Wibbly Wobbly Waveforms


TV-Bay Magazine
Read ezine online
The very first analytical electronic instrument, developed in the late 1890s, was the oscilloscope. This used a cathode ray tube (CRT) to paint a graph of voltage on the Y axis versus time on the X axis. Once television became a practical reality in the 1930s, the same instrument was applied to the video output from the camera and became the very useful waveform monitor.

Early television cameras were delicate and temperamental beasts so a waveform monitor was an essential tool for examining picture levels at every part for the programme production and transmission chain. PAL or NTSC video signals are sensitive to a variety of transmission or recording nonlinearities and problems such as un-terminated cables. Every analog studio feed has to be precisely timed to ensure it stays in sync. Constant checks have to be made using the waveform monitors to ensure all the timing adjustments were perfect. Colour television gave the waveform monitor many new roles as even more adjustments were needed to make analogue transmission work properly.

Digital picture information is relatively robust and does not usually get corrupted at each regeneration or link. Precise signal timing is no longer crucial; every equipment input is normally capable of re-timing itself correctly or even has an integral synchroniser. CRTs have vanished from waveform monitors and are increasingly rare in the home but modern digital test instrument using LCDs or rasterizers look much as they did in the early days.

So why would you want to look at luma (picture brightness information) portrayed on the same analogue style instrument?

Modern cameras are essentially analogue, even after the big switch to digital transmission, and they still incorporate an automatic iris. Add in the human operator variables and there is always every chance for the picture to be less than optimal, particularly when matching cameras. There could also be differences in lenses, optics and sensors. Incorrect gamma settings can give rise to crushed blacks for instance. All can be easily spotted on a waveform monitor. There are many additional special monitoring modes to help with colour balance, such as the RGB parade. This simply shows all signals side by side or overlaid on a common timebase for easy comparison.
The most common timebase for monitoring is 1H: one horizontal scan line period. Usually all the frame lines are displayed overlaid in this mode so only horizontal features stand out. Most instruments can also alternatively show a frame-based timebase but traditionally still portrayed on the same horizontal time axis. Some unconventional instruments have a waveform frame view display turned though 90 degrees. This view makes for a better correspondence with the actual picture analysed.

Transmission problems that could give rise to blocking and quantisation errors also exist in the digital world. Transcoding and remixes can also affect the dynamic picture range. Waveform monitor displays are therefore still very much in use but no longer in a separate box like the old analogue instruments. Today they are always combined at least with a vectorscope. These features can be integrated into the monitor itself. The displays are in most cases only an indication of the levels with a crude graticule.

Fully featured test instruments with calibrated displays can provide much more detail and the ability to switch graticules and scaling as well as homing in on a region of interest in the image. These can be still found in a stand-alone box with or without a built-in screen. More often the waveform can be brought up on the computer monitor as a tool or plug-in to an editing or grading package. These too can have limitations. Sometimes their speed is well below real-time or the is size quite small due to the limitations of running within the editing software.

For real-time conventional 2D images, the Cel-Soft Reel-Check Solo uses PC software image processing that is fast enough even for 4K as well as 2K/HD monitor windows in multiple views, audio or other displays. And there is no special hardware. This type of software product can replace the rasterizer or stand-alone box.

For 3D TV production or post, the Cel-Scope3D software creates high-precision waveform monitors which can be combined so that left and right eye image luma or RGB are superimposed for comparison and matching.

A waveform monitor is very similar in concept to the oscilloscope in many ways. Digital processing has now completely done away with vacuum-tube technology but still provides the familiar waveform styles that are easy to understand and can provide a comforting consistency in a studio suite or on-set.



Robin Palmer is Managing Director of Cel-Soft and is habitually involved with solutions for 3D & TV technology.

Tags: iss070 | cel-soft | cel-scope3d | waveform | monitoring | vectorscope | N/A
Contributing Author N/A

Read this article in the tv-bay digital magazine
Article Copyright tv-bay limited. All trademarks recognised.
Reproduction of the content strictly prohibited without written consent.

