QVidium MPEG2+4 Codec


Decoder: Explanation of Settings and Operation

 

Decoding Parameters

This section covers parameters related to decoding settings.

 

Stream Type: This allows selection between Transport Streams and Program Streams. Generally Transport Streams should be selected, but for bitrates under 1 Mbps, the Program Stream type works better. Program Streams allow variable bitrate encoding for better quality at low bitrates.

 

Video Encoding: The MPEG2+4 Codec generates analog composite and S-Video outputs from a video/IP packet stream encoded using either the MPEG-2 video encoding standard (MP@ML) or MPEG-4 simple profile ( ISO/IEC 14496-2) compression, as selected.

 

Video Format: This allows selection between the NTSC standard as used in North America and Japan and the PAL video format used in Europe for the analog output video signal. NTSC generates interlaced video at 29.97 frames per second, while PAL generates interlaced video at 25 frames per second.

 

Notification Parameters

This section covers parameters related to settings for sender notification parameters.

 

Notify Sender: This enables or disables notification messages to the sender.

 

IP Address: This is the IP address of the sender that will receive the notification. Currently the notification messages report to the sender the IP address of the receiver. This is done so that when DHCP is enabled on the receiver, the sender will be informed of the receivers IP Address. This notification occurs when the receiver is turned on.

 

Password: This is the System Password on the Sender. If the sender does not have a system password, leave this field blank.

 

Network Parameters

The fields below relate to Ethernet/IP video transport settings.

 

IP Transport: This selects the type of video IP packet decapsulation and error correction expected by the codec in receiving a Video/IP stream. All packetized video transport mechanisms expect to receive a multiplexed constant bit rate MPEG-2 transport stream to decapsulate and decode.

 

 

Multicast Address: This specifies the IP multicast address, if any, to listen to for the Video/IP stream. If expecting a unicast video/IP stream, leave this field blank.

 

UDP Port: This specifies which UDP port number (base 10) to listen on for the Video/IP stream.

 

Jitter: Packets in incoming IP packet streams may lose their ordering or suffer variable delays during transport through an IP network. The QVidium MPEG2+4 IP Codec buffers all incoming video/IP packets in a buffer and reorders RTP encapsulated packets by RTP sequence number. This parameter specifies the size of this incoming packet buffer in milliseconds of delay. Specify 0 here to disable this additional buffering when latency needs to be minimize.

 

ARQ Parameters

The parameters below ONLY pertain to QVidium ARQ error correction. They will be ignored unless ARQ is selected for IP Transport.

 

ARQ Port: This sets the UDP port that ARQ error correction uses to send upstream retransmission requests to the encoder. If you have a firewall, make certain that it allows outgoing packets on this port. On the encoder side, please make certain that the remote firewall will allow these requests in. This setting MUST match the corresponding setting on the encoder side.

 

Mode: This sets the whether to use Manual Mode or Auto Mode for ARQ. In most instances Auto mode should be selected.

ARQ Manual Mode Parameters

The parameters below ONLY pertain to QVidium ARQ error correction when in Manual Mode. In most instances you should not use this mode.

 

Number Retries: This sets the number of times a missing packet is requested. Usually 2 times is sufficient.

 

Round Trip Time: This sets the time to wait before requesting a missing packet again.

ARQ Auto Mode Parameters

The parameters below ONLY pertain to QVidium ARQ error correction when in Auto Mode.

 

Target Latency: QVidium’s ARQ error correction operates through the addition of a small additional buffering delay to provide enough time to request and receive replacement for each lost packet. Target Latency gives the ARQ mechanism a target value for determining the necessary ARQ delay. The ARQ divides the Target Latency, specified in milliseconds, by the round-trip time to the video encoding source to determine the number of request attempts. Unless Robust Mode is enabled, it sets a minimum ARQ latency of one round-trip time. A larger Target Latency allows the system to increase the number or repeat requests.

 

Max Burst Drop: Burst packet losses are common occurrences in many IP networks and the Internet. IP networks may dynamically change paths in response to load balancing, link failure avoidance, and for other reasons. During a re-route, a sequence of queued packets on a discontinued path may be dropped. A burst of packets may be dropped when higher priority packets stall a lower priority buffer. ARQ will notice a burst packet loss when the first packet after the loss arrives at the codec. Setting the Max Burst Drop Delay (in milliseconds) will delay the ARQ repeat request by this amount to handle packet burst losses.

 

Robust Mode: Normally, the ARQ will only require that a minimum of one repeat request is sent to the video encoding source device, regardless of the Target Latency. However, enabling Robust Mode will increase the minimum number of repeat requests to a minimum of two retries.