What does it mean "stream"

H

hellboy80

Well-known member
I just read this great guide to HD formats (http://www.webvideoguys.com/Guide_to_HD.html) and I dont understand one thing - what does it mean "stream" in this context?
For example in this sentence "The throughput is so high you need specialized RAID storage and controllers in order to handle more then a single stream of it."
"single stream", "many streams" - what does it mean? maybe something like "single video track", "more video tracks"?
 
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Yes, in that context a "stream" is a live video & audio stream. Meaning it's a video playback signal that's running at full res and full frame rate with no dropouts or anything, so the video is "streaming" off the hard drive.
 
So when I'm editing project with one video/audio track, I'm editing "single stream" and when I'm editing project that has more video/audio tracks (multiply layers of video), I'm editing "more video streams", am I right?
 
Well, yes and no. In the context of the quote you gave, it depends on how many of those tracks are used simultaneously. For example -- if you're doing a picture-in-picture thing, then yes, you'd have two streams active, and would need hardware with adequate throughput to support two streams. But if you're doing largely one camera, and then cutting to another camera... then you don't have more than one stream active at any one time, so a single-stream-capable system would be enough. It doesn't matter which tracks you put the video on, all that matters is: how many video clips are you using simultaneously? A cross-dissolve needs two streams, obviously. Picture-in-picture requires at least two streams; if you're doing "The Brady Bunch" then you'd need at least nine streams!

The # of video tracks is only tangentially related to the number of streams. You could use forty tracks in your NLE, but as long as you never needed two different clips simultaneously, that could all be done on a single-stream system.
 
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