Digital Video Encoding
Video Streaming Protocols
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Digital Video Encoding
The Helios HD/SD cameras support four encoding modes providing up to two independent streams of digitally encoded video as listed below:
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•
•
•
H.264 Only
MJPEG Only
H.264 Stream 1 and MJPEG Stream 2
H.264 Stream 1 and H.264 Stream 2
(Not all of these modes are available on all of the Helios cameras. The HD camera video source produces progressive scan video and supports all four encoding modes. The SD camera produces interlaced video and only supports the last two dual streaming modes)
Video Transmission
TCP vs. UDP – At the Transport layer of the IP network stack, UDP (User Datagram Protocol) is the preferred method for the delivery of live video streams. UDP offers reduced latency over the reliability that TCP (Transmission Control Protocol) provides. It is a faster protocol than TCP and where timesensitive applications are involved (i.e. live video or VoIP), it is better to live with a video glitch caused by a dropped packet than to wait for the retransmission which TCP guarantees (which in not very practical where live video is concerned). However, as we will discuss later, TCP is definitely more firewall friendly as some networks will block UDP video.
UDP Video
Ideally, in a network where there is more than one client/viewer that wants to see a live video stream, you should use multicast video. Multicast video always uses UDP at the Transport layer. With encoded multicast video, the camera transmits only one instance of the video onto the network and the clients in turn grab a copy of the video from the network. Each client must first connect to the source camera to grab an SDP (Session Description Protocol) file which gives them the information needed to find the video on the network and begin decoding and rendering. With multicast video, CohuHD cameras listen for both RTSP (Real Time Streaming Protocol) and HTTP (Hypertext Transfer Protocol) as a means to
WHITE PAPER
Digital Video Encoding
The Helios HD/SD cameras support four encoding modes providing up to two independent streams of digitally encoded video as listed below:
•
•
•
•
H.264 Only
MJPEG Only
H.264 Stream 1 and MJPEG Stream 2
H.264 Stream 1 and H.264 Stream 2
(Not all of these modes are available on all of the Helios cameras. The HD camera video source produces progressive scan video and supports all four encoding modes. The SD camera produces interlaced video and only supports the last two dual streaming modes)
Video Transmission
TCP vs. UDP – At the Transport layer of the IP network stack, UDP (User Datagram Protocol) is the preferred method for the delivery of live video streams. UDP offers reduced latency over the reliability that TCP (Transmission Control Protocol) provides. It is a faster protocol than TCP and where timesensitive applications are involved (i.e. live video or VoIP), it is better to live with a video glitch caused by a dropped packet than to wait for the retransmission which TCP guarantees (which in not very practical where live video is concerned). However, as we will discuss later, TCP is definitely more firewall friendly as some networks will block UDP video.
UDP Video
Ideally, in a network where there is more than one client/viewer that wants to see a live video stream, you should use multicast video. Multicast video always uses UDP at the Transport layer. With encoded multicast video, the camera transmits only one instance of the video onto the network and the clients in turn grab a copy of the video from the network. Each client must first connect to the source camera to grab an SDP (Session Description Protocol) file which gives them the information needed to find the video on the network and begin decoding and rendering. With multicast video, CohuHD cameras listen for both RTSP (Real Time Streaming Protocol) and HTTP (Hypertext Transfer Protocol) as a means to