User`s manual

User’s Manual v.13 QVidium
®
H.264 HD Video Codecs™
Copyright 2011-2013 QVidium
®
Technologies, Inc. Page 21 of 67
(1920x1080 resolution at 60 frames per second, Level A and Level B). You can change the
encoded output video resolution and frame rate using the corresponding parameters under the
Advanced Encoding tab. Without an HD encoding license, it will automatically scale am HD video
input to SD.
To produce the highest quality video with the least amount of bandwidth, storage space, and
lowest delay, you may choose to select H.264 encoding format, and select Capped VBR
streaming mode under the Advanced Encoding profile. However, since VBR mode can cause
problems with certain decoders, the encoder defaults to CBR mode.
As previously mentioned, along with CBR mode or VBR mode, we strongly suggest the use of
QVidium Packet Pacing (which is enabled by default) to smooth out the packet rate.
Note: If you require an accurate Stream Bit Rate, please check the bitrate in the Status page and
adjust the Stream Bit Rate as necessary, since the actual output bit rate may exceed the specified
value by several percent.
3.5 Configuring Packet Transport & Error Correction
The QVidium H.264 HD Video Codec™ features some of the most powerful and advanced error
correction capabilities found in any video over IP product. The QVidium H.264 HD Video Codec™
implements QVidium’s patented ARQ error correction and clock synchronization (US Patents
#7,551,647 and #7,522,528) for the more robust video transmission with the lowest delay.
QVidium’s ARQ (Automatic Retransmission Request) is a dynamically adjusting 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 QVPRO H.264 HD Video Codec™ minimizes network bandwidth and loading due to its
extremely efficient encoding and video transport. The HD Video Codec™ implements MPEG4-
AVC (H.264) High Profile (Levels 4 and 4.1) video encoding, providing advanced coding
techniques in hardware, such as CABAC processing, not normally found in other MPEG4 codecs.
Our codec also features variable bit rate (VBR) transport, which strips out unnecessary null
packets from the video transport stream to minimize network loading.
The QVPRO supports QVidium’s patented ARQ error correction. ARQ is a robust feedback-based
error correction that can successfully recover nearly all packet loss, even in harsh network
environments. However because of support for CBR, the QVPRO also supports SMPTE-2022
(ProMPEG) Forward Error Correction (FEC). Because the ProMPEG FEC specification does not
support VBR streams, you must use CBR mode when using ProMPEG FEC. However, as FEC
cannot anticipate varying network conditions nor correct many common forms of packet loss, for
the most effective error correction, we suggest using ARQ wherever possible.
In contrast with FEC, QVidium’s ARQ is 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.