H.264 is an industry standard for video compression, which is the process of converting digital video into a format that takes up less capacity when it is stored or transmitted.
When you allow H.264 decoding, the HTML Access client uses H.264 decoding if the agent supports H.264 encoding. If the agent does not support H.264 encoding, the HTML Access client uses JPEG/PNG decoding.
If you are connected to a remote desktop or published application, you can allow H.264 decoding by turning on the Allow H.264 decoding option in the Settings window, which is available from the sidebar. You must disconnect and reconnect to the remote desktop or published application for the new setting to take effect.
If you are not connected to a remote desktop or published application, you can click the Settings toolbar button in the upper-right corner of the desktop and application selector window and turn on the Allow H.264 decoding option in the Settings window. The new setting takes effect for any sessions that are connected after you change the setting.