Occasionally, talks about broadcast topics can be a little dry. Not this one which discusses aspect ratios. For those who feel they are too well versed in 16:9, 4:3 and the many other standard aspect ratios in use in the film and broadcast industries, looking at them through the lens of retro computer gaming will be a breath of fresh air. For those who are new to anything that’s not widescreen 16:9 this is a great intro to a topic of fundamental importance for anyone dealing with video.
The aspect ratio of a video is a way of describing how wide it is compared to its height. This can be done by an actual ratio of width:height or displayed more mathematically as a decimal such as 1.778 in the case of 16:9 widescreen. The video discusses how old CRTs display video, their use of analogue dials that changed the width and height of the image.
In today’s world, pixels tend to be square so those encountering any pixels which aren’t square tend to work in archiving and preservation. But the reality today is that with so many second screen devices, there are all sorts of resolutions and a variety of aspect ratios. As people working in media and entertainment, we have to understand the impact on the size and shape of the video when displaying it on different screens. This video shows the impacts vividly using figurines from Doom and comparing them with the in-game graphics from Doom before then looking at aspect ratios across the SNES, Amiga, Atari ST as well as IBM DOS.
There are many video fundamentals in today’s video looking at how we see light and how we can represent it in a video signal. Following on from last week’s look at analogue 525-line video we take a deeper dive in to light and colour.
The video starts by examining how white light can be split into colours, primaries, and how these can be re-combined in different amounts to create different colours. It then moves on to examining how the proportion of colours which create ‘white’ light isn’t as even as you might imagine. This allows us to understand how to create brighter and dimmer light which is called the luminance. We’re introduced to the CIE 2d and 3d colour graphs helping us to understand colour space and colour volume
Modern video, even if analogue, is acquired with red, green and blue as separate signals. This means if we want a grey-scale video signal, i.e. luminance only, we need to combine using the proportions discussed earlier. This biased version of luminance is what is called ‘luma’ explains the video from the Displaced Gamers YouTube Channel.
On top of human perception, much of the 20th century was dominated by CRT (Cathode Ray Tube) TVs, which don’t respond linearly to electrical voltage, meaning if you double the voltage, the brightness doesn’t necessary double. In order to compensate for that, ‘gamma correction’ is applied on acquisition so that playback on a CRT produces a linear response.
Pleasantly, an oscillator is wheeled out next looking at a real analogue video waveform demonstrating the shape of not only the sync pulses but the luminance waveform itself and how the on-screen rendition would be seen on a TV. The video then finishes with a brief look at colour addition NTSC, PAL, SECAM signals. A prelude, perhaps, to a future video.
With an enjoyable retro feel, this accessible video on understanding how analogue video works is useful for those who have to work with SDI rasters, interlaced video, black and burst, subtitles and more. It’ll remind those of us who once knew, a few things since forgotten and is an enjoyable primer on the topic for anyone coming in fresh.
Displaced Gamers is a YouTube channel and their focus on video games is an enjoyable addition to this video which starts by explaining why analogue 525-line video is the same as 480i. Using a slow-motion video of a CRT (Cathode Ray Tube) TV, the video explains the interlacing technique and why consoles/computers would often use 240p.
We then move on to timing looking at the time spent drawing a line of video, 52.7 microseconds, and the need for horizontal and vertical blanking. Blanking periods, the video explains are there to cover the time that the CRT TV would spend moving the electron beam from one side of the TV to the other. As this was achieved by electromagnets, while these were changing their magnetic level, and hence the position of the beam, the beam would need to be turned off – blanked.
The importance of these housekeeping manoeuvres for older computers was that this was time they could use to perform calculations, free from the task of writing data in to the video buffer. But this was not just useful for computers, broadcasters could use some of the blanking to insert data – and they still do. We see in this video a VHS video played with the blanking clearly visible and the data lines flashing away.
For those who work with this technology still, for those who like history, for those who are intellectually curious and for those who like reminiscing, this is an enjoyable video and ideal for sharing with colleagues.
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