Sorry, without root, is probably not possible. With your device's OS version and the fact that you want to capture an overlay (video playback), even harder.
Prior to Android 3.0, screenshots were taken using the framebuffer, that is accessed by opening the /dev/graphics/fb0 device. This location requires root access, and even with root may not work for all devices. Some devices use a pair of framebuffers and toggle between them.
Additionally, and more related with your current problem, the framebuffer doesn't contain surfaces in an overlay (often the case with video playback). That's the reason as to why you don't get the video, only the application frame.
Support information by developers on stackoverflow by this answer and this answer.