Atsc working Draft Template

dcc_end_time
– This field shall specify the nominal endpoint of the time interval during which the 
DCC request shall be in effect, expressed as the number of GPS seconds since 00:00:00 UTC, 
January 6, 1980. The optimum switch point for the end of a Temporary Retune DCC event is 
indicated by 
splicing_point_flag
and 
splice_countdown
fields. The optimum switch point for the video 
ES shall be indicated by its 
splicing_point_flag
and 
splice_countdown
fields. The optimum switch 
50 

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ATSC A/65:2013 
Program and System Information Protocol 
7 August 2013 
point for each audio ES should be indicated by its 
splicing_point_flag
and 
splice_countdown
fields. 
The optimum switch point for all other Elementary Streams that are elements of the program 
may be indicated by their 
splicing_point_flag
and 
splice_countdown
fields. 
The 
splicing_point_flag
and 
splice_countdown
fields shall be carried in the adaptation fields of the 
TS packets carrying the Elementary Streams, as defined in Sections 2.4.3.4 and 2.4.3.5 of MPEG-
2 Systems [13]. The first TS packet transmitted containing splice point information for each 
Elementary Stream for a given DCC request shall indicate a 
splice_countdown
value of not less than 
5. The channel change should nominally occur when the DCCRR’s internal time of day clock (as 
synchronized with the System Time Table received on the same Transport Stream) reaches 
dcc_end_time
, but the DCCRR should use the 
splicing_point_flag
and 
splice_countdown
fields to effect the 
timing of the switchover. The switch point timing as signaled by the MPEG-2 
splicing_point_flag
if 
present shall be within one second (plus or minus) of the time indicated in 
dcc_end_time
. If a splice 
point is not detected in an ES within one second following the 
dcc_end_time
and a splice countdown 
is not in progress, the DCCRR shall perform the elementary stream switch without further delay. 
If a splice countdown is in progress in the ES, the DCCRR should perform the Elementary Stream 
switch at the splice point.