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The first step is to select the audio file(s) you want to transform, by adding them to the "Input Files" list. Adding input files can be done in three ways:
The following audio file formats are supported:
Sample rates from 8 kHz to 384 kHz are supported (as long as enough memory is available). Note that the Tachyon time stretching algorithm already fully interpolates inter-sample values during the transformation, so there is no reason to use sample rates higher than 44.1 or 48 kHz, unless you actually have ultrasonic frequencies to transform. In particular, up-sampling 44.1 or 48 kHz files before transforming them will just make the process significantly slower with no gain in quality.
Hint: it is possible to add all the files of a playlist in the ".m3u" or ".m3u8"
Mono, stereo and multi-channel files (up to eight channels, such as "7.1") are supported. Multi-channel files should only be used when the channels correspond to spatial positions (such as left and right for stereo, or 5.1 surround). You should NOT use multi-channel files in which the different channels correspond to different "tracks" (such as vocals, bass, etc). The reason is that the Tachyon algorithm will lock the phase of the different channels to preserve the stereo (or surround / spatial) field. Locking the phase between unrelated tracks will result in a deterioration of the quality: in that case, each track must be extracted in a separate file using another application such as your DAW before they are transformed by the Tachyon application.
In the "Input Files" list, you can click on a file to select it. Use the Ctrl key while clicking to select multiple files. Use the Shift key while clicking to select a file range. Clicking while holding the Ctrl key on a selected file deselects it.
The files in the "Input Files" list are not copies of the original files. If you delete or change one of the files from another application, the list will not be automatically updated and errors might result.
The following menu items apply to the files in the "Input Files" list:
By right-clicking on a file, a contextual menu appears with the following actions:
An input file can be selected by clicking on it. Hold the Shift key while clicking to select a range of files. Hold the Ctrl key to select multiple files, or to deselect files that are already selected. The button only transforms the files that are selected. The transformation parameters described in the next section only applies to the selected files as well.
Once one or more file is selected in the "Input Files" list, the following panel appears at the bottom of the application's window:
Notes (for all parameters in all three parts):
) appears on the right side of the parameter.
When you change parameters, they are memorized (for each input file) but they are not applied until you hit the button. Changes are not applied to files that are already in the "Output Files" list (files that are already transformed, that are being transformed, or that are waiting to be transformed).
The next sections discuss the three parts in more details: Time Stretching Factor, Transform Settings and Output Settings.
The "Time Stretching Factor" part has a drop-down list as shown in the following figure:
These options are not different settings: they all correspond to the time stretching factor, but each of them allows you to specify it in a different way.
More precisely, the options are the following (click on an item to expand / collapse):
Specify the length of the transformed file as a percentage of the length of the input file. For example, specifying "200%" will make the transformed file two times longer, and hence two times slower. "50%" makes it half the length, and hence two times faster.
The slider (1) only allows you to specify a change between "50%" (two times faster) and "200%" (two times slower). However, you can specify a change between "25%" (4 times faster) and "400%" (4 times slower) by typing the value directly in the text field (2).
By default, the length is given as a percentage of the length of the input file, when the "" radio button is selected. By selecting the "" radio button, you can specify the length change as a positive or negative percentage. In this mode for example, twice the length is "+100%" rather than "200%", and half the length is "-50%" instead of "50%".
Specify the length of the input file and the length of the transformed file.
By default, the length of the input file is set to the length of the selected input file(s) and cannot be modified. By unchecking the "" check box, you can specify a fictive input file length.
In all case, the ratio between the specified lengths is used as the time stretching factor. Length is specified in hours, minutes, seconds and microseconds (the last field is microseconds, and not sample frames).
Warning: when working with audio files in a compressed format (.mp3, .m4a, etc), the "" length might be inaccurate. A warning icon () is displayed in the bottom right of the panel in that case. Choose from the menu (or from the context menu on the warning icon) to retrieve the exact length.
Specify the playback speed of the transformed file as a percentage of the playback speed of the input file. For example, specifying "200%" will make the transformed file play twice as fast. "50%" makes it play at half speed.
The slider only allows you to specify a change between "50%" (two times slower) and "200%" (two times faster). However, you can specify a speed change between "25%" (4 times slower) and "400%" (4 times faster) by typing the value directly in the text field.
