Abstract: A data recording and reproducing apparatus for recording and reproducing video signals in a plurality of formats with different rates to/from a record medium is disclosed. In the data recording and reproducing apparatus, a video signal in a selected format is converted into video data packets and audio data packets whose lengths are optimally designated corresponding to the selected format. With a video data packet and an audio data packet, a video sync block and an audio sync block whose lengths are different are formed, respectively. The video sync block and the audio sync block are encoded with respective error correction codes. The resultant data is recorded as record data to a record medium. Corresponding to the data rate of the video signal, at least one data packet is placed in one video sync block. A synchronization detecting apparatus automatically and accurately detects sync blocks with different lengths from a data sequence of record data reproduced from a record medium.