Patent ID: 7817765

Claim:
In a digital transmission apparatus for storing an input stream in a memory at a writing speed, the input stream comprising a packet train including a packet to which time information representative of a time reference is set, and for reading out an output stream from said memory at a reading speed higher than the writing speed, the digital transmission apparatus, comprising: first detection means for generating a first detection signal when detecting the time information in the input stream; oscillation means for oscillating a local clock signal having a frequency of a reference clock for the input stream; a counter for counting the local clock signal from said oscillation means; first latch means for latching the counted value of said counter in response to the first detection signal; first exchange means for subtracting the counted value latched by said first latch means from the time information in the input stream and applying an input stream having the subtracted result as new time information to said memory; dummy insertion means for inserting a dummy packet into the output stream from said memory when a difference between the reading speed and the writing speed exceeds an allowable range; second detection means for generating a second detection signal when detecting the time information in the output stream from said dummy insertion means; second latch means for latching the counted value of said counter in response to the second detection signal; and second exchange means for adding the counted value latched by said second latch to the time information in the output stream from said dummy insertion means and generating an output stream having the added result as new time information.