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Creating Video

What...format_videotape.png

Digital video consists of separate video and audio bitstreams. Each bitstream is encoded and decoded using an appropriate codec algorithm and wrapped into a 'wrapper' (or container) file format. This 'wrapper' will also contain technical metadata and, possibly, some descriptive metadata also.

Why...

When creating digital video it is important to note that the choice of frame size (resolution), aspect ratio, sampling rate, bit depth and frame rate, as well as the selection of compressed (lossy or lossless) or uncompressed codecs and wrapper file formats, all play a part in determining the quality of the video. Focussing on your end requirements will help you to make a decision on the quality of video needed.

Unfortunately, there is no one agreed standard for digital video. Ideally video would be stored uncompressed but it is recognised that some form of compression (lossless or lossy) will be required when producing digital video. If you are likely to deposit with an archive such as the Modern Records Centre then, as a general rule, the higher quality the better.

How...

Processing or converting video from a video camera

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  • In general, larger frame sizes (the pixel array in height and width) are recommended over smaller ones. 1920 x 1080 (1080p) is a good minimum frame size to use.
  • Set the aspect ratio (the ratio of the width of the frame to the height) to the ratio that best serves your purposes. 16:9 is most common for HD and widescreen video, whereas 4:3 is also widely used.
  • Create your video at a minimum data rate of 25mbps.
  • Select a frame rate that is suitable for the type of recording you are doing; higher frame rates are useful for capturing detail in fast-moving action, though it's worth pointing out that human perception tops out at around 75 frames-per-second (fps). In Europe, 25 fps is most common.
  • If you are able to; set the audio sample rate at 48000 KHz.
  • Save your video using the appropriate codecs and wrapper format. If submitting to an archive such as the Modern Records Centre then:
    • If you have the ability to record using a lossless codec such as FFV1 (within a Matroska (.mkv) or Microsoft Audio Video Interleaved (.avi) wrapper) or Motion JPEG2000, then that is ideal.
    • However, consumer cameras often encode video using either a form of H.264 (AVCHD for example) with LPCM or AAC audio encoding, MPEG-2 with either LPCM or AAC audio encoding or DV encoding with LPCM audio encoding. It is worth noting that these involve some level of 'lossy' compression meaning that once a video file is processed into these forms the original images at full quality cannot be regenerated from the compressed version. (Moreover, each time lossy compression is applied, more quality is lost). Wrapper format options available may include Apple Quicktime movie (.mov), Microsoft Audio Video Interleaved (.avi) and MPEG-4 (.mp4).
    • If required create a smaller video file for sharing and access: H.264 encoded video with AAC encoded audio, within a MPEG-4 wrapper (.mp4) is suitable for this purpose.

Digitising video

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  • Select a framesize (resolution) that is 100% of the original.
  • Maintain the original aspect ratio.
  • Digitise your video at a minimum data rate of 25mbps.
  • Maintain the original frame rate. For European video this will likely be 25 fps.
  • If possible, set the video colour sample ratio (the ratio of luma (Y′) samples to each colour difference sample (CB and CR)) at 4:2:2 and colour bit depth (the number of bits used per sample) at 24 bits (also known as Truecolor).
  • If you are able to, set the audio sample rate at 48000 KHz.
  • Save your video using the appropriate codecs and wrapper format. If submitting to an archive such as the Modern Records Centre then:
    • The use of lossless codecs such as FFV1 (within a Matroska (.mkv) or Microsoft Audio Interleaved (.avi) wrapper) or Motion JPEG 2000 are best, making use of LPCM audio encoding.
    • However, you may not have the tools and resources to make use of lossless codecs and therefore MPEG-2 (.mpg), using intraframe (where each picture is encoded independently, without reference to neighbouring frames), within a Microsoft Audio Interleaved (.avi) or Apple Quicktime (.mov) wrapper would suffice, making use of LPCM audio encoding.
  • If required create a smaller video file for sharing and access: H.264 encoded video with AAC encoded audio, within a MPEG-4 wrapper (.mp4) is suitable for this purpose.