This inventions relates to devices which store movies for playback viewing and, more specifically, to video server systems which supply movies on demand.
VCRs are widely used to see movies at the very moment their viewing is desired. This requires each user to possess a relatively expensive piece of hardware, namely the VCR. Each user must also possess a video cassette of the movie which he wishes to see. This is an additional expense and inconvenience. This expense and inconvenience grows as each user attempts to keep up with the new movies which are released. It also grows when each user wishes to stock a large number of movies for possible viewing.
One technology which has been developed to help solve these problems is to supply electronic signals containing each requested movie from a centralized location. These xe2x80x9cvideo-on-demandxe2x80x9d systems are becoming quite popular in hotels. They are also beginning to appear in larger scale systems, such as Community Cable Television (xe2x80x9cCATVxe2x80x9d).
One technique for supplying video-on-demand from a central location is to house and operate a large number of video recorders at the central location. When a particular movie is desired to be viewed, the user communicates with the central location and requests that the movie be played. The video cassette containing the movie is inserted into a video player to which the user is connected.
Such a system still has a substantial cost per user. The equipment needed to accommodate a large number of simultaneous users also requires a large area. Reliability problems also exist because of the numerous mechanical components which must move during operation.
One developing technology for reducing these problems is to utilize what is known as a xe2x80x9cvideo server.xe2x80x9d The video and audio portions of the movie are digitized and stored as a stream of digital data in a mass storage system. When playback of the movie is desired, the digital data is accessed, converted back into an analog signal, and delivered to the user for viewing. Such a system is advantageous because one mass storage system can supply digital data representative of several movies to several users simultaneously. This can result in a lower overall cost per user. It can also result in enhanced reliability, due to the reduction in the amount of moving mechanical components.
VCRs, on the other hand, usually provided additional functions. VCRs typically can play the desired movie back at high speed, either in the forward direction (i.e., xe2x80x9cFast Forwardxe2x80x9d) or the reverse direction (i.e., xe2x80x9cFast Reversexe2x80x9d). They also can stop the playback of the movie before it has ended (i.e., xe2x80x9cStopxe2x80x9d). Many can also play the movie back at a slow speed (i.e., Slow) or freeze the movie on a particular frame (i.e., xe2x80x9cPausexe2x80x9d).
These VCR-type controls are useful and have come to be expected by users. Accordingly, it would be desirable to incorporate these VCR-type controls in a centralized video server system.
Playing back a movie at high speed, however, typically requires a much higher bandwidth in many of the components in the video server system, such as the mass storage system, the communication network, and the reception equipment. In many systems, this increased bandwidth is simply not available. In other systems, the cost of the increased bandwidth may be too great.
Another typical problem with playing back a movie at high speed is a marked reduction in the information which is communicated to the user. Typically, the audio is either completely eliminated or played back at a high-pitched and difficult-to-understand rate. The fast-moving video is also often confusing and unenjoyable. This problem, of course, exists even in connection with the traditional VCR machine.
One object of the present invention is to obviate these as well as other problems in the prior art.
A further object of the present invention is to provide VCR-type controls for a video server system.
A still further object of the present invention is to provide a video server system which can playback a desired movie at high speed, either in the forward or reverse direction.
A still further object of the present invention is to provide a video server system which can playback a desired movie at a high speed, without increasing the bandwidth requirements of the video server system.
A still further object of the present invention is to provide a video server system which can playback a movie at a high speed, but in a fashion that conveys a high degree of information and in a comfortable format to the viewer.
A still further object of the present invention is to provide a video server system which can deliver a movie at a high rate of speed which is stored in a compressed digital format, such as MPEG (xe2x80x9cMotion Picture Experts Groupxe2x80x9d).
A still further object of the present invention is to provide a video server system which can playback a movie at a high speed without significant additional cost.
These and still further objects, features and benefits of the present invention are achieved by playing back a sequential set of movie segments with an alternating series of intervening movie segments missing therefrom. Using this technique, the movie is effectively played back at a faster speed. But the speed at which any segment of the movie is played back is not increased. Such a system effectively plays back a movie at a high rate of speed, without increasing the required bandwidth of the system.
Such an approach is also believed to provide a high speed presentation which is more intelligible to the viewer and more comfortable for him to view.
Instead of no audio or high-pitched audio at a fast rate which is difficult-to-understand, the viewer hears audio at a normal pitch and rate. Although alternating segments of the audio are deleted, a series of chopped audio segments played back at normal pitch and speed are believed to be more intelligible and more comfortable to hear than a continuous audio segment played back at a high pitch and speed.
A similar advantage is believed to result in the video portion of the movie. The video which the user sees proceeds at its normal speed. Although alternating segments have again been omitted, segmented video at normal speed is again believed to be more intelligible and comfortable to view than continuous video at an accelerated speed.
In one preferred embodiment, each continuous segment which is played back is approximately two seconds in length. The alternating segments which are omitted are approximately equal in length to the alternating segments which are played back. This timing scheme is believed to be the most comfortable and comprehensible. It also results in a demand for data from the video server system which is most efficient using the video server system selected by Applicants.
Another feature of the present invention is directed to eliminating distortions which can occur in the beginning of each played back segment when playing back data stored in MPEG compressed format. The beginning of a played-back segment often may not coincide with the xe2x80x9cI-Framexe2x80x9d of a recorded MPEG stream, but rather with a xe2x80x9cB-Framexe2x80x9d or xe2x80x9cP-Framexe2x80x9d of that stream. As is well known in the art, I-Frames contain data representative of an entire movie frame, while B-Frames and P-Frames contain data representative of only changes that have occurred in a movie frame with respect to another movie frame. In one embodiment of the invention, the system ignores (i.e., drops), all initial B-Frames or P-Frames which are not preceded by an I-Frame. In an alternate embodiment, the system ensures that the reading of each played-back segment from storage begins with an I-frame.
These and still further objects, features and benefits of the present invention will now become clear from an examination of the drawings, taken in conjunction with the following detail description of the preferred embodiments.