Unit no 3 digitizing sound and video
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Unit no. 3 Digitizing Sound and Video Adolf Knoll National Library of the Czech Republic [email protected] Learning objectives After the completion of this unit the learner will be able to: Understand the digital sound and the digital video

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Unit no 3 digitizing sound and video l.jpg

Unit no. 3Digitizing Sound and Video

Adolf Knoll

National Library of the Czech Republic

[email protected]


Learning objectives l.jpg
Learning objectives

After the completion of this unit the learner will be able to:

  • Understand the digital sound and the digital video

  • Apply basic solutions both for normal use and archiving

  • Digitize correctly sound and video and make the most common products (VCD, SVCD, DVD Video, etc.)


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Digitization of analogue audio and video

  • The analogue data in audio and video domains are most often stored on these carriers:

    • Magnetic tapes, be they in reels, audio cassettes, VHS, Video 8, and others

    • Black shellac and vinyl discs

  • These media can be replayed only on appropriate replay devices (gramophone, video cassette recorder/player, video cameras, etc.)


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How to digitize them?

  • The replay device must be connected to a conversion device:

    • Sound card in the computer for audio (Line-In Connector)

    • TV card or video chip that enables the conversion of the analogue video into the digital one (built-in or USB connected to a computer, available in a digital video recorder or camera, …)

  • For data capture the software or utility must be used that enable it


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Line-In connector

of the sound card

Analogue signal

from the headphones

connector

Digitization of a vinyl disc


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Video 8 analogue

camera

USB converter

Digitization of a Video 8

analogue recording


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Audiovisual formats: MPEG

  • Motion Pictures Expert Group (MPEG) has developed several standards from which some are highly used:

  • MPEG-1 (1988) – typical application: VideoCD (VCD)

  • MPEG-2 (1994) – typical application: DVD video or Digital TV

  • MPEG-4 – typical application: DivX or Xvid movies


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Sound in MPEG

  • The sound in an MPEG video can be stored in 3 possible layers. The layer no. 3 is known separately as MP3 audio format

  • Other digital audio formats are: WAVE, WMA, OGG, MP3pro, AAC, …

  • The sound in the audio CD is uncompressed, while in the computer world the uncompressed sound – especially for archiving – is stored in the WAVE format (*.wav)

  • Most standalone players can also play MP3 audio, while some of them can play also the WMA or even AAC files


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Bitrate in audio files

  • bitrate in kbit/s

  • audio CD: 1411 kbit/s

  • MP3 CD quality: min. 128 kbit/s

  • Lower bitrate possible when our requirements are not so high and/or when we may use WMA, AAC, or other formats

  • as the space needed for storage of digital audio is not critical today, we should avoid lower bitrates


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MPEG-1 in VideoCD

  • VCD is playable on standalone players

  • VCD legal settings:

    • bitrate: 1140 kbit/s

    • sound: 224 kbit/s in MPEG-1 layer 2

    • still image resolution: 352x288 pixels in PAL, 352x240in NTSC

    • 25 frames/s in PAL, 23.976 frames/s in NTSC VideoCD is a product that has a firm structure.

  • One CD can contain ca. 70 minutes of VHS-like video quality


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MPEG-2 in DVD video

  • DVD video that is playable on standalone players

  • Video DVD most typical legal settings:

    • bitrate: variable from 2.4 up to 9.6 mbit/s

    • sound: 192 kbit/s and more in MPEG layer 2 or PCM (uncompressed), AAC

    • still image resolution: 720x576 pixels in PAL

    • 25 frames/s in PAL

  • DVD video is a product that has a firm structure, it consists if video objects (VOB). One DVD can contain from ca. 60 minutes (high quality) to several hours of video (lower quality)


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MPEG-2 in SuperVideoCD

  • SVCD is playable on standalone players

  • SVCD legal settings:

    • bitrate: max. 2600 kbit/s

    • sound: 32 - 384 kbit/s in MPEG layer 2

    • still image resolution: 480x576 pixels in PAL, 480x480 NTSC

    • 25 frames/s in PAL, 29,97 frames/s in NTSC

  • SVCD is a product that has a firm structure. One SVCD can contain ca. 35 or more minutes of video


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VCD – MPEG1

Comparison of image resolution in typical optical disc video products

SVCD – MPEG2

DVD – MPEG2


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MPEG-4

  • Lower variable bitrate with comparably same quality as in MPEG-2 (approx. 780 kbit/s gives good results)

  • Can be combined with sound in various formats, but most typically MP3

  • Used mostly as DivX or Xvid approaches to encode MPEG-4, but possible also other ones, as e.g. NeroDigital

  • The video and audio parameters can be various, but some profiles are used the coimpatibility with standalone devices, e.g. the Theatre Profile ensures the videos can be replayed on standalone DVD players (most of them can play also MPEG-4)


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MPEG in computers

  • *.mpg/mpeg – it does not say whether it is MPEG 1 or 2

  • MPEG-4 is usually packed in *.avi; if it is made as NeroDigital then packed as *.mp4

  • AVI format (Audio-Video Interleave) can contain a large variety of video and audio formats (it must be always set up appropriately) or it can be uncompressed (very large files)

  • From other formats, most used is the Microsoft WMA


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What to use: software

  • Audiograbber (freeware at http://www.audiograbber.com-us.net): it enables the Line-In recording of analogue sound

  • Video converters come usually with basic software, most typically they convert into MPEG-2

  • DVD authoring: the low cost NERO Premium (http://www.nero.com) is a good solution

  • For MPEG-4, the Xvid (http://www.xvid.org) authoring is based on freeware, while the for DivX (http://www.divx.com) encoding, the encoder must be purchased

  • For work with Xvid (but not only), you may use the free Auto Gordian Knot software(http://www.autogk.me.uk)


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What to use: formats and parameters

  • For audio use *.wav whenever possible and MP3 with rich bitrates for applications

  • For video convert into MPEG-2 with at least 4 mbit/s variable bitrate (mostly enough for current VHS or Video8 quality) and 224 kbit/s MPEG Layer 2 sound

  • Make all the other formats and/or products afterwards (e.g. WMA or AVI Xvid video clips for Internet or VCD, SVCD, or DVD Video) from this master file that you should preserve

  • Mind that for replay of special parameters you must have special codecs (installed pieces of software that decode/encode the files); therefore, avoid very special untypical settings


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Further information

  • MPEG website: http://www.chiariglione.org/mpeg

  • Further information for those who are about to start: http://www.videohelp.com/


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