Related Interviews
  • Calrec Callisto at IBC 2013

    Calrec Callisto at IBC 2013

  • Tektronix at IBC 2016

    Tektronix at IBC 2016

  • Tektronix at IBC 2014

    Tektronix at IBC 2014

  • Atomos with the Samurai Blade on BroadcastShow LIVE at IBC 2013

    Atomos with the Samurai Blade on BroadcastShow LIVE at IBC 2013

  • JVC monitoring solutions DT-G, DT-E, DT-U, and DT-V range at BVE 2018

    JVC monitoring solutions DT-G, DT-E, DT-U, and DT-V range at BVE 2018

  • IP, 3G-SDI + HDR generation, analysis and monitoring from Phabrix NAB 2017

    IP, 3G-SDI + HDR generation, analysis and monitoring from Phabrix NAB 2017

  • Apantac monitoring over IP at NAB 2016

    Apantac monitoring over IP at NAB 2016

  • Wohler MPEG Monitoring Series at IBC 2014

    Wohler MPEG Monitoring Series at IBC 2014

  • Wohler MPEG Monitoring at BVE 2014

    Wohler MPEG Monitoring at BVE 2014

  • Bridge Technologies QoE Monitoring with Mobile Videowall Display at IBC 2013

    Bridge Technologies QoE Monitoring with Mobile Videowall Display at IBC 2013

  • The Telos Alliance at IBC 2016

    The Telos Alliance at IBC 2016

  • Wohler at IBC 2016

    Wohler at IBC 2016

  • Phabrix Qx at IBC 2015

    Phabrix Qx at IBC 2015

  • Phabrix TAG and Rx at IBC 2015

    Phabrix TAG and Rx at IBC 2015

  • NUGEN Audio at BVE 2015

    NUGEN Audio at BVE 2015

  • Phabrix RX series at IBC 2014

    Phabrix RX series at IBC 2014

  • Volicon Products at IBC 2014

    Volicon Products at IBC 2014

  • Volicon at IBC 2014

    Volicon at IBC 2014

  • Wohler DPP at BVE 2014

    Wohler DPP at BVE 2014

  • Wohler Technologies on BroadcastShow LIVE at IBC 2013

    Wohler Technologies on BroadcastShow LIVE at IBC 2013

  • Volicon on BroadcastShow LIVE at IBC 2013

    Volicon on BroadcastShow LIVE at IBC 2013

  • Bridge Technologies PocketProbe App at NAB 2013

    Bridge Technologies PocketProbe App at NAB 2013

  • Sound Devices at NAB 2013

    Sound Devices at NAB 2013

  • TSL Products at NAB 2013

    TSL Products at NAB 2013

  • TSL Systems at BVE 2013

    TSL Systems at BVE 2013

  • TSL Products at BVE 2013

    TSL Products at BVE 2013

  • Oxygen DCT at BVE North 2012

    Oxygen DCT at BVE North 2012

  • RTW at NAB 2012

    RTW at NAB 2012

  • TSL at NAB 2012

    TSL at NAB 2012

  • Qualis at NAB 2012

    Qualis at NAB 2012

  • Digital Nirvana at NAB 2012

    Digital Nirvana at NAB 2012

  • Leader at IBC2011

    Leader at IBC2011

  • Murraypro at IBC2011

    Murraypro at IBC2011

  • DK Technology at IBC2011

    DK Technology at IBC2011


Related Shows
  • Sony monitoring at BVE with Den Lennie

    Sony monitoring at BVE with Den Lennie


Articles
What content providers need to know about OTT
Hiren Hindocha As OTT (Over-The-Top) technology has gotten more mature and established robust standards over the years, the concept of OTT monitoring is gaining popularity. With customer expectations soaring, it’s vital for OTT providers to deliver superior quality content. To deliver Quality of Experience (QoE) on par with linear TV broadcast, the entire system, starting from ingest to multi-bitrate encoding to delivery to CDN must be monitored continuously.
Tags: iss134 | ott monitoring | qos | logging | compliance | dash | atsc | cloud | Hiren Hindocha
Contributing Author Hiren Hindocha Click to read or download PDF
Giving Welsh sport a global audience
Adam Amor From the Ospreys Rugby Union team, to the Football Association of Wales, as well as national cycling, swimming and boxing coverage, Port Talbot based Buffoon Film and Media has been heavily involved in putting Welsh sports on the world stage.
Tags: iss134 | blackmagic | atem | buffoon | micro studio camera | Adam Amor
Contributing Author Adam Amor Click to read or download PDF
An Obituary to Timecode
Bruce Devlin - new A stoic and persistent character that stubbornly refused to change with the times, Timecode has finally passed on, but no-one has noticed. A long-lasting industry veteran, Timecode was brought into this world at an uncertain date in the late 1960s due to the needs of analogue tape workflows and the demand for synchronisation between audio and video devices. A joint activity between SMPTE and the EBU led to the work on Time and Control codes starting its journey to standardisation in the early 1970s.
Tags: iss134 | timecode | smpte | ebu | edit | Bruce Devlin - new
Contributing Author Bruce Devlin - new Click to read
Accelerated Workflows with eGPU
Mike Griggs From the UK’s National Trust to magazine publishers to manufacturers, digital content creator Mike Griggs has a wide and varied portfolio of clients for whom he creates 3D art, motion graphics and multimedia exhibits. A typical day might involve sampling birdsong near Virginia Woolf’s country estate or creating 3D animations for VR. To keep on top of these demands, Griggs wanted to take the full power of the GPU computing revolution on the road.
Tags: iss134 | sonnet | egpu | amd | post production | editing | Mike Griggs
Contributing Author Mike Griggs Click to read or download PDF
GoPro HERO 7 Review
Tim Bearder When I heard I was filming a nature restoration project in the pouring rain this week I was excited. WHY? No Cameraman enjoys the rain, surely but this time I was enthusiastic because I knew this would be the perfect opportunity to try out the brand new GoPro Hero 7 Black Edition.
Tags: iss134 | gopro | hero 7 | review | liberal media | Tim Bearder
Contributing Author Tim Bearder Click to read or download PDF