RFC 2448 (rfc2448) - Page 2 of 7
AT&T's Error Resilient Video Transmission Technique
Alternative Format: Original Text Document
RFC 2448 AT&T's Error Resilient November 1998
- using forward error correction (FEC) techniques
- transmitting HP segments over reserved channels or using
differentiated services.
Both redundant transmission and FEC techniques increase the bandwidth
needed to transmit the compressed video bitstream. FEC techniques
increase the effectiveness of this additional bandwidth for packet
loss protection at the expense of increased processing at the
receiver and the transmitter ends and increased overall delay. Using
channel reservations or differentiated services based approaches may
be the best solutions for protecting the HP segments but, they
require network infrastructure changes.
This document outlines another set of HP segment protection
techniques based on AT&T/Lucent patents [1, 2] that can be used for
reliable video transmission over packet networks without a built-in
prioritization mechanism. These techniques use reliable transport
protocols and "out-of-band" delivery approaches. In this context, the
term "out-of-band" is used to imply information transmission means
other than those used for transmitting the main video stream. The
details of these techniques are discussed in the following sections.
An implementation of these, as applied to MPEG-2 video transmission
over IP networks, is described in [4].
The IESG/IETF take no position regarding the validity or scope of any
intellectual property right or other rights that might be claimed to
pertain to the implementation or use of the technology, or the extent
to which any license under such rights might or might not be
available. See the IETF IPR web page at http://www.ietf.org/ipr.html
for any additional information that has been forwarded to the IETF.
2. Identification of the HP segments
The classification of a part of a video bitstream as an HP segment
depends on two factors. The first one is the encoding algorithm used
in compressing the video data. It is impossible to segment a
compressed video bitstream without knowing the syntax and the
semantics of the encoding algorithm. The second factor is the
determination of a compromise between the HP segment size and the
corresponding loss resilience. As the segment size increases, so does
the loss resilience. On the other hand, it may not be feasible to
deliver large HP segments reliably.
As an example, the "data partitioning" method of the MPEG-2 standard
[5] defines the syntax and semantics for one particular way of
partitioning an MPEG-2 encoded video bitstream into HP and LP
segments. In data partitioning, the smallest useful HP segment can
be selected to contain only the header information, which is usually
Civanlar, et. al. Informational