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Why does my video flicker?


Some (not all) of the time, when I attempt to watch a news clip or movie trailer online, the picture continually flickers. Why, and how do I fix it?

It depends on what you mean by flicker.

Various things can disrupt viewing video on-line. But the increase in popularity of
sites like YouTube and Google Video, in addition to the news and movie sites you mention,
has a lot of people giving it a try.

Let’s look at some of the issues.

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Let’s start with a definition: there are two ways to play video: streaming and
downloading. Both actually download the video to your computer, but it’s what happens
and when that makes the difference.

Streaming video, as its name implies, is viewed as it’s downloaded to your computer.
Typically the video player will buffer some amount of video – anywhere from a second or
two, to a minute or two depending on the length of the video, and then will start playing
as the video as soon as it can – well before the entire video is downloaded.

Downloadable video is exactly that – the video is first downloaded in its entirety,
and then viewed using a video player. In a sense it’s still “streamed” as you view it, but from your local
harddisk, rather than across the network.

One assumption made to support streaming video is that you can download the video
faster than it takes to watch it.
If your streaming video periodically halts, or the video stops but the audio continues, or
you get messages about “rebuffering” frequently, then your download speed isn’t fast enough to
keep up with the video.

“Download speed is perhaps the most common problem associated with viewing video

If your download speed can’t keep up, you have only two options, really: select a
different quality for the video, if you can, or download the video before viewing it.

Many video sites allow you to choose which of several versions of the video you
want to watch. The bigger, higher resolution video formats require a faster download
speed to stream without interruption. If you run into that problem, try choosing the
next lower quality video, if offered.

The other approach is to download the video. This isn’t always an option, since
it can enable content theft, but when available it works well. It doesn’t matter
that it might take an hour to download a five minute video because when you finally
watch it, it’s streaming off of your hard disk at top speed.

Download speed is perhaps the most common problem associated with viewing video

Other problems with video quality typically boil down to issues with your video
card, or the horsepower of the computer you’re using to view the video.

What confuses this issue is that different video formats place different demands
on the video card and CPU. So videos from one site using one technology may work
properly and look just fine, while videos from some other site might well have
issues such as flickering. Everything from the actual video card hardware, to its
drivers, to the version of DirectX that might be installed on your computer can
come into play. Even the computer itself can be an issue.

If you are having problems, one thing I would certainly try is simply updating
your video drivers and updating to the latest version of DirectX from Microsoft.
Generally staying up to date with Windows Update is also a good thing.

Your CPU plays a vital role depending once again on the video card and
video format. Video is compressed – meaning that in order to view it various
calculations have to be performed in real time as you view the video to decompress
it to a viewable form. “Various calculations” means math, and that means your
CPU has work to do. A slow CPU could certainly cause some types of videos not to render fast
enough for smooth viewing. Unfortunately, since the video card also plays such a big role in this, there’s
no hard and fast role as to how fast is fast enough.

If you have an older computer, or an older video card, it’s possible
that it’s simply not up to the task. Depending on your resources, upgrading
your video card could be the least expensive approach to the problem. Even
in older computers, newer cards do a good job of off-loading much of the work
from the CPU.

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6 comments on “Why does my video flicker?”

  1. If you’re running XP, you can bring up the Windows Task Manager which, among other things, puts an icon in the system tray to show the current CPU usage. Press Ctrl-Alt-Del to bring up the task manager, and then minimize the window. The system tray will have a little green crosshatch icon. As the CPU usage goes up, a light-green rectange will “grow” from the bottom of that icon. At 100% usage, the icon will be entirely filled.

    If, while playing the video, the CPU usage goes to 100% (all green), then that’s your answer — not enough horsepower on the system. (And, if the CPU usage isn’t near zero prior to starting the video, there may be other background tasks running that may not need to be.)

  2. its helpful but still confused when the website does not ask for the quality of the videos to be downloaded and still buffers when streaming on free video websites.

  3. Hi Leo, Can you pls tell how much download usage does watching online video incurs, ie, half-hour video?

    No. It varies widely, depending on the size, quality and encoding used on the video.

    – Leo

  4. Hello. I’ve always been able to watch online video without any problems until my conputer crashed, now it takes forever to watch video! I’ve run registry cleaners and virus scans, still have plenty of disc available as well as memory, etc…whats happened to my computer!!!

  5. Eh, the author clearly has no idea bout videos. Talking about streaming anddownload speeds is next to nonsense as at most it can cause video stalling, not flicker. Flickering most commonly occurs when an old movie has been digitised with a wrong framerate – e.g., a 30fps movie has been encoded in the 23.97 NTFS standard. This may cause video flickering – you need to delick (deflicker) the video.

    Most people I hear from use flicker to mean stuttering or stalling. Thanks for the vote of confidence.



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