Video DIGITAL

History

Format FD was developed by a broad consortium, gathering companies as Matsushita (which has Panasonic), Philips, Sony, Thomson, joined by Hitachi, JVC, Mitsubishi, Sanyo, Sharp and Toshiba but also Apple and IBM, is on the whole more than one about fifty companies. This historical industrial alliance in the world of the electronic was linked to define the specifications of the new generation of Magnétoscope S general public.

Video

The image is of standard resolution of 720 X 576 pixels distributed out of two screens compressed in JPEG, the report/ratio of the image is 1.25:1, with a horizontal resolution of 500 lines, a report/ratio S/B (Signal-to-noise) of 54 dB and a Band-width Chrominance of 14 MHz, the FD offers performances quite higher than those of the formats Analogique S Hi-8 or S-VHS.

Structure of sampling

The FD is a format in components Numérique S (i.e. the signals of brightness, of differential of Bleu and differential of Rouge are treated separately). In the systems with 625 lines (STAKE, SECAM), sampling is of type, i.e. a line on two does not comprise information of Couleur S. In the systems with 525 lines (NTSC), it was selected a structure of sampling of the type. This choice is explained by the fact why the systems with 525 lines being already rather weak of vertical resolution, would have rather badly agreed to be amputees of half of their points of chrominance into vertical.

The FD using a structure of sampling 4:1: 1 in NTSC (or 4:2: 0 in STAKE), that reduce the quantity of stored colors - a problem which does not exist for an analogical format the such Betacam SP which in is made more faithful colors and also has a good performance under conditions of weak lighting (see also the numerical successors of Betacam SP: the Betacam SX and the numerical Betacam).

The structure of sampling of the FD is also one of the reasons for which one avoids using it in applications such as the chroma-key.

Quantification

The quantification of image FD is made on eight bits per layer. Thus, each layer R, V and B are suitable for code 2⁸ (that is to say 256) levels including 220 useful. The mixture of these three layers theoretically makes it possible the FD to code 220 ³ (that is to say 10.648.000) different colors. This rate of quantification makes it possible to obtain signal-to-noise Rapport a rather good (74dB theoretical), but it limits the possibilities of calibration.

Compression

The compression which uses the tools of MJPEG: JPEG and MPEG is carried out according to the contents of the image in intra-screen or intra-image. That to take account, when they exist, of the redundancies between the two screens of an image and to obtain a better effectiveness of compression. To in no case, it is not taken account of the temporal redundancy between the images, each one of them being coded separately and depending on no other what allows an assembly except for the image. Initial flow of the video signal 4:2: 0 or 4:1: 1 is of 125 Mbits/s. It is reduced, after compression with 25Mbits/s from where a compression ratio about 5:1.

Audio

Format FD, can treat 4 sampled tracks with 32 Khz and coded in 12 bits, or 2 tracks in 48 Khz and coded on 16 bits.

Flow

The recorded total flow (video + audio + auxiliary signals) borders the 41,85 Mbits/s.

Formats and cassettes

There exist various kinds of cassettes to format FD. Certain cassettes are equipped with a small chip memory making it possible to preserve a true catalog of the recorded sequences and still images, with data of index such as the date or the hour of recording, but also of the relative informations to the parameters of the camera during turning such as the opening of the diaphragm or the Speed of obturation. This chip can be used only with cameras which have this functionality.

FD :
Cassettes FD (size " L") measure 120 X roughly 90 X 12 mm and can contain up to 4,6 hours of numerical videos (either 6,9 hours in mode Long Play).

MiniDV :
The cassettes MiniDV (size " S") measure 65 X roughly 48 X 12 mm and are available of versions 30 min. (that is to say 45 min. in mode Long Play), 60 min. (90 min. in LP) and 80 min. (120 min. in LP).

DVCAM (developed by Sony) :
It is about the “professional” version of the FD. DVCAM positions, today, more in the institutional sector that professional. Indeed, such a narrow band (1/4") is not adapted to the difficult conditions of turning like to the intensive requests in assembly.

Cassettes DVCAM are proposed in two sizes which are the same ones as out of FD. The small one (S) which offers durations of 12,22,32 and 40 minutes, and the large one (L) which makes it possible to reach the 64,94,124 and 184 minutes.

DVCPRO (developed by Panasonic) :
Cassettes DVCPRO make it possible to record 66 min. ata rate of 25 Mbit/s . These cassettes are also usable in mode DVCPRO50, but as the speed of recording is then doubled, the duration of recording is some divided by two (33 min.), which is indicated by the two figures " 66/33" who are reproduced on these cassettes. Cassettes DVCPRO are of size M (size of the hand).

DVCPRO50 (developed by Panasonic in 1998) :
The DVCPRO50 doubles the speed of recording of cassettes DVCPRO and combines two codecs FD in parallel to record digital video ata rate of 50 Mbit/s .

DVCPRO HD (developed by Panasonic in 2000) :
DVCPRO HD further increases the speed of the cassette and combines four codecs FD in parallel to reach 100 Mbit/s . Cassettes DVCPRO HD are of size XL.

There exist Sony readers being able to read different type of format (MiniDV, FD, DVCAM, DVCPRO…).

Digital8 :
Digital8 also uses codec FD, but records on cassettes Video Hi8. Considering the cassettes Video8 and Video Hi8 had a great success in the past, Digital8 was conceived for the consumers as a transition between the analogical one and the numerical one. The video and audio quality of Digital8 is comparable with that of the FD.

Connector FD

There exist two type of connectors. Those are used to transfer the information which was recorded under digital form on the silver support with format FD. Its connectors play only the part of transport in order to obtain a video file FD of the type 1 or 2. Certain video cameras having of the connectors S audio VHS/rca step thru in entry make it possible to digitize the analogical signals out of FD. Certain video cameras read/digitize the infos of K7 8mm Hi8 towards exit FD. Canopus markets a converter A/N for analogical signal by a pair of connector (2RCA video audio/1S VHS).

Software FD

Any software of video edition supports capture FD. Some are specialized FD like scenalyzer or Kino (cf Kino).

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