Abstract: A DVD-RAM disk reproduction apparatus for reducing an error during detection of ID data, which includes a first operational amplifier for obtaining a sum signal resulting from the addition of four picked-up signals picked up by divided-by-four photodiodes from a DVD-RAM disk having a header region and a recording region, second and third operational amplifiers for respectively obtaining two sum signals corresponding to the upper and lower regions of the header region resulting from the addition of the first and second picked-up signals and the third and fourth picked-up signals, respectively, a fourth operational amplifier for obtaining a difference signal between the two sum signals, a header region detector for detecting upper and lower header region signals corresponding to the upper header region and the lower header region based on the difference signal, and detecting a header region signal corresponding to a header region by logically summing the two detected signals, a first multiplexer for selecting o

Abstract: A rotary head drum having at least one stabilizer installed in a magnetic tape recording and/or reproducing apparatus is described, in which at least one stabilizer is provided to bring about the stability of the traveling of a tape which travels while in contact with the circumferential surface of a drum. The stabilizer has a circular plane of a predetermined diameter, and the circular plane is mounted in a lower fixed drum to be partially in contact with the tape, thereby rotating with the tape at the same linear velocity. The tape only slightly vibrates while traveling in contact with the stabilizer, and travels with stability. Noise due to jitter, wow and flutter caused by the tape vibration is eliminated in the picture and sound. This rotary head drum is utilized in a video cassette recorder, digital audio tape recorder, etc.