标准摘要
[中文适用范围]： 指定前导和预告片录制的最低要求，以帮助用户在开始录制节目材料之前调整设备以获得最佳性能。还指定之前的音频和视频信息 [外文原描述]： Specifies the minimum requirements for recordings on the leaders and trailers of video recordings to assist users to adjust equipment for optimum performance prior to the start of recorded programme material.
英文名称Audiovisual, video and television equipment and systems - Part 21: Video tape leader and trailer for education and training applications