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VIDEO4Technical / WhatFormatIsTheVideoFile

What format is the video file

There are 3 components to the video file that is recorded by the VIDEO4:

1. The incoming video is encoded as MPEG2 video stream at D1 or wide-screen D1 resolution. This is exactly the same format and resolution as a DVD. The quality that the video is encoded at is set by the “bit rate”, this is the amount of information that is stored to the memory card and is measured in bits per second (bps). The bps is configurable on the VIDEO4 between 2Mb/s (2 million bits per second or 250kBytes per second, 250kB/s) for a low quality recording, up to 12Mb/s (1.5MB/s) for very high quality. Note that if you are intending to use the DVD burn tool to write your video directly to a DVD, most DVD players only support video files up to about 6Mb/s although this figure does vary depending on the model.

The bit rate that you record at depends on a number of factors:

  • How long you want to record at, and the size of your CF card:
Clearly the higher the bit rate, the less time that you can record for on a given card
  • What the data is to be used for:
If the video is for race analysis then typically a low bit rate is used. If the video is for presentation then typically a higher bit rate is used
  • What cameras are used:
If low resolution cameras are used, there is very little benefit from recording at high bit rates
  • Download consideration:
To make use of the video data the video has to be transferred from the memory card to the PC. While the USB2 card readers that Race Technology supply are very fast, long recording at high bitrates result in very large files. This is particularly a consideration when you are using the system at the track where you want to be looking at the video/data as quickly as possible

2. The audio is recorded as an MP2 audio stream. The audio is sampled at 16bit and 48kHz. The bit rate for the audio is set for xxx. Again this was chosen to be common with DVDs. The performance of the audio in practical applications is really dominated by the microphone and making sure that it is protected from wind and isolated from vibration. Somewhat surprisingly, getting good audio is rather more difficult than getting good video in racing and automotive testing applications.

3. The video and audio data streams are combined into a single file, this is called “multiplexing”. On the VIDEO4 this multiplexing is done to MPEG1 standards. Note that this MPEG1 multiplexing is nothing to do with the standard the video is encoded to that is done using the far more modern MPEG2 standard. The multiplexing only adds header and timing information to ensure that the audio and video are correctly synchronized.

Page last modified on May 12, 2014, at 11:29 AM