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
21st Century Technology for 20th Century Content
James Hall A big challenge facing owners of legacy content is rationalising and archiving their tape and film-based media in cost effective and efficient ways, whilst also adding value. Normally the result of this is to find a low cost means of digitising the content – usually leaving them with a bunch of assets on HDD. But then what? How can content owners have their cake and eat it?
Tags: iss135 | legacy | digitising | digitizing | archive | James Hall
Contributing Author James Hall Click to read or download PDF
The making of The Heist
Tom Hutchings Shine TV has never been one to shy away from a challenge, be that in terms of using new technologies, filming ideas or overall formats: we pride ourselves on being ambitious and risk-takers.
Tags: iss135 | liveu | heist | streaming | cellular | mobile | connectivity | Tom Hutchings
Contributing Author Tom Hutchings Click to read or download PDF
Grading BBC Sounds
Simone Grattarola

The BBC has launched its new personalised music, radio and podcast app with a campaign that follows one listener’s journey from meeting Kylie Minogue in a lift to Idris Elba on a bus. 

BBC Sounds offers a single home for the BBC’s thousands of hours of audio content, including live and on-demand shows and special music mixes curated by artists.

BBC Creative, the broadcaster’s in-house creative division, took the brief to agency Riff Raff Films and Megaforce directing duo of Charles Brisgand and Raphaël Rodriguez who in turn brought on board regular collaborators Time Based Arts.

Tags: iss135 | bbc | grading | bbc sounds | davinici | resolve | blackmagic | editing | Simone Grattarola
Contributing Author Simone Grattarola Click to read or download PDF
Switching to Internet Based Distribution
Chris Clark

"An IP status check for the broadcast industry", "Resistance is futile", "IP points the way forward for the broadcast industry"...

Yes, we've read the headlines too. But rather than force you into submission, scare you, or leave you feeling like you have no other choice, we want to give you the information that helps you to make a sensible decision about Internet-based distribution.

So what’s stopping you from making the switch right now?

Tags: iss135 | ip | internet | distribution | cerberus | Chris Clark
Contributing Author Chris Clark Click to read or download PDF
Future proofing post production storage
Josh Goldenhar Advancements in NVMe (Non-Volatile Memory Express), the storage protocol designed for flash, are revolutionising data storage. According to G2M Research, the NVMe market will grow to $60 billion by 2021, with 70 percent of all-flash arrays being based on the protocol by 2020. NVMe, acting like steroids for flash-based storage infrastructures, dynamically and dramatically accelerates data delivery.
Tags: iss135 | nvme | sas | sata | it | storage | post production | Josh Goldenhar
Contributing Author Josh Goldenhar Click to read or download PDF