公开(公告)号：US5883924A

公开(公告)日：1999-03-16

申请号：US878423

申请日：1997-06-18

申请人： Michael Yiu-Kwan Siu ,  Trevor S. R. Dyck ,  Simon Alexander Block ,  Chong T Ong

发明人： Michael Yiu-Kwan Siu ,  Trevor S. R. Dyck ,  Simon Alexander Block ,  Chong T Ong

IPC分类号： H04L29/14 ,  H04N17/00 ,  H03B3/46

CPC分类号： H04N17/004

摘要： A method and a test instrument are provided for measuring program clock reference (PCR) jitter in a data stream, such as an MPEG-2 transport stream. The test instrument includes a line interface circuit for receiving the data stream, a digital computer for processing the data stream and a local clock for generating timestamps. The digital computer extracts from the data stream a PCR sample value which represents a count of a system time clock used to generate the data stream. The timestamp is obtained from the local clock and is associated with the PCR sample value. The digital computer determines a reconstructed system time clock from a set of values including the PCR sample value and the timestamp, and previously-received PCR sample values and associated timestamps within a window representative of a predetermined time interval. The window is shifted as new PCR sample values are received. The digital computer determines a PCR jitter value for the PCR sample value by determining a deviation of the PCR sample value from the reconstructed system time clock. The PCR jitter value may be displayed on a display unit, preferably in a histogram.

摘要翻译： 提供了一种用于测量诸如MPEG-2传输流之类的数据流中的程序时钟参考（PCR）抖动的方法和测试仪器。 测试仪器包括用于接收数据流的线路接口电路，用于处理数据流的数字计算机和用于产生时间戳的本地时钟。 数字计算机从数据流中提取表示用于生成数据流的系统时钟的计数的PCR样本值。 时间戳从本地时钟获得，并与PCR样本值相关联。 数字计算机从代表预定时间间隔的窗口中的一组值确定重构的系统时钟，以及先前接收到的PCR样本值和相关联的时间戳。 当接收到新的PCR样本值时，窗口移动。 数字计算机通过确定PCR样本值与重构的系统时钟的偏差来确定PCR样本值的PCR抖动值。 PCR抖动值可以显示在显示单元上，优选地在直方图中显示。