`
`GK-EIS-1028
`
`U.S. Application No.:
`
`International Application No.: PCT/EP98/03981
`
`International Filing Date:
`
`JUNE 30, 1998
`
`30JUNE1998
`
`Priority Date Claimed:
`
`JULY 1, 1997
`
`1 JULY1997
`
`Title of Invention:
`
`METHOD AND DEVICE FOR SIGNAL CODING
`
`Applicant(s) for (DO/EO/US): Detlef WEISE and Joerg RIMKUS
`
`English Translation
`of the SPECIFICATION
`
`IPR2016-01710
`UNIFIED EX1031
`
`
`
`...
`
`'
`
`J
`
`IN THE UNITED STATES PATENT AND TRADE MARK OFFICE
`
`VERIFICATION OF TRANSLATION
`
`I, Michael Wallace Richard Turner, Bachelor of Arts, Chartered Patent
`Attorney, European Patent Attorney, of I Horsefair Mews, Romsey,
`Hampshire 505 1 8JG, England, do hereby declare that I am conversant
`with the English and German languages and that I am a competent
`
`translator thereof;
`I verify that t he attached English translation is a true and correct
`
`tran slation made by me of the attached documents in t he German language
`of International App lication PCT/EP98/ 03981 ;
`
`I
`
`further declare that all statements made herein of my own
`
`know led ge are true and that all statements made on information and belief
`are believed to be true; and further that these statements were made w ith
`
`the knowledge t h at willful fa lse statements aod t he like so made are
`
`punishable by fine or imprisonment or both under Section 1001 of T it le 18
`
`of the United States Code and that such willful false statements may
`jeopardize the validity of the application or any patent issued thereon.
`
`MW R Turner
`
`
`
`.. ~ ..
`
`. .
`
`Corporate Computer Systems Europe GmbH
`
`Ludwigstrasse 45, 85399 Hallbergmoos
`
`Method and apparatus for encoding signals
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`5
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`The invention concerns a method of encoding signals, in particular
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`digitised audio signals, with an encoding device for encoding the signal in
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`an encoding format and a processing device for processing the encoded
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`signal.
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`10
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`Methods of that kind are known for example from European patent
`
`specification No 290 581. In that case, in the bit rate-reducing encoding of
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`audio signals which are already present in digitised form, for example 48
`
`kHz sampling frequency/16-bit resolution, psycho-acoustic phenomena of
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`the perception of audio signals are used in such a way that the original bit
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`15
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`rate of the audio signals is considerably reduced. Such methods are also
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`familiar and standardised under the heading of 'source encoding' (ISO
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`11172 and 11318).
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`With some encoding methods there is also the option of encoding the
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`signal in a given transmission or storage format in order then to be able to
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`20
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`transmit and/or store the signal. That encoding however frequently gives
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`rise to the necessity for the signals to be re-coded in regard to the
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`transmission or storage format used as the transmission channel which is
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`then actually employed or the storage device which is actually used
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`employs another encoding format. If the necessary re-coding algorithms for
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`25
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`re-coding the signal for adaptation to the actual encoding format are not
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`available, the result of this is that complete decoding of the signal into a
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`linear, non-data-reduced format and subsequent encoding to the desired
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`format have to be implemented. That frequently results in quality losses of
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`greater or lesser severity. Either that expensive path
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`is adopted or
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`30
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`adaptation is not possible.
`The object of the present invention is to provide a method of the
`
`kind set forth in the opening part of this specification, which resolves the
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`1
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`
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`above-indicated problems and in which re-coding operations, once encoding
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`has been effected, are very substantially avoided.
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`In accordance with the invention that object is attained in that, in a
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`method of the kind set forth in the opening part of this specification, the
`
`s
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`encoding format is determined in dependence on the properties of the
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`processing device.
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`With
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`the method according
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`to
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`the
`
`invention
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`it is particularly
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`advantageous that encoding is already effected at the transmission end,
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`taking account of the properties of the connected devices for subjecting the
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`10
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`signals for further processing. In other words, it is already possible in the
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`encoding procedure to take account of and use the encoding formats which
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`are necessary for the connected items of equipment. In particular by means
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`of the present method it is possible to implement encoding which is
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`adapted to the possibilities of the selected transmission channel and
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`15
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`decoding at the reception end, so that the signal can be transmitted and
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`received or decoded at the maximum possible quality.
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`Furthermore the method according to the invention makes it possible
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`in any case to avoid expensive re-coding of the encoded signal as the signal
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`is encoded from the outset in the correct format, that is to say the format
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`20 which corresponds to the connected items of equipment, for example the
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`connected storage device or the connected transmission channel. The
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`method therefore not only permits higher-quality transmission of signals
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`but also faster transmission.
