Telestream and Haivision Offer Encoding Best Practices
Video encoding is an art form for the streaming world, as publishers need to make sure their content looks as pristine as possible to the highest number of users. Helping publishers get up to speed on the latest encoding improvements were Kevin Louden, 产品经理 Telestream, and Tim Baldwin, vice president for the internet media division at Haivision, who took part in a StreamingMedia.com webinar last week entitled "Best Practices for Advanced Encoding and Transcoding."
Confused over the difference between x264 and H.264? Louden began his section of the webinar by explaining that x264 is an implementation of the H.264 spec, and not something separate. x264 is an open source implementation, one recently made available for commercial licensing. Telestream, Louden said, was one of the first companies to get a commercial license.
Diving into the basic principles of AVC (advanced video coding), Louden explained the bedrock principle that encoders gain in efficiency by recording changes in the video over time and space. The better an encoder is at determining changes, the better the results will be.
x264 is a better encoder, tests have shown, because it's able to look ahead. Louden explained that encoders break video frames into blocks, and look for blocks that are identical. The encoder can then reference one block for an identical block, becoming more efficient. x264 is able to look ahead in the video, looking at many frames for identical blocks.
Helping webinar participants with a different area, Haivision's Baldwin explained the benefits of live cloud transcoding. Baldwin began by defining terms: transcoding is when the end result video codec is different than the input codec; transrating is when the bitrates and resolution of the resulting video are different than those of the input video; and transmuxing is when the format (the container) for the codec is different than the format for the input video.
Publishers will want to look to the cloud for live encoding when they're in a place with limited uplink bandwidth, 鲍尔温说. Delivering five bitrates in two formats (RTMP and HLS) requires approximately 10Mbps of uplink bandwidth. For live events, that often isn't possible. With cloud encoding, the publisher uploads one high-quality stream. The cloud encoder then creates multiple versions which are passed along to the CDN for distribution.
Besides being constrained by bandwidth, publishers consider cloud encoding when their legacy equipment doesn't support today's dominant codecs (such as H.264/AAC) or todays dominant formats (such as RTMP, HLS, Silverlight, and, soon, MPEG DASH).
For more on x264 and live cloud encoding, watch the full webinar "Best Practices for Advanced Encoding and Transcoding." It will be archived online for the next 90 days.
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