Video Codecs
General
Video is increasingly used in professional event planning as a medium for information and design. This is due in part to improved processing, and ever cheaper and more powerful output devices such as video projectors and LED matrices.
A so-called video stream goes through a number of stages before it is viewed on an output device. Firstly, the data must be read from the hard disk or SSD, then copied into memory, and then unpacked by the CPU, before an unpacked stream is sent to the graphics card. Naturally, each of these stages must have the corresponding capacity to be able to play back the video stream at the highest possible quality.
This is where the so-called codecs come in. Some codecs (e.g. MPEG) involve less compression than other codecs (e.g. H264), but require more hard disk space and a faster hard drive for playback. Conversely, MPEG requires relatively little CPU computing time in comparison to highly compressed formats.
The rule of thumb: more compression = more demand on the CPU = lower bandwidth
MXWendler Recommendations
The Codec we recommend to use with MXWendler is H.264:
- 30 or 60 FPS
- External Coding
- FHD(1080p), WUXGA(1200p), UHD(2160p) are the most used resolutions. Please keep in mind that the resolution of the video you are going to render should be divisible by 16, 8 or at least 4 to avoid problems.
- Bitrate: there are multiple tutorials and online tools to calculate the perfect bitrate for different video resolutions. To give some examples for the proper bitrates for different resolutions:
- HD1080p (1920x1080), 24/25/30 fps → 8 Mbit/s
- HD1080p (1920x1080), 48/50/60 fps → 12Mbit/s
- 4K2160p (3840x2160), 24/25/30 fps → 35–45 Mbit/s
- 4K2160p (3840x2160), 48/50/60 fps → 53–68 Mbit/s
For smooth video playback, you can use e.g.
- Up to FHD (1920x1080)
- PhotoJPEG, 75% and ALAC Audio
- FHD size and beyond
- H264 Video and ALAC Audio
- Looping footage
- H264 Video with each frame set as a keyframe (GOP=1)
Framerates
Whenever framerates in different involved components do not match each other, video playback becomes jerky and starts stuttering. The framerates in question are:
- Video framerate
- MXWendler framerate
- Monitor framerate
Today the most video output devices like monitors and video beamers have a 60Hz refresh rate following the tradition of the NTSC standard. Europeans are used to 50Hz PAL framerate, so most of the video material is produced in 25 FPS ( frames per second ). This produces the following situation:
- 25FPS Video
- 25FPS MXWendler
- 60Hz Monitor
Since the monitor and MXWendler does not match, the monitor has to show every 5th image twice, which will look stuttering. A better solution would be to :
- switch the monitor to 75Hz framerate,
- 25FPS Video
- 25FPS MXWendler
- 75Hz Monitor
- Or switch video production to 30Hz framerate,
- 30/60FPS Video
- 30/60FPS MXWendler
- 60Hz Monitor
How-tos