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SeeDeClip visual declipper documentation


Please make sure you have read the page on Installation and the Getting started guide before you continue.

Additional notes



Initial CD clipping and level analysis

The main default control panel that appears when you start SeeDeClip represents a top-down view of the processing the waveform file goes through from input to output.

sci_analysis.png

This part of the panel shows you the filename you have opened (use File→Open, not Graph-Browse) and its format information.
If you clip on Analyse the threshold setting (in the 'declipping controls' below) determines the clips found and the entire file is scanned to find the number and type of clips in the file.
In addition the level (Peak and RMS/RMSA) are measured.
  • Altering the Clip Detect Threshold value below will affect how many clips are detected
  • Altering the Use 50ms RMS averaging (Pro version only) will affect the level values shown as that produces a slightly different result to straight RMS

Step 1: CD track de-clipping controls

This allows you to enable/disable declipping, to set the clipping threshold and to determine any limit on the dynamic range increase caused by the declipping process.

Type of declipping available (Only the Pro version has rounding):
  1. DeClipping (with 6dB cut or level compensation)
  2. Rounding within zone (does not scale the waveform)


DeClipping:

Usually to declip a waveform DeClip is selected.
sci_declip1.png

Declip lowers the track level and fills in the missing bits.

CD signal Clip Threshold

The threshold is the digital number from the maximum level found in the track (+ve and -ve) and below, to determine what exactly is a clip. For pure CD digital mastering clips this can be 1 and all the clips will be found. Many clips are however a bit 'rough' and you need a decent threshold. The default is -0.08dB and a useful default.

Clip edge lift

The no lift of clip edges is subtle and has most effect on lightly clipped tracks.
Points that actually sit on the clip level are probably limited and may need to be a bit higher.
To stop DeClip from moving these 'clip edge' points that sit right on the limit - tick this box.

  • This field is ignored for Rounding operations.

Short declip gain limit

The short clips are declipped in a fairly arbitrary manner and use a very different method than that of the longer clips. In practice this means they are highly dependant on the source material and generally need more taming. This is why the maximum gain from these is set lower than for the long clips.

Long declip gain limit

Long sections (more than 5 samples in a row) are declipped in a way that increases the dynamics and flow of the music, creating a much smoother effect. This primary declipping method - like real music, can sometimes spit out a big lump (akin to the 100 year waves of the oceans, where waveforms add together at random places). These big lumps are rare but affect the levelling capability, so this setting limits the size of the lump - only compressing the new repair when required.

Rounding: (Pro version only)

Lowering the level on a 16bit CD can sometimes reduce some of the 'life' and 'energy' of the sound, especially is there is quite a lot of low level sound, or only the odd bit is clipped. New for version 2 is rounding.
sci_declip2.png

Rounding mode uses a rounding zone to compress the declipped waveform back into the original waveform and any unused dynamic range. Rounding therefore declips the waveform without lowering the level.
Rounding basically turns a clipped waveform into a limited waveform, thus removing clipping distortion but leaving the rest of the signal unaltered. Dithering is disabled for this mode as most of the signal is unchanged.

The safety gap maintains that level between clipping and the max signal. It's the rounding equivalent of the levelling Gap between Clip and Signal.

Step 2: CD track levelling options

If DeClip is selected but levelling isn't, the standard cut in level of a track is 6dB, or ½ the magnitude of the original. This effectively turns a 16bit song into a 15bit song, and we'll use up the extra bit now with the declipped signal. When declipping occasionally a declipped signal will still clip, so this acts like a compressor - but only offending peaks are compressed.
It is worth noting that the setting a too great a long clip gain limit (above) can cause clipping only without levelling (or with levelling and -U).

sci_levelling.png

When Levelling is enabled SeeDeClip can manage the output levels of the signal, rather than just going for the 6dB cut if declipping is enabled.

Replay Gain: Use 50ms RMS averaging (Pro version only)

RMS averaging. The default measuring method is to perform an RMS level of the whole track.
However an emerging standard of 'how loud is a track' is called RMS averaging or RMS Energy Calculation.

In this case the level is computed by dividing up the track into 50ms chunks, taking an RMS measurement of those, and then averaging all of the results together.
A useful resource is:


Keep channel mismatch

Many CDs have an RMS level mismatch between the L and R channels, which in some circumstances you may wish to preserve. By default the channel levels are balanced to RMS equality.

Absolute level target

Level to aim for
This targets the RMS level to the specified one. Two things can disturb this:
  1. If the level is too high and may be clipped or not allow a gap (-g) it is lowered to suit
  2. If the level is too high and a -U (unsafe) option is used, the output will become clipped

Relative level change

Relative level to lower by. If you also use keep channel level mismatch this has an overall 'volume control' effect, i.e. both levels fall by the same about, otherwise they fall by the average amount (default).

Safety gap

This is a guaranteed gap between the peak possible and the peak signal.
It allows the DAC some dynamic (overshoot) headroom, setting 0dB will allow waveforms to approach the edge.
You can switch off the safety gap and ensure that the absolute or relative level always 'wins', but this risks re-clipping, the gap is the DeClip way of preventing any further clipping, irrespective of level controls and track characteristics.

Preview Output

sci_preview.png

To Preview the waveform, just click on 'Preview'. This causes a graph to pop up centred around the worst clip and shows a few seconds of the track. You can zoom in (click on the waveform and/or use the keyboard cursor keys and Shift) and the next preview will show you the same area.

Remember you can resize the graph window by grabbing the edges and move it with the right-hand mouse button (click-move-release) anywhere on the graph window.

Preview control

There are two additional controls for preview:
  • digital - preview a digital shaped waveform (you can toggle this (if not resampling) by pressing 'd' when on a graph).
  • orig - Show the original waveform as well together with the clip-detection threshold bands.

Unless re-samping you can switch between digital and analog view by pressing 'a' and 'd' (read more).
You can also vary the time of the preview, the smaller the faster. You can zoom into a section and press preview

Waveform Output

sci_output.png

Execute - declipping the CD waveform

If you press Execute then the file will be declipped with the selected settings and written to the output file.
You can Choose the output file specifically but will intelligently adapt as you open new input files.

If you need to convert a number of files, use the Batch file from the Tools menu.



You may now be interested in looking at the documentation for Graph Control..
To convert whole CDs, please look at the batch mode documentation.

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