By default, the playback speed is given as a percentage of the playback speed of the input file, when the "" radio button is selected. By selecting the "" radio button, you can specify the speed change as a positive or negative percentage. In this mode for example, twice the playback speed is "+100%" rather than "200%", and half the playback speed is "-50%" rather than "50%".
Specify the input file tempo and the transformed file tempo, in BPM (beats per minute). The tempo of the input file may or may not correspond to the actual tempo: the application simply uses the ratio between the two specified tempo values as the time stretching factor.
For example, specifying "120" in the "From:" field and "180" in the "To:" field will make the audio file 50% faster (like a change from 120 BPM to 180 BPM).
Note: there is no tempo detection feature. The tempo of the input file (in the "From:" field) must be set manually.
Specify the length of the input file and the length of the transformed file. Both values are specified as a number of audio frames. By default, the length of the input file is set to the length of the selected input file(s) and cannot be modified. By unchecking the "" check box, you can specify a fictive input file length. In all case, the ratio between the specified lengths is used as the time stretching factor.
Note: an audio frame corresponds to one audio sample in each channel. For a mono file, the number of audio frames corresponds to the number of samples. For a stereo file, the number of audio frames is half the number of samples. A 48 kHz file for example always has 48000 audio frames in one second, regardless of the number of channels.
Warning: when working with audio files in a compressed format (.mp3, .m4a, etc), the "" length might be inaccurate. A warning icon () is displayed in the bottom right of the panel in that case. Choose from the menu (or from the context menu on the warning icon) to retrieve the exact length.
If the audio file to transform is the audio track of a video, this option let you specify the video playback speed of the original file, and the video playback speed of the transformed file. Both values are specified in video Frames Per Second (FPS).
For example, a typical NTSC to PAL conversion plays a video track originally at 23.976* FPS (NTSC) on a 25 FPS system (PAL). In that case, to stretch the audio accordingly, enter 23.976 in the "From:" field, and 25 in the "To:" field.
*This value originates from a 29.97 FPS (the true NTSC FPS) video track converted by an approximate 24/30 ratio. An exact conversion of a 29.97 to a 25 FPS video track is generally difficult to perform with good image quality, which is why the resulting video track is typically at 23.976 FPS instead of 25. However, in case the video track is converted exactly (with an exact 29.97/25 ratio), there is no need to stretch the audio track.
Specify the time stretching factor directly as the ratio (quotient) between:
A value of "2.0" for example means two times slower (two time longer) when the "" radio button is selected, and two times faster (two time shorter) when the "" radio button is selected.
The different options above do not correspond to different parameters. They all correspond to the time stretching factor, but specified in a different way.
If you specify the time stretching factor using the option and set it to 125% (for example) as follows:
More generally, any time stretching factor specified using any of the options is then reflected in the other options.
For each file, the chosen time stretching factor appears on the "Input Files" list, on the third column (1) of the figure below. The value here is always displayed as a ratio between the output length and the input length (such as "2.0" for two times longer). The value that is displayed might be rounded, but internally the exact value is remembered and used. By moving the mouse over it and waiting a few seconds, a tooltip appears (2) and displays the exact value (as a ratio), as well as the value as a Length Change and as a Speed Change.
This part allows you to change advanced transformation settings: the Quality, the Transient Mode, and the Crisp / Smooth balance.
Click on the button to modify the advanced settings. The following window opens, and allow you to modify the values for the settings.
The settings discussed here apply to the selected input file(s). See section 4.3.1 to change the values to apply by default to input files that are added.
Let you change the time stretching quality. A lower quality also means a faster processing speed.
The possible values are the following:
Notes:
This settings controls transient detection and processing. It is not available when the quality is set to 1.
Note: while not directly related to the transient sensitivity, the Dense mode is generally the most sensitive (detects the highest number of transients), whereas the Soft is generally the least sensitive (detects the lowest number of transients).
When choosing the transient mode, be aware of the following limitations:
This is an advanced setting. 95% of the time, the default value of 0.0 is the best one.
Change this value with care. It is advised to always compare the result with the default 0.0 value.
To understand this setting, observe that time stretching algorithms generally fall into two categories:
From a musical point of view, time-domain approaches are better at preserving vibrations and grain (fine texture, or fast amplitude variations in the 10 Hz - 100 Hz range), but may introduce a granular or metallic character to the sound. Frequency-domain approaches tend to smooth the sound, and may introduce a "phasy" or reverberant character.
