Contemporary Research SignStream Media Express, Product Manual, Page: 23 / 24

Contemporary Research 23 SignStream Installation and Operation
Technical Specifications
If you’re working with a studio-based content provider, they may want a more complete statement on
preparation of the digital media files.
Minimum Encoding Requirements
TS File Multiplex Rate 19.392658 Mbps +/- 54 bps (ATSC)
TS clip start/end The TS file should begin and end on whole TS packet boundaries. The
file should begin with the TS sync byte (0x47) and contain an integer
number of TSpackets.
Minimum File Size 16 MB (6.6 secs @ 19.392658 Mbps)
Video Format One of 18 ATSC Formats (per ATSC A/53b)
Audio Encoding AC-3 (per ATSC A52)
PSI / PSIP MPEG-2 PSI (PAT and PMT) must be present in the multiplex. A static set
of ATSC PSIP tables should be present in the stream for some consumer
decoders that rely on PSIP information to acquire and tune to the
channel.
PID assignments in PAT, PMT, and TVCT service location descriptors
should be consistent file to file. TVCT should contain at least one valid
virtual channel definition.
Virtually Seamless Playlist Encoding Restrictions
The purpose of seamless mode restrictions is to create splice points at the beginning and end of each file that
adhere to the SMPTE-312M defined “seamless splice point” requirements. These specifications are in addition to
the requirements above.
Lead in/out black frames No restriction
Fade-in/out No restriction
Video Format 1080i, all files in a playlist. The encoded video format must be consistent
across all files to be spliced in a playlist.
Programs 1 Program containing 1 Video and 1 Audio service
Program PID assignments PMT PID: 16 (0x010)
PCR PID 17 (0x011)
Video PID: 17 (0x011)
Audio PID: 20 (0x014)
TS clip start The first GOP in the file MUST be CLOSED
TS clip end The file should not be padded with additional null packets.
VBV Encoding Method The VBV_delay at the beginning and end of every file must be the same
to ensure that the video buffer does not underflow or overflow at the
splice point.
This concept is identical to the SPMTE-312M restrictions on
“splice_delay”. This requirement can be achieved by using a constant
VBV_delay throughout all files, or by using an encoding algorithm that
forces VBV_Delay to a consistent value at the beginning and end of all
files.
VBV_delay can be examined as the delay between the access unit arrival
(in PCR time) and the actual stamped decoding time per DTS/PTS.