Digital video has infiltrated our lives. Cable providers are selling digital video to compete with satellite providers, which have been promising better video and audio to consumers. DVDs are making inroads and bringing hours of high-quality video and audio to a disc the size of a CD. Enterprise customers, too, are finding uses for broadcast-quality video, whether for internal security or for broadcasting corporate meetings.
This technology has come down in price in the past few years. What used to be available only on ATM networks with large encoders can now be done by single chips on Ethernet networks for less than $5,000. That said, we wanted to know which devices could handle the biggest, busiest networks. We invited six companies to send us their best video encoders and decoders for testing in our Dallas labs. Of those, Amnis Systems (formerly Optivision), Cisco Systems, General DataComm (GDC), Minerva Networks and Optibase sent us units. Only 2netFX wasn't able to send equipment for our tests.
All the devices we tested encode audio and video, but there are differences on the transmission and decoding side. The equipment from GDC and Cisco supports transmission on ATM networks as well as Ethernet, while the other devices use only Ethernet as their transport medium.
Because video quality is subjective and MPEG is a standard, we opted to simulate the worst network and see how well the boxes handled it. Rather than look at the quality of the encoded video on a pure network, we set out to break the video stream. Using a DVD as our input source, we subjected the encoded video stream to latency, packet loss and reordered packets, and graded the units based on the quality of video we received on the decode side; all the units gave the same visual quality at the encode end. After all was said and done, Amnis' NAC 3000 Live Streaming Video Encoder and NAC 4000 Live Streaming Video Decoder/Receiver won our Editor's Choice award.
Although none of the units we tested handled loss very well, the NAC 4000 dealt beautifully with huge latency deviations as well as with reordered packets. No matter how much latency we dialed into our test gear, the video image stayed rock steady on the output side, never missing so much as one block of pixels. The Minerva VNP-201, with beta firmware, and the GDC MAC 500 tied for second place in video quality. Cisco, GDC and Optibase sent us units that can handle more than one video stream at a time, each offering the same quality as that of the single encoder/decoders we tested.
One additional note about the equipment we tested: Although the vendors use standards for encoding and compression, there are differences in how the data is encapsulated and transmitted over Ethernet frames. For this reason, the encoders and decoders are not interoperable.
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