Difference between revisions of "Video Codecs"

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(Update to h264)
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== General ==
 
== General ==
  
Video is increasingly used in professional event planning and in theatre as a medium for information and design. This is due in part to improved processing, and ever cheaper and
+
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.
more powerful output devices such as video projectors and LED matrices. From a technical point of view, when being played back a video signal must always be compressed; otherwise the data rate (bandwidth) would be too high.
 
  
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 DVD, then copied into memory, and then unpacked by the CPU (Central Processing Unit), before an unpacked stream is sent to the graphics card, where it perhaps undergoes further processing. Only then can the signal be sent to the projectors. Naturally, each of these stages must have the corresponding capacity to be able to play back the video stream at the highest possible quality.  
+
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. DV) involve less compression than other codecs (e.g. H264), but require more hard disk space and a faster hard drive for playback, and thus higher bandwidth. Conversely, DV requires relatively little CPU computing time in comparison to highly
+
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.
 
compressed formats.
  
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For smooth video playback, you can use eg.
 
For smooth video playback, you can use eg.
  
* XGA Size ( 1024x768 )
+
* Up to FHD (1920x1080)
 
** PhotoJPEG, 75% and ALAC Audio
 
** PhotoJPEG, 75% and ALAC Audio
  
* HD Size and beyond
+
* FHD Size and beyond
** MPEG2 Video and MPEG3 Audio
+
** H264 Video and ALAC Audio
** h264 Video and ALAC Audio
 
  
 
* Looping footage
 
* Looping footage
** Intra-Frame codecs like eg. Cinepak
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** H264 Video with each frame set as a keyframe (GOP=1)
  
 
== Framerates ==
 
== Framerates ==
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:* Monitor framerate
 
:* Monitor framerate
  
Unfortunately 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:
+
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 Video
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:* 60Hz Monitor
 
:* 60Hz Monitor
  
Since monitor and MXWendler does not match, the monitor has to show every 5th image twice, which will look unfluent. A better solution would be
+
Since monitor and MXWendler does not match, the monitor has to show every 5th image twice, which will look stuttering. A better solution would be
  
 
* Switch monitor to 75Hz framerate
 
* Switch monitor to 75Hz framerate

Revision as of 16:50, 3 October 2019

How-tos


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 per 16, 8 or at least 4 to avoid problems.
    • Bitrate:
Macroblocks pro Examples for Videobitrate (VCL) for Profiles
Level Frame Seconds Resolution
these Levels
Baseline
Extended
Main
High
4.2 8 704 522 240 1920 × 1080 / 64
2048 × 1080 / 60
50 Mbit/s 62,5 Mbit/s
5.2 36 864 2 073 600 3840 × 2160 / 66,8
4096 × 2160 / 60
240 Mbit/s 300 Mbit/s


For smooth video playback, you can use eg.

  • 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 do not match, video playback becomes jerky and stuttering. The framerates we are talking about here 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 monitor and MXWendler does not match, the monitor has to show every 5th image twice, which will look stuttering. A better solution would be

  • Switch monitor to 75Hz framerate
    • 25FPS Video
    • 25FPS MXWendler
    • 75Hz Monitor
  • Switch video production to 30Hz framerate
    • 30/60FPS Video
    • 30/60FPS MXWendler
    • 60Hz Monitor