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`A particularly advantageous embodiment of
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`the
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`invention
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`is
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`25
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`distinguished in that, prior to establishing the encoding algorithm, the
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`properties or the property parameters of the selected transmission and/or
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`storage and/or decoding devices are ascertained by one or more test
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`signals directed to the corresponding device. In that way by virtue of the
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`method according to the invention it is possible for the encoding format to
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`30
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`be used or the encoding algorithm to be applied to be directly adapted to
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`the devices which are actually connected in each case, such as for example
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`transmission channels, storage means or decoding devices at the reception
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`end. With the method according to the invention therefore, a person who
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`2
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`
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`_,
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`would like to transmit signals, by virtue of the test signal, no longer needs
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`to establish or make adjustments for connected items of equipment which
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`are involved, such as for example transmission channel, storage device or
`
`decoding devices at the reception end, when that person would like to
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`5
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`transmit or send signals. With the solution according to the invention
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`however it is possible, prior to the actual encoding by hand, to preset the
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`corresponding parameters for selection of the desired encoding format in
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`order for example to permit transmission even with devices which are not
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`recognised by means of the test signal. In any case therefore the method
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`10
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`according to the invention permits adaptation of the encoding format to the
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`items of equipment used.
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`If the signal to be sent is a digitised audio signal and the signal is
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`present in source-encoded form, that is to say in bit rate-reduced form, the
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`method according
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`to
`
`the
`
`invention makes
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`the
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`following possible:
`
`if
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`15
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`transmission and/or storage devices of various capacities are available,
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`then, having regard to the amount of data which is still to be transmitted
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`after bit rate-reduced encoding, it is possible to select a transmission
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`channel which enjoys appropriate capacity or a storage device which enjoys
`
`appropriate capacity. Thus for example in the case of signals of relatively
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`20
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`low quality or when the demands in terms of reception quality are relatively
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`low, that is to say with a higher level of redundancy, it is possible to adopt
`
`a transmission channel of lower capacity and thus possibly save cost.
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`The invention is used for example in regard to transmission or
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`storage of data-reduced audio signals which are present for example in the
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`25
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`formats G.711, G.722, MPEG 1/2-layer 1, 2, 3 or MPEG 4. The invention
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`can be applied to all systems, for example transformation and subband
`
`encoding methods, adaptive and non-adaptive pulse code modulation
`
`methods, with linear and non-linear quantisation, combinations thereof and
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`other audio encoding methods.
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`30
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`The invention also makes use of certain properties of such methods.
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`Typically audio signals which are to be transmitted or stored and which are
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`data-reduced require only a low transmission or storage capacity. The
`
`result of this is that audio signals can be transmitted even over narrow-
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`3
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`
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`band lines in real time. In that case the data rate of the audio signals is so
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`selected that they satisfy either the qualitative claims or the economic and
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`commercial requirements. A high data rate has a correspondingly high
`
`quality, on the other hand it also requires a larger channel or storage
`
`s
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`capacity, which in turn gives rise to higher costs. When dealing with very
`
`narrow-band
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`transmission channels,
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`if wide-band channels are not
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`available, the transmission of high-quality audio signals, that is to say
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`audio signals having large quantities of data, are implemented in an n(cid:173)
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`times real time with n > 1.
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`10
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`Therefore a particularly preferred embodiment of the invention is one
`
`in which bit rate-reduced audio signals are to be sent and a plurality of
`
`transmission channels and/or bit rates are available for transmission of the
`
`audio signals. Then, by virtue of the method a·ccording to the invention, the
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`transmission channel and/or the bit rate in the transmission of the audio
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`15
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`signals can be selected
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`in such a way that the audio signal can be
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`transmitted in real time or even faster than real time.
`
`Advantageous developments and configurations of the method
`
`according to the invention are set forth in the appendant claims.
`
`Another object of the present invention is to provide an apparatus for
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`20
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`encoding signals, which avoids the problems set forth in the opening part of
`
`this specification and in which re-coding of the signal after encoding has
`
`been effected is no longer necessary.
`
`In accordance with the invention that object is attained by an
`
`apparatus for encoding signals, having a control device which presets the
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`25
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`encoding format to be used for the encoding operation in dependence on
`
`the properties of a processing device for subsequent processing of the
`
`signals.
`
`The advantage of the apparatus according to the invention is that the
`
`encoding format takes account from the outset of further processing, that is
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`30
`
`to say for example transmission or storage of the signal. That means that
`
`the signal cannot undergo incorrect encoding in the sense that the signal is
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`encoded
`
`in an encoding
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`format which does not suit
`
`the selected
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`4
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`
`
`-·
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`transmission or further processing devices, such as for example a storage
`
`device.
