1. VOD
VOD (Video On Demand) video-on-demand technology is one of the new business hotspots launched on the network in recent years (originally originated in Japan, the central computer system directly transmits movies or video programs to the family's home according to the user's on-demand demand Entertainment system. In the future, video-on-demand is expected to enter other interactive TV services, including games, banking and personal finance, shopping and education services). Divided into TVOD (True VOD referred to as VOD) and NVOD (Near VOD) two ways. For each TVOD request, TVOD must output a corresponding video stream, which requires very large network bandwidth. NVOD can support on-demand requests from any number of users. Although the bandwidth problem is solved, each user may have to wait for a long time to get the corresponding service.
Three characteristics of TVOD:
1. Based on two-way network
2. Click and release
3. The number of concurrent streams is limited, the number of supported users is limited, and the cost per user is high
Second, NVOD
NVOD (Near Video On Demand) quasi-video on demand is one of the value-added services of the one-way digital TV system. It uses a video server to delay a digital TV program in several digital channels. The user can watch the program completely after waiting for a while while ordering the program.
Five characteristics of NVOD:
1.NVOD broadcast control system software features:
Graphical interface
Program scheduling uses an intuitive graphical interface to distinguish different playback states with different colors
Simple and clear operation
Support mouse drag and drop selection, support to add programs in batch, easy to add and delete
Automatic allocation of channel resources
The system can automatically calculate and allocate the number of channels according to the program length and program interval
Automatic detection of channel bandwidth
Separation of programming and broadcasting
For database operations. Program separation and broadcast separation can be achieved
Program upload function support
Program stream of local hard disk can be uploaded to video server
Print function support
Program schedule can be printed out, support print preview
Automatically calculate the sum of the program bandwidth of all digital channels at the same frequency point during the program scheduling process, if the maximum value is exceeded (38Mbps in QAM64), a prompt message will be given
2.NVOD program form generation software features:
Automatically extract data from the programming database to generate NVOD program forms
Use MPEG-2 Private Segment (Private secTIon) for package transmission
A single PID structure can be sent to the multiplexer for multiplexing output
The program list is dynamically refreshed as the program schedule changes
The TS stream is generated and output in memory, no files are generated, reducing the loss of the hard disk and increasing the TS stream generation speed
The program form data contains the system real-time clock information of the front-end server, which is used to synchronize the set-top box clock with the front-end clock
3.NVOD (Near VOD) transmission network: based on broadcast network
4.NVOD advantages: no number of users, low unit cost
5. NVOD disadvantages: long waiting time (10-15 minutes)
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