Classifications

• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
  • H04N5/00—Details of television systems
  • H04N5/76—Television signal recording
  • H04N5/91—Television signal processing therefor
  • H04N5/92—Transformation of the television signal for recording, e.g. modulation, frequency changing; Inverse transformation for playback
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
  • H04N5/00—Details of television systems
  • H04N5/76—Television signal recording
  • H04N5/91—Television signal processing therefor
  • H04N5/93—Regeneration of the television signal or of selected parts thereof

Definitions

• the present invention relates to a magnetic medium containing video information intended to be played at a fast speed different from the nominal recording speed. It also relates to a device for reading media at fast speed according to the invention and to a device for writing video information on blank magnetic media so as to constitute media according to the invention.
• the video information is recorded in the form of tracks. This information is read by scrolling the strip in front of the read heads.
• the tracks are generally arranged obliquely to the direction defined by the running of the strip, so as to increase the density of information.
• actuators positioned on the drum which drives the heads, are deformed under the effect of a control voltage, they thus allow the read heads to be moved so as to follow the tracks when the strip runs.
• the subject of the present invention is a magnetic medium containing video information recorded in the form of tracks, said information being intended to be read either at nominal recording speed, or at a speed different from said nominal speed, characterized in that the tracks are located in two distinct zones, a first zone containing the tracks intended to be read at the nominal speed and a second zone containing the tracks intended to be read at a speed different from the nominal speed, said tracks intended to be read at a speed different from nominal speed containing information compressed from video images.
• the invention also relates to reading devices and writing devices for magnetic media according to the invention.
• the invention also relates to video recorders containing reading and or writing devices according to the invention.
• FIG. 1 shows the method of reading, at nominal speed, information constituting the video image according to the prior art
• FIG. 3 shows how the information is stored on a magnetic tape in order to perform a reading according to the preferred embodiment of the invention
• Figure 4 shows the device for reading information when it is stored as described in Figure 3;
• FIG. 6 shows the device for reading information when it is stored as described in Figures 5A and 5B;
• FIG. 7 shows the information writing device to obtain a support such as that described in Figure 3;
• FIG. 8 shows the information writing device to obtain a support such as that described in Figures 5A and 5B.
• FIG. 1 represents the method of reading at nominal speed the information constituting the video image according to the prior art.
• a magnetic strip 1 contains a set of rectilinear tracks P. Each track has a width 1. For professional video recorders, this width 1 is generally between 40 and 70 microns.
• tracks P depends on the type of format used. It is thus known to those skilled in the art that a frame of the image to be reproduced is contained in two successive tracks according to the beta format in force. currently.
• One track contains the chrominance signal and the other the luminance signal.
• the tracks P are arranged obliquely. They are inclined at a certain angle relative to the direction defined by the running of the strip, the nominal running speed of which is v n .
• the drum T on which one or more read heads are arranged is oriented so that these follow the tracks.
• This drum is in the form of a cylinder of circular cross section.
• D. rotates at constant angular speed ⁇ o around the xy axis perpendicular to said section and passing through the center thereof.
• FIG. 2 represents the relative trajectory of the read heads relative to the tracks during a fast speed reading according to the prior art.
• the running speed of the strip v ⁇ is much higher than the nominal speed v n .
• the trajectory followed by the read heads can be represented, for example, by the straight line D.
• the frames no longer being read in their continuity, noise bars then appear on the image At very high speeds, we arrive at l total impossibility of recognizing the sequences read.
• the speed v ⁇ j of travel of the strip has the same direction as the nominal speed v n . It is obvious to those skilled in the art that the drawbacks described above also occur in the case where the speed v_ is in the opposite direction to the nominal speed. They are even then accentuated since the inclination of the tracks is less favorable for a correct rapid reading.
• FIG. 3 represents the way in which the information is stored on the magnetic medium in order to carry out a reading according to the preferred embodiment of the invention.
