有关于VOD视频点播系统的英文文章吗

Push video on demand is a technique used by a number of broadcaster on systems that lack the interactivity to provide true video on demand, to simulate a true video on demand system. A push VOD system uses a Personal Video Recorder (PVR) to automatically record a selection of programming, often transmitted in spare capacity overnight. Users can then watch the downloaded programming at times of their choosing. As content occupies space on the PVR hard drive, downloaded content is usually deleted after a week to make way for new programmes. The limited space on a typical PVR hard drive means that the flexibility and selection of programmes available on such systems is more restricted than true VOD systems.