GB2400248A

GB2400248A - Recording of digital audio signals

Info

Publication number: GB2400248A
Application number: GB0307423A
Authority: GB
Inventors: Anthony David King-Smith; Thomas Portenlaenger; Anthony James Palmer
Original assignee: Matsushita Electric Industrial Co Ltd
Current assignee: Panasonic Holdings Corp
Priority date: 2003-03-31
Filing date: 2003-03-31
Publication date: 2004-10-06
Anticipated expiration: 2023-03-31
Also published as: GB2400248B; GB0307423D0

Abstract

A digital audio receiver apparatus has a buffer memory for storing a portion of the received signals (rewind memory) and a further memory for storing the whole of the received signals, eg to be played back later. The user can control the relative proportions of these memories.

Description

RECORDING OF DIGITAL AUDIO SIGNALS

The present invention relates to method and apparatus for recording digital audio signals more specifically, but not exclusively, audio signals which have been broadcast.

The advent of digital television transmissions and DVD has resulted in an interest in efficient methods of recording digital signals representing video and audio. For example, US-A-4,963,995 discloses a digital recording technique which stores the recorded broadcast in a random access memory comprising the combination of a semi-conductor RAM buffer and a disc memory, permitting a desired programming segment to be immediately accessed and viewed without the time consuming fast-forward and fast-reverse tape motion required in conventional tape recorders. Various modifications to this basic technique have been disclosed in US-A5,371,551 and US-A-6,233,389 but in both cases much attention has been given to the recording of digital video signals and reliance has been placed on the combination of RAM memory with hard disc memory. The RAM memory is provided in order to permit the rewind facility which is present when utilising tape recording.

It is an object of the present invention to provide a system for recording audio signals and particularly broadcast audio signals in a relatively inexpensive and convenient fashion.

The present invention provides a digital recording system which comprises means for receiving digital audio signals, a single storage device for storing digital audio signals received by the receiving means and a control device for controlling the writing of digital audio signals into the storage means and reading of digital signals out of the single storage means.

Advantageously, the user can instruct the control device to alter the separation between rewind storage and main storage.

Preferably, the digital audio signals are stored in coded and/or compressed form and any digital signals read from the storage means are input to an audio decoding circuit prior to being output via a digital analog converter and output circuitry.

Advantageously, in the preferred embodiment, a visual display is provided to enable a user to monitor how much storage space is available for main storage and rewind storage.

In order that the present invention be more readily understood, an embodiment thereof will now be described by way of example with reference to the accompanying drawings in which: Fig 1 shows a block diagram of a conventional digital recording system; and Fig 2 shows a block diagram of a digital recording system according to the present invention.

Referring firstly to the prior art arrangement, this represents a typical conventional recorder which records broadcast signals. The apparatus comprises an antenna 1 which receives broadcast signals which have been encoded according to a desired broadcast standard. The signals are demodulated by a demodulation circuit 2 and then supplied to a first in first out (FIFO) buffer store 3, which temporarily stores a small proportion of the received signals and the output of which is fed to a decoding circuit 4. After decoding, the signal is subjected to digital to analog conversion in a converter 5 and then output by one or more output devices which in this case are shown as speakers 6.

The demodulator circuit 2, FIFO store 3, decoding circuit 4 and digital to analog converter 5 are all controlled by a CPU 8 in a manner which is well known.

If it is desired to record the digital signals received by the demodulator 2, a separate store 10 is provided which is controlled by the CPU 8. When it is desired to replay signals stored in the store 10, the CPU reads the data out of the store 10 and supplies it to the decoding circuit 4 and the output process continues as before.

The above arrangement is relatively costly in view of the fact that two different storage media are required and little or no information is available to the user regarding the amount of free storage space available. Also, the amount of storage available in the FIFO is fixed.

Turning now to the present invention, and in particular to the embodiment shown in Fig 2, the same reference numerals are used for the same parts and consequently these parts will not be further described. However, the apparatus is specifically designed to record audio signals. The originals are preferably broadcast signals received using a suitable wireless protocol but can be signals received via the Internet, for example. It will be noted that the present embodiment differs from the prior art in that the FIFO storage 3 no longer exists and now all demodulated signals are fed to the audio decoder 4 via the storage device 10 under the control of the CPU 8. Thus there is a now a single storage medium for all purposes.

Store 10 can be either built-in or could be formed by a removable storage medium such as an SD card, MMC card, memory stick or recordable mini-disk.

The storage 10 does not need to be partitioned in any way in order to achieve the dual use of semi-permanent storage and "rewind" storage. All that is required is that the CPU has instructions which enable a selectable amount of the memory to be used as the "rewind" storage. The user then has the ability to signal to CPU how much "rewind" storage is required.

In normal use, as an example, the storage 10 is RAMof a size suitable to store 30-40 minutes of coded programming. With current digital audio broadcasting standards, a 256 megabit S-DRAM would be sufficient. A user wishes to have sufficient memory available so that he or she could "rewind" and replay one song received by the apparatus. This is signalled to the CPU either by using a remote control or by pressing buttons on the apparatus. The CPU then determines how much memory needs to be used for "rewind". Since "rewind" is used for the signals received in the immediately preceding time period, in this case 3 minutes, and since with DAB one frame of audio is equal to 24 milliseconds, the CPU can simply count back the exact time required through the FIFO. In some instances it may be necessary for the CPU to allocate an appropriate number of l O addresses and note the last of these, in order to achieve the same effect..

When "rewind" and replay is requested by the user, the CPU then reads out data from within the allocated addresses. In other words, if a listener hears the start of a song and wishes to record all of it, they can "rewind" back to the start of the song, press "record" then go back to where the song is now. The entire song will then be recorded.

The above arrangement can be modified in the event that the storage 10 is contributed by a disk medium such as a recordable mini-disc or DVD-RAM.

In order to enable the user to have more control, a visual display 12 is provided which gives the user an indication of the total amount of storage, as represented by time as well as the selected amount of "rewind" storage. Also, the amount of storage utilised can be indicated.

The preferred use of the above recording apparatus is in a digital radio receiver and if the storage 10 is removable as could be the case if it were in the form of an SD card, the user could have the facility to readily alter the total amount of storage available.

While a single storage device is disclosed above, it will be appreciated that the same effect could be achieved with a number of storage devices of the same types. This would enable apparatus to be constructed with a small amount of storage which could be added to by the removable storage medium disclosed above.

Claims

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CLAIMS: 1. Audio apparatus comprising means for receiving digital audio signals, first means for temporarily storing a portion of the received signals, second means for storing the whole of the received signals, control means for controlling the first and second storing means and means for producing an audio output from the received signals, characterized in that the first and second means are of the same type.
2. Audio apparatus according to claim 1, wherein the first and second storing means are constituted by a single memory device.
3. Audio apparatus according to claim 1 or 2, wherein the control means is arranged to alter the effective size of the first storage means.
4. Audio apparatus according to claim 3, wherein the control means is arranged to receive user-input signals in order to alter the size of the first storage means.
5. Audio apparatus according to claim 1, wherein at least one of the first and second means is in the form of a removable recording medium.
6. Audio apparatus according to claim 5, wherein the removable recording medium is in the form of an SD card, memory stick or MMC card.
7. Audio apparatus according to any one of the preceding claims, wherein the audio apparatus is a digital radio receiver.