Abstract: [Problem] When a beam is emitted from inside a pipe onto an inside surface of the pipe using an ultrasonic probe in which flat plate-like transducers are arranged, since the transduces are in the shape of flat shape, signals reflected from the tubular pipe wall do not always return straight to the transducers, and scattering and interferences occurs in the returning waves.

Abstract: A video data recording/reproducing apparatus is designed to effect the high density recording for low bit rate coded data, correct the error with high reliability and reproduce only the main signal. For this purpose, an error correction circuit corrects the error in a transmission path by use of a parity code added by a parity adding circuit on the transmission side. A switch selects one of outputs of the parity adding circuit and error correction circuit according to whether the parity code is contained in the transmission data or not. A recording/reproducing circuit causes an output of the switch to be recorded. At the time of reproducing operation, the error correction circuit corrects the error in the recording/reproducing operation by use of the parity code contained in the reproduced signal.