Track Buffer

The size of the track buffer is left to the implementation, although the minimum recommended size is 2 Mbit. This is computed as: B > Tmax * VBRmax = 0.104 sec * 10.08 Mbit/sec

Tmax is the maximum latency of one disc revolution, and VBRmax is the maximum mux rate for any Program.

In some systems, the Track Buffer and the MPEG STD/VBV (System Target Decoder/Video Buffer Verifier) may be combined.

Seamless playback illustration

Input stream to Track Buffer:

  Time

  ---->           n: sector number   



                      |<------- T --------->|

  [n-3][n-2][n-1][  n]   ... track jump ...  [m  ][m+1][m+2][m+3][etc.]



                     (no data transfer during

                           discontinuity)








Corresponding output from Track Buffer:



    Initial buffer

    delay introduced by track buffer

  |<--------->|

               [n-3][n-2][n-1][  n][m  ][m+1][m+2][m+3][etc.]

                                  ^^

                                   no apparent discontinuity

                                   from perspective of MPEG Systems

                                   decoder.

The memory size needed for seamless playback control can be computed as:

T * VBR = 0.25 seconds * 8 Mbit/sec = 2 Mbits

This is of course implementation-dependent. T here is them maximum jump distance (10,000 sectors).