• Zone A contains the information intended to reproduce the images at nominal speed. This information can be compressed or not. All techniques can be used to achieve this possible compression of images. We can cite, by way of examples, the technique of sub-sampling, dynamic compression by blocks or even cosine transformations with high quantification.
• Zone C contains the information intended to be read at high speed.
• This information is recorded on a longitudinal track L, parallel to the direction of travel of the strip.
• the longitudinal track has the advantage of allowing the trajectory of the read heads relative to the tape to be independent of the speed of the magnetic medium.
• a video image is made up of two frames T1 and T2.
• the numerical values assigned to the various parameters describing the preferred embodiment are given at indicative title. It is obvious to a person skilled in the art that other values lead to other quite feasible embodiments of the invention.
• each frame recorded on NP 12 consecutive tracks P in zone A.
• These tracks are, for example, rectilinear, mutually parallel and equidistant from each other each other.
• d be the distance longitudinally occupied by these 12 tracks.
• a value of d can be 500 microns.
• Each bit of information can be written, for example, on 0.5 micron.
• the information which can be contained on the fraction of longitudinal track L1 of length d located below the frame Tl or even on the fraction of longitudinal track L2 of the same length located below the frame T2 can therefore contain 1000 bits.
• each uncompressed complete frame is coded on 1.2 Mega bits and if one considers a compression of images carried out using a frame subsampling by a factor of 100, then a compressed frame contains 12000 bits. The distance d containing 1000 bits, it is therefore possible to code one frame out of twelve on the longitudinal track L.
• a frame can be recorded on NP consecutive tracks P of zone A (NP being any integer). It is then possible to code a frame on N on the longitudinal track L by judiciously choosing the frame sub-sampling factor.
• the compressed image allowing the search in rapid viewing can be a reduced definition image, for example a black and white image. All image compression techniques are compatible with the use of this longitudinal auxiliary track.
• FIG. 4 represents the device for reading information when it is stored on the magnetic medium according to the principle described in FIG. 3.
• the read heads symbolically represented by the device 2 are in contact with the tracks located in the area A.
• the switch 8 is positioned so that the points K and I are connected, thus allowing the information read to be sent to display circuits not shown in the figure.
• FIG. 4 represents a device for which this information is not compressed.
• the read heads can be arranged on a drum and the images can be read at different speeds from the nominal speed.
• the read heads can be arranged on piezoelectric actuators and speeds up to ⁇ 40 times the nominal speed can be achieved with the appearance of noise bars.
• the reading heads symbolically represented by the device 3 make contact with the longitudinal track of the support 1. It is preferably when one wishes to reach speeds exceeding the limits mentioned above that this reading is performed.
• the switch 8 is then such that the points K and J are connected together which makes it possible to send the information in the display circuits mentioned above.
• the information from device 3 is compressed information. It is therefore necessary that it passes through the decompression system 4 adapted to the compression used during recording.
• the device 4 comprises a first device 5 making it possible to reconstitute a complete frame from the recorded frame fraction and a second device 6 allowing a complete image to be reconstructed from the frame thus reconstituted.
• Another embodiment of the invention consists in recording the information intended to be read at high speed on the oblique tracks themselves. This information may represent only a few percent of the total video information corresponding to the image. It can be saved for all images or only for a selection of saved images, for example one in ten images.
• the zones Z1, Z2, Z3, Z4 in which this information is recorded define a straight line ⁇ and are preferably located at equal distance from each other.
• the reading at high speed takes place so that the trajectory of the read heads follows the line ⁇ .
• the zones Z1, Z2, Z3, Z4 are very close to each other: there is one zone every 5 tracks. ⁇ is obvious to those skilled in the art that said zones may be more spaced apart.
• the frame compressed by information representing 0.3% of the total frame information using compression performed by subsampling by a factor of 100 and by black and white coding. If the compressed information intended for fast reading is recorded by groups of two heads, then the reduced information must be recorded on 2 tracks of the frame, at intervals of 100 tracks, to allow reading at the desired speed.
