-Video compression refers to reducing the quantity of data used to represent video images and is a straight forward combination of image compression and motion compensation -There are no magic settings that fit all projects. Major factors that dictate the need and amount of compression depend on your delivery method and your audiences connection speed and hardware. As well the content within the video has a major factor on compression settings.
. Video compression, like data compression, is a tradeoff between disk space, video quality and the cost of hardware required to decompress the video in a reasonable time. However, if the video is over compressed in a lossy manner, visible (and sometimes distracting) artifacts can appear.
Similarities can thus be encoded by merely registering differences within a frame (spatial) and/or between frames (temporal). Spatial encoding is performed by taking advantage of the fact that the human eye is unable to distinguish small differences in color as easily as it can changes in brightness and so very similar areas of color can be &quot;averaged out. With temporal compression only the changes from one frame to the next are encoded as often a large number of the pixels will be the same on a series of frames. Interframe compression uses one or more earlier or later frames in a sequence to compress the current frame, while intraframe compression uses only the current frame, which is effectively image compression
There is no simple answer to these settings unfortanityly. Different video requires different styles of compresion. There is always a trade off of somekind. Depending on your audience may change your technique
NTSC was designed to utilize the limited bandwidth into homes for broadcast video, this standard was developed around 1950 and slightly modified for color in the 1960’s. This standard will cease to be used in Feb 2009 due to advancements in Digital video. Interlaced shows odd lines then even lines sequentially and human eyes combine the two fields into one image. @ 29.97 Progressive scan takes more bandwidth, every frame is shown in it’s entirety which is closer to film in nature. All video should be de-interlaced before compressing. The reason being is when you lower frame rates on the video Interlaced images will show artifacts
This should be an example of Compressing but leaving it interlaced
I n telecommunications and computing, data rate is the number of bits that are conveyed or processed per unit of time. The bit rate is quantified using the 'bits per second’ ‘kilobites per second’
Make the size of the video smaller to compensate and gain some quality If video won’t play smoothly maybe data rate is too high.
This example is keyframe every 5 frames
Adjusting by halfs because of the complexities involved with figuring out which frames to drop
Size the video is going to be on the screen not the size of the file.
Most video compression is lossy, i.e. it operates on the premise that much of the data present before compression is not necessary.
For example, DVDs use a video coding standard called MPEG-2 that can compress ~2 hours of video data by 15 to 30 times while still producing a picture quality that is generally considered high quality for standard-definition video
Video Compression is a trade off between video quality, disk space, and hardware needed for decompression
Data rate greatly impacts quality of the video as well as size. I usually start with the automatic settings built into most current programs. Rule of thumb 300kbs for med-high bandwidth streaming 100kbs for dial up.
-Some computers cannot handle higher data rates
-Think about how your audience will retrieve your video and let the software do the work