Compression encoding signaling (Compression, Encryption, Transmission)

The two main services companies in America using an MPEG-2 video compression , which is the one used to store movies on DVDs. With MPEG-2 compression , the provider can reduce the data size down to 5 270 Mbps or 10 Mbps ( depending on the format of the show ) is an important step that has made DBS service a success. With compressed digital data. Prototype satellite can transmit about 200 channels if uncompressed digital data. Satellite can transmit about 30 channels only. 

Broadcast Control Center Digital image data through access to high quality MPEG-2 encoder which converts items into an MPEG-2 video size and format of the information is correct for satellite receivers in your home .

The encoder analyzes each frame and agreed to encode it . Encoders to eliminate irrelevant information out. And to find the variable information from other frames to reduce the file size down . Each frame can be encoded using one of three methods: this method.

Encryption is an internal frame (Intraframe) contains a complete image for that frame . This encryption makes data compression is minimal.

Frame encoding a prophet (Predicted Frame) contain sufficient information to tell the satellite receiver how to display the following frame by frame or frames the basic data of forecasting , most of which were previously shown . This means that the frame illustrated with specific information on how the image changed from the previous frame .

Frame encoding a bidirectional (Bidirectional Fram) in the frame in two directions. Receiver must have the frame and the prediction frame encompassed . Using data from the closest surrounding frames . I will insert the receiver position and color for each pixel.This process can sometimes cause Arti fax (Artifacts) is a defect with some of the images shown on television. But for most of the images are clear and bright.

Size of data compression depends on the nature of the item. If the encoder is converting broadcast news. It can take a lot longer frames because most of the same scene from one frame to the next frame . In the other categories , such as movie length . And Music Video Things change very quickly from one frame to the next frame . Therefore the encoder must generate more internal frame . The result is that some items, such as news broadcasts typically compressed to a smaller size than the full length of the movie .

After the image is compressed Service providers need to be encrypted to prevent people from accessing information without paying. Encoding will distort (Scramble) digital data to make it unreadable . That way they only have to decrypt the data only . ( Converted back into usable data ) if the receiver has decoded the correct sequence and combination lock.

When the signal is compressed and encrypted. Broadcast center sends a signal to the satellites one. Satellite receiver is using a satellite dish on . Amplifiers and use another plate to signal back to Earth , where viewers can not receive.