• the overall ordering of the magnetic medium depends on the coding and format used, the width and number of the magnetic heads as well as the limit of legibility of the tracks (signal to noise ratio limit).
• FIG. 5A illustrates an example
• the information intended to be read at nominal speed can be compressed or not.
• FIG. 5B represents an example of scheduling of the zones Zi defined above. These zones define a succession of lines ⁇ having all the same direction and located at equal distance from each other.
• FIG. 6 represents the device for reading the information when it is stored in the manner described in FIGS. 5A and 5B.
• the read heads When the images are viewed at high speed, the read heads, symbolically represented by the device 2, are in contact with the oblique tracks.
• a demultiplexer 9 is positioned so that the read heads are connected to the decompression system 10 allowing the compressed information read to be reconstructed in the form of images.
• the points L and N are then connected.
• the decompression system 10 is adapted to the type of compression used during recording.
• the device 10 can be, for example, identical to the device 4 described above.
• a tilting switch system 8 is placed at the outlet of the decompression device 10 in order to send the thus reconstituted images to the display circuits.
• the points J and K are then connected and the signal is sent to display circuits not shown in the figure.
• the same read heads are in contact with the oblique tracks and the demultiplexer 9 is positioned so that the points L and M are connected.
• the signal read is transmitted to the rocker switch system 8 via the link 19.
• the rocker switch system 8 is positioned so as to send information that it receives to the display circuits not shown in the figure. Points I and K are then connected.
• signals indicating the beginning and the end of each zone Zi can be written on the magnetic medium as mentioned previously.
• the detection of the start signal makes it possible to cut the LM link; point L is then connected, for example, to a point O isolated from any contact with the display circuits.
• the detection of the end signal makes it possible to restore the LM link.
• the detection means and the means allowing the demultiplexer 9 to switch under the influence of the start and end signals are known to those skilled in the art and it is therefore unnecessary to specify them here.
• FIG. 7 represents the device for writing information when it is stored in the manner described in FIG. 3.
• the signal S representing the image to be reproduced is separated into two fractions FI and F2 by any means known to those skilled in the art and which it is unnecessary to specify here.
• the IF signal fraction is sent via the branch
• the writing heads 12 record the information on the oblique tracks of zone A.
• the signal fraction F2 it is compressed using the compressor 14 and then sent to the writing heads symbolically represented by the device 13.
• the writing heads 13 record the information on the longitudinal track of the zone C. This information is recorded, for example, so as to be distributed on the longitudinal track as has been indicated according to the preferred embodiment (cf. FIG. 3).
• the compression device 14 can, for example, consist of an inter-frame sampler 15 for selecting the useful frames, and an intra-frame sampler 16 for selecting a fraction of the frame previously sampled.
• the reading device will be separated from the writing device so as to make it possible to read the information almost simultaneously with writing ("read after write" function).
• FIG. 8 shows the device for writing information when it is stored in the manner described in FIGS. 5A and 5B.
• the signal S is sent to a signal doubler 17.
• the signal from the doubler 17 is sent via the branch B2 and the multiplexer 18 to the heads d 'writing
• the branch B2 may contain a compression circuit although FIG. 8 does not contain it.
• the signal from the doubler 17 is sent to the branch B3, which contains a compression device 14.
• the signal from the device 14 is then sent to the writing heads 20 via the multiplexer 18.
• the write heads 20 can be of the same type as the write heads 12.

Landscapes

• Engineering & Computer Science (AREA)
• Multimedia (AREA)
• Signal Processing (AREA)
• Television Signal Processing For Recording (AREA)
• Signal Processing For Digital Recording And Reproducing (AREA)

Priority Applications (2)

Applications Claiming Priority (2)

Publications (1)

Family

ID=9427887

Family Applications (1)

Country Status (4)

Cited By (1)

Citations (4)

Family Cites Families (1)

• 1992
  • 1992-03-20 FR FR9203361A patent/FR2688970A1/fr not_active Withdrawn
• 1993
  • 1993-03-19 JP JP5516333A patent/JPH07507186A/ja active Pending
  • 1993-03-19 EP EP93920542A patent/EP0631707A1/fr not_active Withdrawn
  • 1993-03-19 WO PCT/FR1993/000282 patent/WO1993019556A1/fr not_active Application Discontinuation

Patent Citations (4)

Also Published As

Similar Documents

Legal Events