公开(公告)号：US5774497A

公开(公告)日：1998-06-30

申请号：US632036

申请日：1996-04-12

申请人： Simon A. Block ,  Trevor S. R. Dyck

发明人： Simon A. Block ,  Trevor S. R. Dyck

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, a local clock for generating timestamps and a display unit. The digital computer extracts from the data stream a PCR sample 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 line of best fit to a set of values including the PCR sample value and the timestamp, and previously received PCR sample values and associated timestamps. The line of best fit represents a reconstructed system time clock. The digital computer determines a PCR jitter value for the PCR sample value by determining a distance between the line of best fit and the PCR sample value. The PCR jitter value may be displayed on the 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，用于产生时间戳的本地时钟和显示单元。 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。 时间戳从本地时钟获得，并与PCR样本值相关联。 数字计算机确定与包括PCR样本值和时间戳以及先前接收的PCR样本值和相关联的时间戳的一组值最佳拟合的线。 最佳拟合线表示重构的系统时钟。 数字计算机通过确定最佳拟合线与PCR样本值之间的距离来确定PCR样本值的PCR抖动值。 PCR抖动值可以显示在显示单元上，优选地以直方图显示。