aspect ratio of the video – Widescreen cinema standard
For more information regarding different resolutions and aspect ration, you can check the following page: http://en.wikipedia.org/wiki/Display_aspect_ratio.