`
`In a particularly preferred embodiment of the invention it is possible
`
`by means of a control device having a test signal generator which emits a
`
`s
`
`test signal, by means of which the control device establishes the properties
`
`of the connected device, thus for example the bit rate of the connected
`
`transmission channel, suitably to automatically select the encoding format
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`by means of the control device. The user therefore does not need to
`
`intervene manually in the procedure for selecting the desired encoding
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`10
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`format. That therefore advantageously affords a considerable simplification
`
`in operation. For, on the one hand there is now no need for manual setting
`
`of the encoding format and in addition the user of the apparatus is not
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`embarrassed even if that person - for example as a lay person - does not
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`have the appropriate knowledge about the transmission channel or the
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`15
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`decoding options at the
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`reception end. The
`
`invention
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`is
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`therefore
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`distinguished in particular by its user-friendliness.
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`In a further embodiment of the invention, provided at the control
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`device is a display input device which makes it possible for a user to preset
`
`an encoding format to be used. It is thus possible to select the correct
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`20
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`encoding format even when the format suiting the. selected transmission
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`device or storage device or decoding device is not known and also detection
`
`by means of the test signal is not possible. It is particularly preferred in
`
`that respect that the user can select from predetermined formats; it is
`
`however also possible for the user to completely freely preset a given
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`25
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`encoding procedure or even entirely prevent an encoding procedure.
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`Further advantageous embodiments of the apparatus according to
`
`the invention are set forth in the appendant claims.
`
`The invention will now be described in greater detail by means of an
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`embodiment with reference to the accompanying drawings in which:
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`30
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`Figure 1
`
`is a block circuit diagram of the structure at
`
`the
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`transmission end of an embodiment of the apparatus according to the
`
`invention for the encoding of signals or a possible implementation of the
`
`method according to the invention, and
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`5
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`
`
`-·
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`Figure 2 is a block circuit diagram of a decoding and storage device
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`at the reception end for further illustrating the invention.
`
`Figure 1 shows a block circuit diagram of the structure at the
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`transmission end of an installation for carrying into effect an embodiment
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`5
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`of the method according to the invention. Referring to Figure 1, a digitised
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`10
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`15
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`monophonic audio signal TE
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`is passed to one of the available encoding
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`algorithms Cl or C2, according to a switch position of a switch Sl. The
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`output signal T Ec1 or T Ec2 of the encoding algorithm stage Cl or C2
`
`respectively is passed to transmission channels Ul or U2 or a storage unit
`SP, according to a switch position of switches S2a and S2b. The signal TEci or
`TEc2 stored in the storage unit SP can be passed at a later time to one of
`the transmission channels Ul or U2. The control of the switches Sl, S2a and
`S2b regulates a control unit K in dependence on properties or parameters of
`the desired encoding format, which are set at a user interface N serving as
`
`an input/display device and/or stored in a parameter storage means M. In
`addition the control unit K can control the switches Sl, S2a and S2b
`dependence on a
`test signal previously sent to the
`lines Ul or U2
`
`in
`
`respectively or to the storage device SP. The test signal gives the control
`
`unit K the information about the properties or parameters of the channels
`
`20 Ul or U2 or the storage device SP. For signal communication between the
`
`storage device SP and the control unit K, an additional direct connection K(cid:173)
`
`SP can be made. With those items of information, the control unit K then
`
`selects the encoding format Cl or C2 corresponding to those properties or
`
`parameters, by suitably positioning the switch Sl. Thus in particular the
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`25
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`parameter bit rate of the encoding algorithm stage Cl or C2 is set by the
`
`control unit K in dependence on the parameters set at the user interface N
`
`and/or the parameters stored in the parameter storage means M and/or
`
`the necessary parameters, which are detected by the test signal, for the
`
`transmission channels Ul and U2 respectively.
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`30
`
`A user can select by means of the user interface N receiver
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`parameter sets El, E2 or E3 (not shown), using a switch (not shown) and
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`read out the data thereof, for example bit rate, transmission channel and
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`possibly also encoding algorithm, from the parameter storage means M. By
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`6
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`
`
`-·
`
`means of the user interface N the user can also alter and store or override
`
`the parameters of the receiver parameter sets so that the parameters of
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`the interface N and not those of the parameter storage means are used.
`
`That may be necessary by virtue of the current transmission and/or storage
`
`s
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`to be implemented.
`
`To illustrate the invention Figure 2 shows a block circuit diagram of a
`
`device at the transmission end. In regard to the parameters used there this
`
`device corresponds to the receiver parameter set El from Figure 1. The
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`output signal TAci of the transmission channel Ul is passed to the decoding
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`10
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`algorithm stage Dl and there decoded in accordance with the decoding
`
`specification. Alternatively or simultaneously the output signal TAci of the
`
`transmission channel Ul can also be passed to the storage unit SP. The
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`output signal of the decoding algorithm stage TA is a digitised monophonic
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`audio signal.
