Clicks into DSF or PCM (FLAC, WAV, AIFF, etc.) files extracted from ISO (1-bit audio) is fairly common occurrence.
«How extract ISO without clicks?» is one of most popular questions associated with conversion ISO 1-bit audio to music files.
Main issue here is plenty of different click types.
There is no general recommendation: how to fix any kind of these clicks.
Here we consider several possible types and try recommend action(s) for fixing each one.
You can try clicks either experimentally or after analysis of converted audio file content.
Let me begin from click reasons currently known me:
May be in the future will discovered new reasons. ISO surprise me not once.
Whether or not we hear clicks, depend on hardware software playback processing, volume level of amplifier.
Audio content of ISO can be extracted to DSF as is (without changes, bit-perfect extraction).
There no resampling and other processing.
If these files will be monitored at audio player with gapless playback ability, we won't hear clicks.
If the tracks are played back separately or other order than into the album:
Track 1 - probably click at end,
Track 2 - probably clicks at begin and end,
Track 3 - probably click at begin.
Click level depend on sample level at border of track.
Also click level depend on difference of sample levels at common border of next tracks.
For ability random order playback of the album’s tracks, recommended use SmoothDC processing.
SmoothDC click suppressing at begin and end of a audio tracks
Smooth DC is fast fade in/out (gain control) at begin/end of a audio track. Gain changing curve has special form that allow approach track from full volume to zero and vice versa smoothly.
Two tracks, processed by SmoothDC have common value at border - zero.
So there is no level "stair" between tracks, that can cause click.
Short time of the fade in/out is designed to minimisation of impact to track.
Special form of changing gain during time is designed for more smooth transient at track border(s).
Tradition resampling re-initialised at begin of each converted track. Conversion ISO to PCM may be considered here as resampling too.
It is good for batch audio conversion of mixed unrelated tracks.
But for album type with general DC bias re-initialising will generate transient processes (noise) at begin and end of the track.
At common spectrum of merged next tracks we can see it as splash (line at track border).
For minimal border changes recommended use gapless conversion, where all album tracks processed sequentially in album order.
Proper playback of resampled files should be gapless. Otherwise clicks can appear probably.
Audiophile Inventory developer