QVidium QVMP2C-1011 User Manual

Page 36

User’s Manual v.28

QVidium™ MPEG2+4 Codec

ProMPEG FEC

The parameters below ONLY pertain to ProMPEG forward error correction. They will be
ignored when ProMPEG IP Transport is not selected.

Columns: This sets the number of columns in the two-dimensional packet interleave
matrix used by ProMPEG Release 3 FEC to generate column parity checksum packets.
The larger this number, the larger a contiguous burst packet drop that the FEC can
handle will be. However, increasing the number of columns increases the transport
latency. Column packets are sent on port P+2 (default: 10002).

Rows: This sets the number of rows, R, in the two-dimensional packet interleave matrix. It
thereby sets the FEC overhead, since one FEC packet is generated for each R rows. Thus,
column-only FEC will add an additional 100/R percent to the baseline transport stream
bit rate without FEC. Row parity is sent on port P+4 (default: 10004).

In ProMPEG Release 3.2 FEC, a row parity packet can be generated along each row of
the interleave matrix. Thus for a matrix having C columns, one row parity packet would be
generated for each C columns. This can add an additional 100/C percent overhead to the
transport stream bit rate for when enabled. However, these row checksum packets will
NOT be generated UNLESS “FEC Type” (below) is "Row and Column" FEC.

FEC Type: This allows selection between "Column Only" FEC and "Row and Column"
FEC. Normally, FEC without row parity can be effective in reconstructing isolated single
and burst packet losses. However, should the packet loss patterns become more frequent
and occur at intervals less than the total (row x column) number of packets held in the
interleave array, then column-only FEC will not be completely effective in recovering lost
packets. The addition of row FEC increases the ability to recover lost packets when the
losses start to occur in shorter intervals.

ARQ

The parameters below ONLY pertain to ARQ error correction. They will be ignored when
ARQ IP Transport is not selected.

ARQ Port: By default, ARQ normally sends upstream retransmission request packets on
UDP port 7020. You can change this ARQ Port setting to any valid and non-conflicting
UDP port. However, you must make certain that you specify the same port number at both
the encoder and the decoder.

This manual is related to the following products:

QVSDI-11-IP