Applying time compression to your content

By applying time compression to your content while it is encoding, you can speed up or slow down the content during playback. Speeding up the content reduces the amount of time required to view the entire video or listen to the entire audio file, which is useful when you have to fit content into a specific time slot. Slowing down the content can improve comprehension in situations where the material is highly technical or the language is not native to users. Using time compression has the following requirements:

• Your source must include audio content.
• Every source in the session must be a file.
• You must encode to a file. (Time compression is not supported for broadcasts.)
• You must be using a one-pass encoding mode (either one-pass CBR or quality-based VBR).
• You cannot apply the inverse telecine filter in conjunction with time compression.
• You cannot use the looping feature in conjunction with time compression.
• You cannot apply time compression when sourcing from multichannel audio.

If you are sourcing audio and video from separate files, encoding will stop when the end of the file with the shorter duration is reached.

Windows Media Encoder has two time compression features that you can use independently of one another or in tandem:

• Accelerating or decelerating the audio and video frames. Accelerating and decelerating have no effect on the pitch of the audio stream.
• Detecting and removing pauses in voice or action. Periods of silence are removed from the audio, and frames are removed from the video. If you elect to create a log file, the start and end times of the segments that are removed are listed in the log file so you have a permanent record.

Before using time compression, be sure you start with audio that is the best quality possible. Artifacts or noise in the source content will be more pronounced when the content is accelerated. Noise in the source content also decreases the accuracy of pause removal.

Always test your content to ensure that you achieve the desired results. To run a test, encode some content by using time compression and then play it. If the results are unsatisfactory, adjust the time compression settings, and then encode the content again.

Related topics

• Customizing a session
• To accelerate or decelerate the audio and video frames
• To remove pauses from the content