The invention discloses a video and audio coding and decoding method and a device, which adopts double DSP principal and subordinate architectures. The principal DSP sends a code command to the subordinate DSP. Image data are collected from the subordinate DSP and are coded. A video bit stream is generated and is stored in a data postpositional memory zone, and a data receiving command is sent tothe principal DSP; the principal DSP polls the command of the subordinate DSP, and the video bit stream is read according to a data receiving command and is output through a net mouth after being packed; the principal DSP codes by collecting audio data, and an audio bit stream is generated and output through a net mouth after being packed; the principal DSP receives the video bit stream and the audio bit stream which are input from the net mouth and are synchronously processed after being decoded, and images and sounds are output. By adopting the technical proposal of the invention, full-duplex real-time video and audio coding and decoding can be realized and the requirements of bidirectional talkback and bidirectional visibility in video monitoring can be satisfied.