It’s everyone’s worst nightmare; you put the tape into the deck knowing you have one or two chances of capturing a fragile tape.
You cross your fingers, hoping it’s going to look OK… it doesn’t! Don’t worry – all is not lost!
Even some of the worst tape faults can be fixed and below I identify some of the more common issues you will come across and provide some hints and tips as to tools to try inside PFClean’s Telerack and Workbench to help make your video artefacts disappear post-capture. So let’s fast forward…
Fixing tape defects with Telerack
One of the features of PFClean is the powerful Telerack video restoration engine. With an emphasis on speed and a focus on the most common defects, this is an ideal way to restore tape-based media, especially in cases where a fast turnaround and large volume of media are involved. Below is a list of common tape faults with examples, along with tips on how to identify them and how they can be easily fixed in Telerack.
Tape Dropouts
This example shows the repair results using the Telerack Fix Streaks tool
Tape dropouts mainly present themselves as a horizontal line, sometimes teardrop-shaped and usually bright, and appear on screen for one or two frames with staggered intensity. Occasionally these can be persistent through an entire tape.
Off-Lock Errors
Here we can see the repair using the Fix Streaks and Fix Bands tool
Off-lock errors are like a dropout but larger and with greater frequency, with a band of colour or misregistered image usually lasting no more than a frame. They are a common sight on old and worn analogue tapes.
Timebase Corrector Dumping
To repair this issue image stabilisation was used
Timebase corrector dumping is sometimes referred to as a bump. This problem presents itself as a brief shift in image position, normally vertically, and can range from very mild to very severe.
Excessive Tape Noise
The De-noise effect is used to strip back multiple generations of analogue noise
Excessive tape noise will appear in tapes that are multiple generations away from the original source and/or have started to deteriorate with age. Additionally, material that originated on legacy camera systems can be susceptible to excessive noise due to its low sensitivity.
Chroma Subsampling
The Chroma Resample effect in the Telerack toolset provides a quick high quality fix to this footage
High chrominance areas can lack fidelity, especially where the source is 4:1:1 or 4:2:0. It is most noticeable in areas of red along diagonal surfaces. Older professional and commercial analogue formats and lower-quality digital tape formats all suffer greatly from a lack of chroma information.
Chroma Fringing
The coloured shimmering is dramatically reduced using the Chroma Cleanup effect.
Chroma fringing can appear in high-value chrominance and specular detail. This is caused by crosstalk in the luma and chroma signals. Next time you watch an old television series, watch areas of high detail and you might notice a coloured shimmering. This is chroma fringing.
Tape Banding
Hard to remove manually, the Fix Bands tool makes short work of these dark luma bands.
Tape banding appears as horizontal light or dark bands across the image lasting over a number of frames. Rapid changes in luminance within a scene can sometimes exacerbate this problem.
Flickering, Scratches and Dirt
These artefacts can be removed easily using the Dustbust, De-Flicker and Fix Scratch effects.
Tape material that has been telecined from 16mm and 35mm can suffer all the artefacts that originate in the original film elements. Typically, archive material that’s been transferred to tape suffers from excessive dirt and scratches.
Scanline Flicker
This footage from the 1970s shows the results of a successful restoration using the Scanline De-Flicker effect.
Scanline flicker is minor variances in luminance values between scanlines. It is sometimes caused by variances in field luminance. Not to be confused with rolling bands.
Fixing tape defects with the Workbench
The Telerack is focused on high-performance video restoration. Ideal for the hours and hours of tape that can be found in archives. However, some fixes are so severe they require the precision that can be found in PFClean’s powerful Workbench. In the table below we will help you identify these severe faults and suggest Workbench tools to help you restore your tape.
Momentary Head Clog
The Fix Frame effect was used to remove the misaligned image area and the shift in luminance.
Momentary head clog is a horizontal band or sometimes an entire frame of misaligned and warped image, usually for a single frame. The distortion can be complex and requires the rebuilding of a portion of the frame.
Scratched Tape
A combination of the Fix Frame and Fix Bands effects were used to remove the scratches.
Scratched tape is common in formats such as 2″ Quad and TypeC where the physical tape is exposed to the environment. This artefact presents itself as a thin horizontal line of misregistered image that remains static and constant for the duration of the scratch. In a way, it is very similar to a film scratch but horizontal.
Transverse Tape Damage
Using a combination of the Fix Frame and Paint tools a successful fix was made in this example.
Transverse tape damage is a horizontal band of misregistered image that rolls up the screen, usually from bottom to top. This is a fairly common fault in old analogue tapes. Next time you watch an old VHS, look out for this fault.
Capstan Servo Off-Locks
Using the Stabilise, Fix Frame and Pan & Scan effects has fixed this tape error.
Capstan servo off-lock errors are moments of picture instability and sometimes picture breakup, along with wow distortion in audio. Normally this is seen at the top or bottom of the screen.
Mild Tape Mistracking
Panning & Scanning the image removes the undesired area at the top of the image.
Mild tape mistracking appears as a thin band at the very top of the screen with segmented or misregistered images. It can be fairly constant if the tracking was not adjusted correctly during the capture.
Severe Tape Mistracking
While not easy, a combination of Painting and using the Fix Frame were used to rebuild the entire image over several frames.
Severe tape mistracking is the breakup of the entire image resulting in multiple dark and light lines with bands of misregistered image, flickering, and loss of colour. It is possibly the most complex error you will encounter and the most difficult to fix. Sometimes this is why it is useful to have a dub of the tape even if it is of lesser quality so that it can be used to rebuild the images.
Lifted Blacks
Lifted blacks can easily be corrected by using the video grade effect and observing the scopes.
Lifted blacks are caused by transfer errors in the dubbing process. Sometimes this can occur when standards converting from one region to another. NTSC-originated material can look milky on PAL systems if not properly converted.
Chroma Phase Convergence Error
A clip like this can be salvaged by applying the grading tools.
Chroma phase convergence errors can be observed via a vectorscope and waveform where chroma phase is out of alignment. In the example above, this was caused by material from one tape being spliced into the master without correct calibration.
Blocking and Compression Artefacts
The Blocking Reduction effect smooths out any undesired areas where image breakup has occurred.
Highly compressed formats such as mini DV can suffer macro blocking and image breakup during high dynamic and kinetic shots resulting in squares and mosquito noise around detail.
Persistence Trails
The Paint effect was used to paint out the trails in this particular example.
Persistence trails are luminance/chroma trails that appear in bright highlights and chroma. They appear when the luminance value has not had time to reset to zero causing a ghosting trail or comet. They are common in material recorded using cathode ray tube cameras from the 1930s to the 1980s.
Horizontal and Vertical Sync Pulse Loss
Paint, Fix Frame and Pan & Scan effects were all used to fix this error.
Sync pulse loss errors show up as a merging of the adjoining frame with a vertical or a horizontal breakup in the image. If this error occurs, it’s normally accompanied by one or more of the errors described above on the surrounding frames.
Links
Sony has a great page here showing their milestones in broadcast history from the early 1950s through to the modern-day.
The clip examples featured in the article are from the Bolshoi Ballet restored for SKY ARTS.
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