7. Production: Key Concepts Follow
By Simon Baker, Technical Director and Digital Producer at Wise Children
Output Resolution & Frame Size
This is how big your image will be native. In real terms, this is the number of pixels in each direction and is normally quoted as width by height, but you will often see only the height pixel count quoted.
For our purposes, we're only concerned with either 1080p or 720p. 1080p is an image size of 1920px x 1080px. This is what we think of as High Definition TV at a ratio of 16:9 (widescreen, as opposed to 4:3, which is what older TVs were). 1280 x 720 is another common standard and what's often to referred to as "HD ready". This is a lower quality picture but still in wide use, and better quality than watching in standard definition.
Creating the illusion of a moving image hasn't changed since it was discovered. It's ultimately a series of still images shown in quick succession to create the illusion of movement - think of those flip-books you used to have as a child. The amount of still images used in one second of film is the frame rate.
When "movie" cameras were first invented, there were no motors in them, so opening and closing the shutter was manually done by turning a lever. It turned out that the best amount of frames to give the illusion of a moving image was between 18 and 26 frames. Over the years, the standard of 24 frames per second was adopted.
There is no best frame rate to use - it all depends on what you are trying to do, and what you want your footage or broadcast to look like. 25fps is my preferred frame rate. This gives a cinematic look with a degree of motion blur that I like, although this is a personal preference.
30fps has been adapted for TV and is often preferred by sports events due to reduced motion blur. Frame rates of 60fps might be great for video gameplay or sports shot in 4K, but this is often not necessary for drama.
Please note that when your stream is broadcast from TicketCo's servers, it will be capped at 30fps.
Put simply, a 4K frame size and a high frame rate will not necessarily look best, and there's a third thing to consider...
If frame size is the size of the image, and frame rate the number of images, then bit rate defines the quality of each of those images. The higher the bit rate, the more information can be stored in each one of those pictures. Bit rate can be very important in streaming and video broadcasting, and is often overlooked.
So when thinking about cameras and mixers and streaming servers you need to consider three things:
- Frame Size
- Frame Rate
- Bit Rate
These elements each affect each other. There is no point spending loads of money on 6K cameras if your audience will ultimately be watching a stream on their smartphone over a poor 4G connection.
This whole enterprise relies on a stable network connection and fast internet. Neither should be taken for granted. In large buildings with Cat5 infrastructure and fibre quality broadband, you can be easily fooled into thinking this will be simple.
Firstly, you will need a network plan. You might be used to these if you work in sound or lighting, but if you're not, then think more along the lines
- A network for control data and maybe data transfer
- A network for the stream output
- A network for people watching the stream as it's deployed out.
Primarily, you want the network sending the stream to TicketCo to be as pure as it can be. You need the speed of connection to be unrestricted, and you need to ensure you're not tripping over any firewalls, blocking ports or quality of service issues. You'd be surprised what IT departments place on their managed routers. You need to be working closely with the IT department as they will be nervous about giving you free unrestricted access to their broadband links.
Cat5 cable length and quality can also play a part. Often, there are kilometres of cable between that socket on the facilities panel you are plugging into and the connector going into the router in the server room. There might also be a hundred terminations. Each one is a potential failure point, so be wary of assuming the building infrastructure is good to go. Quite often, the length alone means a voltage drop. I usually put a simple router at various point of the system - when in doubt, run a cable direct!