GB2247336A

GB2247336A - Improvements relating to sound and video recording and reproducing systems

Info

Publication number: GB2247336A
Application number: GB9113266A
Authority: GB
Inventors: Phillip James Kroll
Original assignee: Individual
Current assignee: Individual
Priority date: 1990-06-19
Filing date: 1991-06-19
Publication date: 1992-02-26
Also published as: GB9113266D0; GB9013654D0

Abstract

A sound recording and reproducing system operates with a solid state memory device and with no moving parts. For reproduction, a processor extracts digital information in an ordered sequences from the device. This is converted to analogue form and then into audible sound. For recording, the analogue input is digitized and stored in the memory by the processor. <IMAGE>

Description

ImProvements relations to sound and video recording and reproducing systems This invention relates to sound or video recording and reproducing systems. For convenience, reference will only be made to sound versions, but it will be understood that the same principles apply to video versions.

Historically, recording and reproducing sound has always involved moving parts. The gramophone developed from cylinders to discs, with a needle co-operating with a groove to give mechanical vibrations translatable into sound. Tape recorders have the tape moving past a recording/playback head from one rotating reel to another. This movement is of course still necessary with Digital Audio Tape (DAT), recently developed. More recently, compact discs (CDs) with digital information have become widespread, the rotating discs being "ready by a laser beam. While the quality of sound reproduction has vastly increased, and while the size of the equipment needed has significantly decreased, the physical movement of the recording medium is a constraint on further progress.Also, unlike tape, it is not possible to make a recording on a CD other than under elaborate factory conditions, and a CD player is not truly portable, since the laser recovering the digital information tends to be disturbed if the equipment is on the move, leading to interruptions and "jumps".

There has been a recent innovation called the "music card system". It requires a mathematical synthesis to store and recover the audio signal from a credit card type digital memory. It has considerable disadvantages, one being that there is loss of integrity of the original audio sound as the synthesised reprocessing leads to undesirable wave form distortions. Also, when transferring an existing digital sound track master, this needs to be reprocessed, further deteriorating the original signal. True portability is lost as it requires a synthesizer to interpret music information code in a semiconductor memory.

It is the aim of this invention to provide simple recording and playback equipment, without moving parts, with the quality and advantages of modern CD technology, and yet with few if any of its disadvantages. Indeed it should be compatible with current industry standards, and usable with existing digital recording masters.

According to one aspect of the present invention there is provided a sound reproducing system comprising a processor with a digital signal output, means for accepting a solid state memory device, control and supervisory means governing the processor for the latter to extract digital information in an ordered sequence from a memory device in said accepting means, means for converting the digital signal into an analogue signal, and means for transforming that analogue signal into audible sound.

According to another aspect of the present invention there is provided a sound recording system comprising a processor with a digital signal input, means for accepting a solid state memory device, and control and supervisory means governing the processor for the latter to insert digital information in an ordered sequence into a memory device in said accepting means.

Generally, these systems will be combined in a single unit, the processor, control and supervisory means and the accepting means being common to both systems. Such a combined system can therefore record and reproduce, separately or simultaneously, if required.

When recording, the input may already be in digital form, for example when using a master digital tape or discs. However, the input may be "live" or at least in analogue form, in which case an analogue-digital converter will be provided to pass on the input to the processor in the required form.

The memory devices may take various forms, the accepting means of course being adapted to match. It is presently envisaged that they should be card-like and insertable into a slot to register with recording and/or read-out means. A digital recording of a piece of music contains an enormous number of bytes and w operating on a scale where the entire unit, apart perhaps from the actual sound producing means, may be comparable to a pocket calculator, a current state-of-the-art card memory might hold sufficient information for about a minute of playing time. However, it is confidently predicted that even more compact memory devices with vastly greater capacity than at present will be developed in the near future, and so it is justifiable to envisage playing times comparable to those of discs in due course.Meanwhile compromises can be made with stacks of memory cards and unit sizes larger than eventually intended.

Currently, very high standards are set for memory devices; a single fault in one cell among millions can lead to serious if not calamitous malfunction or misinformation.

Therefore there is a very high rejection rate when testing after manufacture. As more capacity is introduced on ever smaller scales, this problem will increase. However, for the present system such slightly faulty devices will be acceptable. The processor can be programmed so that, if no information is forthcoming from a cell, it will use the immediately preceding byte again and then continue as before. This will maintain continuity and will normally not be detectable by the human ear. Thus relatively cheap, slightly imperfect memory devices can be used by adopting this "concealment processing".

For a better understanding of the invention, one embodiment will now be described, by way of example, with reference to the accompanying drawing, in which the single figure is a block circuit diagram of a sound recording and reproducing system.

The heart of the system is an audio processor 1 adapted to transform digital input signals into data appropriate for writing into a memory 2, preferably a RAM in card form as mentioned above. It will also be capable of reading that data and providing a digital output identical to the original input. The processor 1 is governed by a CPU and supervisory circuit 3 with a control panel 4 for the user.

The digital input to the processor 1 may be by bus 5 into which is fed a stream of digital information, for example from a CD or other digital audio format.

Alternatively, if the sound to be recorded is still in analogue form, an A/D converter 6 transforms it to digital signals applied to the processor 1 via bus 7.

At the output, there is a D/A converter 8 t o transform the digital signals into analogue form which, after suitable amplification in unit 9, can drive headphones 10 or other sound producing devices.

The RAM 2 will of course be blank for recording.

However, the system may not always be required to do this and it is envisaged that the user will be able to buy prerecorded cards or other memory devices in much the same way as he currently buys discs or tapes. In that case, nonvolatile memory aevices will be used, such as maskedprogrammed ROMs or EPROMs.

Claims

1. A sound reproducing system comprising a processor with a digital signal output, means for accepting a solid state memory device, control and supervisory means governing the processor for the latter to extract digital information in an ordered sequence from a memory device in said accepting means, means for converting the digital signal into an analogue signal, and means for transforming that analogue signal into audible sound.

2. A sound recording system comprising a processor with a digital signal input, means for accepting a solid state memory device, and control and supervisory means governing the processor for the latter to insert digital information in an ordered sequence into a memory device in said accepting means.

3. A sound reproducing and recording system comprising a system as claimed in claims 1 and 2, with the processor, the accepting means and the control and supervisory means in common.

4. A system as claimed in claim 2 OL 3, and further comprising an analogue-digital convertor to provide the input to said processor.

5. A system as claimed in any preceding claim, wherein the accepting means is adapted to receive a cardlike memory device in a slot.

6. A system as claimed in claim 1 or 3 or claim 4 or 5 as appendant to claim 1 or 3, wherein the processing means is adapted and programmed to react to ta missing byte of information from the memory device by using the byte immediately preceding in the ordered sequence.