Video Compression

General Considerations

• Recompressing video leads to quality degradation, such as artifacts. Use raw footage or the least compressed footage that is available to you.
• Make the video as short as possible.
  • Trim the beginning and end
  • edit the video to remove unnecessary content.
  • use titles to fill in missing content or shift scene
• Adjust compression settings.
  • Each video has varying attributes that affect compression and file size
  • test the results and modify the settings.
• Limit effects and rapid movement
  • movement, particularly with many colors, increases file size.
  • Shaky camera work & zooms increase file size.
  • Some effects add information to the video &increase file size
  • some effects, such as blurs, decrease the number of bits in a compressed file & decrease file size.
• Choose appropriate dimensions.
  • If target audience has a slow Internet connection (such as dialup), make the dimensions of your video smaller --160x120 pixels.
  • If audience has fast connections, make dimensions larger --320x240 pixels.
• Choose appropriate frames per second (fps).
  • If target users have older computer processors, choose a low rate of frames per second (such as 7 or 15 fps).
  • If target users have newer computers, use a higher rate of frames per second (such as 15 or 30 fps).
  • Always choose an fps that is a multiple of the original frame rate: usually 7.5, 15, 30 fps.
• Choose appropriate number of keyframes.
  • Video keyframes differ from keyframes in Flash.
  • Each keyframe is a frame that redraws when the video is compressed
  • the more frequent your keyframes the better the quality.
  • More keyframes also mean larger file size.
  • If you choose 15 kps, the quality is higher because a keyframe draws ever 15 frames and the pixels in your footage are more accurate to the original.
• Reduce noise.
  • Noise (scattered pixels in footage) increases file size.
  • Reduce noise in Premiere to reduce video file size.
  • Using more solid colors reduces its file size.
  • use Video Noise Reduction filter in the Adobe Media Encoder,
  • Use soft blur in After Effects to help reduce noise

About exporting for the web

• web accommodates a wider variety of video and audio standards and devices.
• While a growing number of viewers have a broadband Internet others use equipment that supports only low data rates and, therefore, lower‑quality content.
• Therefore, export your project in a variety of formats, each tailored to different audience viewing capabilities.
• Premiere and After Effects export settings contain presets for many bandwidth scenarios that match output files for viewing requirements for theaudience.

Types of web delivery

• web standards for delivering video and audio content are varied and inconsistent.
• Audiences view content over the web using a variety of software and hardware configurations that support a wide range of data bandwidths.
• Therefore, numerous codecs designed to make video web‑friendly.
• Premiere includes presets to aid in formatting a movie suited for particular audiences, according to their system’s capabilities.
• Many formats employ the following technologies

Progressive downloadable video

• A progressive downloaded video begins playing before it is completely downloaded.
• The movie player software (QuickTime Player, Windows Media Player, or Real Player) calculates how long it will take to download the entire movie
• It then begins playback once enough of the movie has been downloaded so that it can play back uninterrupted.

Streaming video

• Streaming media delivers video over the web or other network without downloading a file to a hard disk, comparable to the way a traditional broadcast works.
• The bitrate (quality) of streaming video is constrained by the bandwidth of the network or modem.
• When streaming video over the web, specify a higher bitrate if audience has broadband Internet access-DSL or cable.
• use encoder’s Audiences or Alternates feature to provide versions tailored to the bitrate limits of different viewing scenarios.
• Streaming video is most effective over an intranet, with a high‑speed consistent bandwidth.
• Flash Video, QuickTime, Windows Media, and RealMedia include streaming media formats