Numeric camera

A numeric camera is an apparatus of recording of images animated and sound on a numerical support.

Captures and Treatments

Images

The luminous rays (composed of photons), resulting from the filmed scene (image) pass through an objective optical then will strike a sensitive sensor CCC or CMOS.
Les received photons creates a load on the level of the pixels of the sensor and thus constitutes a memory of image.
Chaque pixel is thus in charge of still analogical way on this level.
Un electronic system allows " vider" regularly the analogical loads of all the pixels of the sensor and transforms them into digitized values thus constituting the digital image. This one-way circuit treats image by image with regular intervals, 24,25,29.97,30 times a second following the adjustment of the camera. It creates a serial flow numerical bound for the digital recorder with Technologie Laser (recording on DVD) or with magnetic technology (recording on cassette FD or Hi8 for the D8 format, or on hard drive).

Sounds

The sounds are captured by Microphone S connected to an equalizing network also ensuring digitalization by sampling. The circuit produces another numerical flow which is recorded at the same time as the images.

The techniques of Multiplexing of the audio stream and the video stream differ according to the standards.

Format amateur

  • DIGITAL 8
  • Mini FD
  • DVD

DIGITAL 8

Standard created by Sony to be compatible with the old analogical cassettes.

Mini FD

  • most widespread on the market, equips the numeric cameras.

  • maximum Capacity of 25 Mb/s allowing the recording of vidéos formats FD (720x576) and HDV (1280x720 and 1440x1080)

DVD

  • the Camescope DVD makes it possible to record the video sequences filmed on DVD. However it is about DVD 8 cm in diameter contrary to the normal DVD of 12 cm. Each DVD thus makes it possible to record up to 30 minutes of video to the format MPEG-2 with a definition of 704 X 576 pixels, slightly lower than that of a band FD (720x576).
  • Once recorded, the film perhaps directly read on a reader DVD of living room, a computer PC or Mac and even a PlayStation 2 for example.
  • This format was created by Hitachi.

Professional format

HDV

  • the HDV is a format of digital video high-definition which consists in compressing it video and the audio in MPEG before recording it on a tape FD. The result of this compression makes that it is possible to record a signal high-definition of the 720p type or 1080i without needing to increase the flow, which remains to the maximum with 25Mb/s (flow of the FD, therefore).

This new format makes it possible to choose between various standards at the time of the recording. It is thus possible to record in 720/60p, 720/30p, 720/50p, 720/25p but also in 1080/60i or 1080/50i. Concretely that makes it possible to record an image reaching a resolution of 1280x720 pixels in progressive mode or 1440x1080 in interlaced mode, against 720x576 pixels in general format FD. These two formats have a report/ratio of aspect 16/9 ème.

  • video

    It is compressed in MPEG-2, with a sampling color 4:2: 0 and a quantification on 8 bits.

  • the audio is compressed in MPEG-1 Layer II with 48kHZ/16bits, on two channels (stereo).
The whole thus forwards without problem via a traditional Firewire interface.

This format at the relatively low cost constitutes a serious alternative to the professional formats.

Uses: productions with small budget, short films, documentary, films amateurs HD,…

Assembly of the images

  • the development of data processing made it possible to execute the assembly of images and sound in virtual assembly on computer.

  • As a preliminary, the images are recopied since the support of catches of sights via the catch Firewire or IEEE 1394 towards the hard drive of the computer.

  • Then, the software of assembly “will virtually assemble” the sequences chosen with the possibility of corrections and special effects.

  • Lastly, the export of the finished “assembly” can be done towards a videotape, CD, a DVD or in formats compatible with the Web.

See too

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