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May/June 2020

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TECHNOLOGY www.postmagazine.com 33 POST MAY/JUNE 2020 t's been a year since Tektronix Video merged into the Telestream business. The move reflected the synergy between the Tektronix test & measure- ment tools and Telestream's file-based media workflow, media streaming and delivery technologies. It also extended Telestream's portfolio in the video test, monitoring and quality assurance areas. The focus for the Telestream video and audio test solutions has been on dealing with the transition from SDI to IP, addressing the needs of those producing content using HDR and wide color gamut, and preparing for content origination using 8K formats. These are disruptive technologies, but arguably, HDR is presenting such big challenges within the production and post envi- ronments, we believe that it's driving a requirement for a whole new set of tools and workflows. Our Prism waveform monitor platform directly addresses many of these concerns. For production, Prism can be used on a digital image technician (DIT) cart and connected to an SDI output from an NLE. For outside broadcast, Prism is widely deployed into the camera shading and technical QC positions on the truck. In a post environment, Prism would be used in an editing room, with SDI or IP connections, which allow users to see the actual signal that will be delivered through the mastering process rather than a proxy copy on the editing system. Since re-shoot costs are very expen- sive, proper shooting becomes more im- portant than ever. Prism can be used to match color and dynamic range across all cameras so that any changes in post can be applied equally and consistently. In addition, if both the production team and post team are using Prism, it makes it easier for the them to communicate approaches or changes that could be made to improve the workflow based on objective measurements. A reference monitor can't be relied upon to make adjustments, as it provides no true indication of exposure levels. Applying an HDR image to a standard monitor will produce a washed out im- age, which can be misleading. Although we can apply a LUT to compensate, it may not reflect the final desired image. The real power of HDR is to create realistic images, and that relies on several things: understanding how much of the screen is being driven into the HDR lev- els, understanding what is happening in the blacks of the image, and understand- ing what area of the screen is driven at what levels. To address some of these chal- lenges, Prism offers tools that include Stop Waveform, False Color Displays, Light Meter and a CIE chart. The Stop Waveform eases the measurement of exposure and HDR. HDR and exposure is all about light levels and the Stop dis- play provides all measurements in light levels (Nits or Stops). There's no need to convert the IRE or mV measurements to light. A user can immediately see the Stop difference between points of inter- est on an image. False Color Displays is a useful tool for managing exposure. It allows oper- ators to read exposure levels directly from the image. The way Telestream has implemented false colors is that we have allowed the user to control which colors and thresholds will be displayed. By se- lecting only the luminance levels that are important, it provides easy interpretation and avoids a whole rainbow of mislead- ing colors. The Light Meter display enables different exposure measurements from different parts of the screen or image in Stops or Nits. The vectorscope is traditionally used for color management, but as different color spaces are applied, it has the effect of shifting the colors, which is seen as a trace rotation and a move in the position of the color markers. As different gamma curves are applied for PQ or HLG, the vector trace will appear smaller and be- comes more difficult to read. Prism can compensate for this by using a LUT, but color shifts and trace compression add complexity when mastering SDR and HDR content in different color spaces. An alternative to using a vectorscope is the use of a CIE chart. It's very easy to see where the color images are in three defined color gamuts: Rec 709, DCI-P3 and Rec 2020. Today's SDR workflows consist of a waveform monitor to measure exposure levels in millivolts, a vectorscope and a picture display to confirm what is being looked at. By moving to a Stop Waveform, which is all measured in light; a CIE chart, which will allow for work across the three-color spaces easily; and using False Color Displays that will show either gamut or selected exposure levels, production can guarantee they are getting the most out of these new formats. TELESTREAM SOLUTIONS ADDRESS HDR CHALLENGES BY IAN VALENTINE VP OF PRODUCT MANAGEMENT TEKTRONIX VIDEO BUSINESS UNIT AT TELESTREAM WWW.TELESTREAM.NET I A LOOK AT PRISM'S PLACE IN PRODUCTION & POST Telestream offers solutions that go beyond the limitations of a vectorscope.

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