The invention provides an AV (audio/video) encoding and decoding device, comprising a decoding module, a playing module, a conversion control module and an encoding module. The decoding module is used for importing a media file and calling a corresponding decoder to decode the media file, and the playing module is used for playing decoded AV data. The conversion control module is used for carrying out relevant processing on the decoded AV data, including the processing of scaling and effect adding on video resolution ratio according to encoding parameters, the processing of frame repeating and losing according to the frame rate and the time stamp, the processing of sampling rate conversion on audio data, the processing of discarding or silencing data filling on the audio data according tothe data volume and the time stamp, and the processing of connecting a plurality of media files into one. The encoding module is used for calling a corresponding encoder and a media file synthesizer to generate a multimedia file in the specified format and with relevant parameters. The invention lowers the dependence of a user system environment, and leads software to be controllable in quality and have strong maintainability.