Frame composition and function description of video conference terminal
1. Video codec: encodes and sends video from a video source (such as a video camera), decodes the received video code, and outputs it to a video display device (such as a television).
2. Audio Codec: Encodes and sends audio signals from an audio source (such as a microphone), decodes the received audio code, and outputs it to an audio output device (such as an audio speaker).
3. Data Channels: Supports telematics applications such as electronic whiteboards, still image transfer, file exchange, database access, audio graphics conferencing, and more. The standard data application for the Audio Graphics conference is the T.120 standard.
4. System Control Unit: Provides signaling for proper operation of H.323 terminals. It provides call control, capability exchange, signalling of commands and indications, and messages.
5. Receive path delay: To maintain synchronization with other media on the receive processing path, the media stream can be delayed. For network delays (causing packet arrival jitter), media streams can also be delayed.
4. System Control Unit: Provides signaling for proper operation of H.323 terminals. It provides call control, capability exchange, signalling of commands and indications, and messages.
5. Receive path delay: To maintain synchronization with other media on the receive processing path, the media stream can be delayed. For network delays (causing packet arrival jitter), media streams can also be delayed.
6. H.225.0 layer: Format the sent video, audio, data, and control streams to form a message output to the network interface. At the same time, extract the video, audio, data, and control streams from the messages received from the network interface.
7. Packet network interface: The encapsulated data stream is converted into a code stream that can be transmitted on various transmission networks and is transmitted to the network for transmission.