The Tachyon algorithm can behave either like a time-domain approach, a frequency-domain approach, or anything in between. This is what the Crisp / Smooth setting determines.
The slider allows you to choose a value between -0.5 and +0.5. By typing a value directly in the number field, you can specify a value between -1.2 (the minimum) and 1.2 (the maximum).
A few hints on how to choose the value:
Negative values tend to deteriorate the quality on string ensembles and plucked-strings (guitar and similar).
Positive values tend to deteriorate speech and voice by making them "distant", "reverberant" and "phasy". Extreme values (> 1.0) can also introduce smearing of transients.
Hint: in general, if the individual tracks of a mix are available, processing each track separately can result in higher quality than processing the final mix. The reason is that the Transient Mode and Crisp/Smooth settings can be adjusted for each track depending on its nature. On the other hand, the left and right channels of a stereo track (or the channels of a extended-stereo track such as 5.1 or 7.1) must always be processed together, or else the stereo and/or spacial field may not be preserved.
When processing the individual tracks of a mix separately:
This part allows you to control the output files, notably the format in which they are saved and the resolution (bit depth).
Click on the to modify the output settings. The following window opens, and allow you to modify the values for the output settings.
The output settings are the following:
Time stretching preserves the average loudness (or RMS level), but does not preserve peak levels. As such, peaks may fall outside of the maximum -1.0 - 1.0 range in the transformed files. These peaks are fully preserved when a 32-bit float format is used, but they result in clipping when a 16-bit or 24-bit format is used. The Normalize to prevent clipping option can be used to automatically lower the volume of the output file whenever a peak would fall outside of the -1.0 - 1.0 range. When this option is used, the loudness is not preserved and the transformed file can be softer.
When a 32-bit float format is used and peaks are above the maximum -1.0 - 1.0 range, the peaks are fully preserved, and a suitable normalization or dynamic range compression can be performed in a DAW that supports 32-bit float files with out-of-range peaks. Note that until normalization is done, the file will still clip when played as soundcards generally do not support out-of-range peaks.
The output settings discussed above apply to the selected input file(s). See section 4.3.1 to change the default values to apply to input files that are added.
Select one or more files in the "Input Files" panel, and click on the button to transform them.
It is also possible to right-click on a file in the "Input Files" panel, and to choose the context menu.
The transformation will use the parameters that have been set for each file, as discussed in section 3.2.
Time stretching a file takes time. On a 3 Ghz processor, it typically takes about 10 minutes to transform 1 minute of stereo audio at 44 kHz with the maximum quality setting. When you click on the button, the files appear immediately in the "Output Files" panel, but the transformation has just started, and may not have finished yet.
By default, when you click the button, the selected files are removed from the "Input Files" panel. To keep them, hold the Shift (⇧) key while clicking. You can also right-click on a file and choose the context menu. This is useful if you want to transform the same file multiple times, using different parameters.
The "Output Files" panel (shown in the next figure) shows all the transformed files, but also the file currently being transformed, and the files waiting to be transformed.
An icon on the left of each file indicates the state of the transformation:
(rotating): the transformation is in progress. The progress (in percent) is visible in the last column (2) in the picture above. The middle column (1) indicates the length of the transformed file so far. This value increases as the file is transformed.
: the transformation is finished, and the file is being saved to the disk. This stage is generally quick. However, if you have a slow hard disk, the saving progress (in percent) is visible in the last column (2).
: metadata are being added to the transformed file.
: the transformation is finished and the file has been fully saved to the disk. At this stage, it is possible to open the file in the system explorer, or in other applications. Tachyon will not touch the file anymore (unless you choose the menu).
: the transformation has not started yet and is waiting for a CPU core. Tachyon can transform a certain number of files at the same time (generally given by the number of CPU cores, but this can be changed as described in section 4.3.2). As soon as a previous file has finished, the transformation of this file will start if it is the next on the list.
: the transformation has not started and is waiting for RAM. This can occur on systems with many CPU cores, but relatively few RAM available.
: the transformation is paused. This only occurs when you explicitly choose the menu. The transformation can be resumed by choosing the menu.
The following menu items apply to files in the "Output Files" list:
By right-clicking on a file, a contextual menu appears with the following actions:
The and buttons under the "Output Files" list do the same as the and contextual menus.
Current: 3 Detailed Tour