input file : source soundfile
output file : destination soundfile (when marked)
or result.wav (for unregistered files)
processing mode : global
You can use this tool to change duration of the recording (stretch or compress the time duration of a sound) without altering the pitch.
The time scale changes can be controlled in three different ways.
The slider and the associated box can be used to define the new length of the recording as a percentage of the old one. The two boxes situated in the New length group allow you to set the desired length of the recording in the units of time or in bytes.
For large values of the scaling coefficients the uniform scaling of speech signals may produce unnatural effects, e.g. the slowed down speech may show “drunken” characteristic and the speeded up speech may be difficult to understand. The explanation is simple – people do it differently. In actual rate-changed speech, unvoiced sounds such as consonants and fricatives, do not undergo the same scaling as the vowels. To improve naturalness/intelligibility in time-scale modified speech, check the Dynamic rate adjustment box – in this case the speech-adaptive rate will be applied. Since under adaptive scaling unvoiced sounds remain essentially intact, the overall expansion/compression rates, reflected by the changes in the length of the output file, are smaller than the nominal (declared) rates. Since the actually achieved modification rate depends on the voiced/unvoiced proportion, which is specific for a given recording, its value is difficult to predict prior to processing.
The Precision coefficient allows you to trade off between the quality of time scale modification and the speed of processing. Since the results are pretty insensitive to the simplifications introduced to achieve faster processing, in most cases you can safely set the Precision coefficient to 10% without causing a noticeable degradation of the produced sound.
Audition controls allow you listen to the results of DART Time Compressor/Expander while you change the Time Compressor/Expander controls. You can compare the results of Time Compressor/Expander to the original recording by switching between Play Result and Play Source. Choices in the Range control allow you to select starting and ending points in the soundfile that you are auditioning.
Press the Play Result button to hear the results of Time Compressor/Expander digital audio processing. You can modify the Time Compressor/Expander parameters while playing results. The green Ready light indicates the Time Compressor/Expander parameters you set have been processed and are ready to play. When you change parameters, the light goes off until your new settings have been processed.
Press the Play Source button to hear the original soundfile. All Time Compressor/Expander processing is bypassed.
Use the Overview Bar to set the position of the cursor. The Overview Bar is the unlabelled gray rectangle at the very top of the Time Compressor/Expander panel. A yellow vertical line in the box represents the cursor position.
Selections in the range box allow you to choose the start and end points of the soundfile you are auditioning (from cursor, entire file, local, block). With all choices, Time Compressor/Expander plays in a loop, jumping to the start point you choose when the end point is reached. Please note: setting parameters modifies the complete soundfile not just the portion you audition.