Abstract: A porous film is here disclosed which is obtainable by stretching a film in at least uniaxial direction, said film being formed from a resin composition containing 25 to 70 parts by weight of a polyolefin resin and 75 to 30 parts by weight of an inorganic filler; said resin composition further containing 0.5 to 10 parts by weight of dehydrated castor oil (a) and 0.01 to 5 parts by weight of hardened castor oil (b) based on the total 100 parts by weight of the polyolefin resin and the inorganic filler; and the amount of the component (a) being 20 to 95% by weight based on the total amount of the components (a) and (b). In this porous film, softness and feeling like cloth, moisture vapor transmission, uniformity of the film thickness and the like are equal to their conventional levels. Furthermore, the adhesive strength of a securing tape does not deteriorate because the third components (a) and (b) do not float on the surface of the porous film.

Abstract: A light reflective sheet is here disclosed which comprises a porous resin sheet and a protective layer laminated on at least one surface of the porous resin sheet; the porous resin sheet comprises a polyolefin resin and 100 to 300 parts by weight of a finely powdery inorganic filler with respect to 100 parts by weight of a polyolefin resin; the porous resin sheet is stretched at an area stretch magnification of 1.5 to 20 times; the light reflectance of the porous resin sheet at a wave length of 550 nm is 95% or more; and the stiffness of the light reflective sheet is at least 50 mm. A light reflector using the light reflective sheet is also disclosed. Preferably, the protective layer has a function as a UV light protective layer and/or a light leakage preventing auxiliary layer.

Abstract: In a magnetic tape on which digital picture data is recorded along helical tracks formed on the tape, the format used therefore is such that: each picture data segment consisting of picture data of one frame or one field is recorded in a plurality of consecutive tracks, the picture data segments are grouped into blocks, each block comprising a plurality of picture data segments, block numbers identifying the respective blocks are recorded in the tracks in the respective blocks, and picture numbers identifying the respective picture data segments within each block are written in the tracks which also record the picture data segments.

Abstract: In a digital video recording and playback apparatus, at the time of recording, an analog signal is converted into a digital signal by an analog/digital converter and the thus-converted digital signals are stored in a memory on the recording side for each unit such as a frame and a field under the control of a memory address controller on the recording side. The stored digital signals are recorded on a digital audio tape by a digital recording device. At the time of playback, the digital signals are played back from the digital audio tape by a digital playback device, and are stored in a memory on the playback side for each unit such as a frame and a field under the control of a memory address controller on the playback side. The stored digital signals are converted into analog signals by a digital/analog converter before being outputted.The read and write operations for each individual memory are different.