DekTec DTC-300 StreamXpress - Manual (Page 65)

DTC-300-SP – StreamXpress
USER MANUAL
65
#6 Number of TS packets per IP :
This field allow the selection of the number of TS packets per Ethernet packets (1 to 7). The standard
size of an Ethernet packet is 1500 bytes. With the Ethernet, IP, UDP and RTP header, there is 1446
Bytes available for data. As each TS packet is 188bytes, the maximum number of TS packets that an
Ethernet frame can carry at once is 7x188 packets. Less packets can be encapsulated into an
Ethernet packet (1 to 7) but 7 is the most common and efficient way of encapsulating MPEG-2 TS.
#7 FEC :
If the Ethernet link is lossy, it may be useful to use FEC in order to improve the quality of the delivery
by adding redundant information to the main TSoIP streaming.
The FEC scheme for DVB-IP is defined in SMPTE 2022. FEC works by sending extra packets of
information along with the original payload. The FEC packets can be used at the receive end to
recreate data packets that have been lost during transport. The amount of data that can be
recovered is directly related to the amount of FEC data sent. There are 2 dimensions for the
SMPTE2022: Row and Columns.
The Column FEC stream is sent with the same destination IP address but the port in incremented by
2 from the main TSoIP port.
The Row FEC stream is sent with the same destination IP address but the port in incremented by 4
from the main TSoIP port.
Depending on the combination of Rows and Columns, more or less lost IP packets can be
recovered.
D represents the number of Row and L the number of Columns.
3.7 Playing an SDI (.dtsdi) file though a SDI interface
The StreamXpress supports the playout of uncompressed SDI video over interfaces supporting SDI
playout.
The format of the recorded SDI files supported by the StreamXpress is proprietary and is called dtsdi
format. Dtsdi files are created using DtGrabber+ recording applications or DtRecord utility.
There are 2 sub formats for dtsdi files: Huffman compressed and no compression. Using Huffman
compression for recording is recommended as it limits the required PCI bus bandwidth. The
StreamXpress will detect and recognized automatically if a file is Huffman encoded or not.
NOTE: For USB-2 device like DTU-205 or DTU-245, Huffman encoded files MUST be used as the
USB-2 bandwidth cannot handle uncompressed SDI files in most cases.