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Forum Home - Why the webcast looks blurry
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|10-18-2013, 11:26 PM||#1|
I pull your leg out!
Why the webcast looks blurry
One of the most frequently asked questions during the live webcasts we do here is "The video looks all blurry (pixelated, blocky etc.)" I will attempt to explain this phenomena the best that I can but keep in mind that I am a video production professional with a strong background in broadcast engineering so I am not that great at simple layman's terms explanations.
YouTube and the Powwows.com archives all look great so why does this happen to the live stream? Well it all has to do with how streaming live video works. When you are watching a video on a site like YouTube or Vimeo those videos are being streamed to you however unlike a live stream those videos were put through more exact and precise encoding and compression software that takes much longer to process but it yields a cleaner video with less compression and less blurriness. The other other advantage that videos from those sources have over a live stream is that they can be a much larger size (read as 'bit-rate').
With live streaming video there is a computer on-site that has to encode and upload the video to a CDN (Content Delivery Network), which a service that distributes the video to all the remote viewers (you). Since timing is critical and the video has to be uploaded in as close to real time to the server as possible the on-site computer is going to heavily compress the video into a stream that can fit within the limitations of the internet connect at the location. In some cases we have to generate several streams simultaneously to allow for slower connections or cell phones and tablets to view the video as well. With all of those streams generating and uploading at the same time the computer has to make the streams all fit on one internet connection that is shared with many many people and devices at the powwow.
To liken this to a familiar situation. Some of you may have a wireless router/modem in your house that you and your whole family use. Have you ever noticed that when everyone in your house is online that the internet seems to be running slower? Well the same thing above is what you are experiencing in your own house. It's all about traffic.
So why is it that sometimes the video appears clear during individual contests but it blurs when there are a lot of people or there is excessive fast motion? This has to do with the compression part of the stream. The way compression works in video is the computer looks at the video as groups of pictures (frames) and says to itself "what can I get rid of that isn't necessary?". Looking at Hunting Moon powwow the computer sees that there are sections that are not changing, like sections of the floor when no one is standing on it, the walls and the ceiling. Those items and anything else that doesn't change the computer throws out. Simply the computer keeps the first frame in each group fully in tact and then for the next several frames in that group it will only keep the information that has changed since the first frame. Now if you understood the stuff above you can see that when there are a lot of dancers out in the arena there is not so much that is static so the computer has to figure out how to fit all of the changing data into a video stream that can fit on the network. When the upload bandwidth (read as speed) is small or is just congested the computer again has to figure out the maximum size of each of the streams, and when it determines that the bit-rate needs to be small it will begin to toss out a lot more details.
Let me simplify that by relating it to an old technology. Cell-frame animation, the process that cartoonists used until the advent of computer animation - you know all the old Disney movies, Looney Toons, etc. Back in the day animators would save time by having a background artist draw the backgrounds and other elements that wouldn't need to be animated onto a solid piece of paper. The animators would then draw the characters and items that needed motion onto clear cellulose sheets and then stack them on top of the solid background and then snap a frame with the animation camera. They would then only change the sheets that had something change on them.
When you stream a video that isn't live you are also technically only downloading the video as a complete file whereas streaming the file is not complete.
OR it could be your internet connection or computer or both is slow and can't handle the video correctly.
If you need me to explain or elaborate anything more just post below.
CERN may have discovered the Higgs Boson but...
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|10-19-2013, 03:05 PM||#2|
Great post, thanks!
Adding that to our our page on webcast issues.
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