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.
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).