User Manual v.2
QVidium
®
QVENC4K™ UHD/HEVC Video Encoder
Copyright 2023 QVidium
®
Technologies, Inc.
Page 24 of 43
2.3 QVidium ARQ Video Transport & Error Correction
The QVidium QVENC4K Video Encoder
™ features some of the most powerful and advanced error
correction capabilities found in any video over IP product. The QVENC4K implements QVidium
’s
patented ARQ error correction and clock synchronization (US Patents #7,551,647 and #7,522,528)
for robust video transmission with the lowest delay
. QVidium’s ARQ (Automatic Retransmission
Request) is a dynamically responsive feedback error correction mechanism designed specifically
to enable the highest quality video transport over wireless networks and the Internet. ARQ senses
packet loss at the receiver and requests replacement packets from the server. ARQ can provide
nearly flawless reproduction of a video stream even through extremely lossy or congested
networks.
The QVENC4K HEVC UHD Video encoder minimizes network bandwidth and loading due to the
high efficiency of HEVC encoding and ARQ video transport. The QVENC4K
™ implements HEVC
(H.265) Main Profile video encoding, providing advanced coding techniques in hardware.
The QVENC4K
supports QVidium’s patented ARQ error correction as well as new industry
standard RIST and SRT protocols for interoperability with third-party encoders and decoders. ARQ
is a robust feedback-based error correction that can successfully recover nearly all packet loss,
even in harsh network environments.
In contrast with Forward Error Correction (FEC), ARQ employs a feedback mechanism that detects
packet loss at the receiver and requests the retransmission of only those lost packets from a video
source. A user-configurable buffer at the receiver (decoder) delays the video stream just long
enough to allow the system to replace any missing packets and re-insert them in their proper order
without disturbing play out of the video stream. Because ARQ senses actual packet loss, rather
than attempt to predict packet loss, it can precisely and completely restore all lost packets without
disturbing timing of the video play out. In contrast to FEC, ARQ can successfully recover lost
packets regardless of the magnitude or pattern of the packet losses, provided that the network
connection has enough capacity to send both the original video stream and the replacement
packets.
ARQ shares similarities with robust packet transport protocols, such as TCP/IP in that both use
feedback to create robust network packet transport. However TCP/IP uses a sliding window that
limits the number of packets that a source can have in transit and requires a positive
acknowledgement for each window of packets.
This limits TCP’s throughput, especially over links
with long latencies. Furthermore, under heavy loss conditions, TCP/IP scales back the data
transmission rates and provides no concise deadlines or constraints on packet delivery times. For
real-time video, this limits the usefulness of TCP/IP, making it unacceptable for low-latency uses.
In contrast with TCP/IP, QVidium designed its patented ARQ error correction specifically for live,
interactive, real-time video and audio signals to automatically recover nearly all lost packets with
minimal latency and over nearly any link loss conditions. It adds a small configurable amount of
delay to the network transport in exchange for significantly improving the robustness and reliability
of video transport.
2.3.1 Configuring Video over IP Network Parameters
To configure the IP network parameters, within the Network Parameters section of the encoder
profile, first select an IP Transport mode. Depending upon the IP Transport more that you select,
tables of additional optional parameters relevant to that IP Transport will then appear. For more
protocols, you will also be required to specify the destination IP address and UDP port number.
The destination IP address is usually a unicast IP address, but for UDP and RIST Simple Profile, it
can also be a multicast address.
For QVidium ARQ, you may specify up to 4 comma-separated destination IP addresses for