New in Flash Professional CC 2015
In addition to FLV videos, this release also introduces an option to embed H.264 videos in the timeline. When an H.264 video is embedded, the frames of the video are rendered on the stage when you scrub the timeline. This feature enables you to use videos as a guide to synchronize your animation on stage. Since the Flash Player and other run-times do not support rendering embedded H.264 videos, they are not published. Importing H.264 videos is a design-time-only feature.
Audio playback is enabled for H.264 videos. You can now select the ‘Include audio’ option while importing H.264 videos. Once imported to the stage (with ‘place instance on stage’ option selected), scrubbing the timeline must play the audio for the relevant frames. Playing the timeline (Enter) must play back the animation at the fps of the imported video so that the audio is in sync with the video frames on stage.
To learn more about importing H.264 videos, see Add videos to Flash.
To import video:
Click File > Import > Import Video and select the Embed H.264 video in the timeline  (design time only – the video cannot be exported) option as shown in the following image: