How to use video compression and choose the right video codec for uploading video to Youtube and other video sharing sites.
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In order to understand more about online video, we have to understand a little bit about video compression, which is what we’ll be looking at today on tips and tricks.
First things first, what is compression? Video compression is the quantification in bits of an analog video signal, essentially, how the light waves entering your lens end up as bits in your camcorder. The amount of compression and the math involved are generally set by the codec that your camcorder uses. Common video codecs are HDV, DV and AVCHD, and in most instances, this codec is also the one you edit your footage in. However, with online video, all of the above codecs are far too large and data intensive to stream over the internet, so we need to convert that video into another smaller codec to upload to an online distribution site. Once there, that site generally re-encodes your video into yet another codec that’s small enough to stream online. For example, we may shoot and edit video in the HDV codec, convert it to H.264 to upload to YouTube, who then converts it to flash video for distribution.
That’s a lot of compressing and recompressing and it wreak havoc on your images if you’re not careful. The key to avoiding the most damage to your video is to make sure that you are always moving from a higher codec to a lower one and never in reverse. A good rule of thumb is to notice the physical size of the next video codec you’re going into and make sure that it’s smaller than the previous one.
So, in our example above, we went from HDV to H.264, which was encoded by YouTube at 320 x 240, which should give you the best possible quality given the circumstances. You’re editing application should have multiple export options for changing video codecs. Most modern applications will already have some preset codecs available that are compatible with various online sharing sites. And there are even dedicated problems, such as Sorenson Squeeze, Adobe Media Encoder, and Apple’s Compressor, if you want a great deal of control over your settings.
Common formats for uploading are H.264, mpeg2, AVI and MOV. Once it gets to an online sharing site, the video is out of your hands and will most likely be compressed in Adobe’s Flash video format, as that is the codec that’s recognized by the vast majority of web browser’s out there. It can be a bit disheartening at first to see your beautiful HD video production squashed into a tiny web video window, but codecs are getting better and the internet speeds are growing. It won’t be too long before HD video transmission online becomes the norm rather than the exception. In the meantime, watch your compression to get the best image that you can possibly get.
The more that you understand about video compression, the more you can improve the overall quality of your online videos.
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