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`15
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`By virtue of the method according to the invention the decoding
`
`algorithm of the decoding algorithm stage Dl was established for example
`
`by the control unit K by a test signal sent to the decoding algorithm stage.
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`Encoding (see Figure 1) was therefore implemented in a mode adapted to
`
`the detected decoding algorithm stage. Decoding is thus effected by Dl
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`20 without any problems, at the reception end.
`
`The invention further concerns firstly a recording, processing and
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`transmission apparatus of a first type for the storage, processing and
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`transmission of audio signals, with an analog audio signal
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`input,
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`in
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`particular a microphone or a microphone input connection, a converting
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`25
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`device for processing analog audio signals to digital audio data and a
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`storage medium for the storage of the digital audio data; secondly a
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`recording, processing and transmission apparatus of a second type for the
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`storage, processing and
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`transmission of audio data, with an
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`input
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`connection for digital audio data and a storage medium for the storage of
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`30
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`the digital audio data; and thirdly a reproduction apparatus for the
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`reproduction of audio signals with a headset or headset connection, a
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`converting device for processing digital audio data to analog audio signals
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`and a storage medium for the storage of the digital audio data.
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`7
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`
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`.·
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`Apparatuses of that kind, in which a·nalog signals are digitised and
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`then stored on a digital storage medium are known. Such apparatuses can
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`generally also record audio data which are fed in digitally, directly on to the
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`digital storage medium. Such apparatuses are also known, in which the
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`5
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`digitally stored audio data can be
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`reproduced after digital/analog
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`conversion by way of an analog audio output, in particular a headset or a
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`headset connection.
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`Apparatuses of that kind are used with different functional extents
`
`for example in the hi-fi sector. Depending on the equipment involved in the
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`10
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`apparatus hi-fi devices of that kind are suitable for recording, processing
`
`and/or reproducing the audio signals .. Different storage media are required,
`
`depending on the recording standard used. When using the DAT-standard
`
`(Digital Audio Tape) and the DCC-standard (Digital Compact Cassette) the
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`storage medium for storage of the digital and data-reduced audio data is a
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`15 magnetic tape. In the case of a further standard, the MD (Mini-Disk),
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`magneto-optical storage disks as storage media are used for storage of the
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`digital audio data which are data-reduced from psycho-acoustic points of
`
`view.
`
`With
`
`the
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`recording, processing,
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`transmission and
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`reproduction
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`20
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`apparatuses of the general kind set forth, the audio signals are stored in
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`digitised form on the storage medium and can be processed and/or handled
`
`by playback with simultaneously fresh recording by means of a further
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`apparatus. The storage medium on which the audio data are stored can be
`
`removed from the apparatus and kept for later use if the stored audio data
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`25
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`are not required for the time being. Fresh audio data can be stored by
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`erasing and playing over audio data which are no longer required or using a
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`storage medium which has not yet been used.
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`For the situation where the stored audio data are required at another
`
`location, the situation is mainly that the storage medium such as for
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`30
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`example the cassette or disk is taken to the desired location. When it has
`
`arrived there the storage medium is inserted into a suitable reproduction
`
`apparatus so that the stored digital audio data can be processed or
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`reproduced after digital/analog conversion as analog audio signals.
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`8
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`
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`The object of this further invention is to develop the apparatuses of
`
`the general kind set forth, in such a way that in particular processing and
`
`transmission of audio data are accelerated and operation of the apparatus
`
`is facilitated.
`In the recording, processing and transmission apparatuses and in the
`
`s
`
`reproduction apparatus of the kind set forth above, in accordance with the
`
`invention that object is attained in that the storage medium is intended for
`
`constantly remaining in the respective apparatus and the apparatus has a
`
`respective
`
`interface
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`for transmission of the digital audio data
`
`to a
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`10
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`processing device which is external to the apparatus.
`
`The advantages of this invention are in particular that the audio data
`
`can be transmitted by way of the interface in a simple fashion. In that
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`respect, in a first step the digital audio data can be transmitted to a
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`computer in order then in a second step to be communicated by way of a
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`15
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`data remote transmission line or by means of an electronic mail system to
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`locations which are further away. By virtue thereof it is advantageously no
`
`longer necessary for the storage medium itself to be transported from one
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`location to the others. The period of time from the moment of recording an
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`audio signal, for example by means of an apparatus of the first or second
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`20
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`type, to the moment of reproducing the recorded audio signal, for example
`
`by means of an apparatus of the third type, is considerably reduced. In
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`addition there is no longer the danger that the storage medium suffers
`
`damage or is lost during transportation of the audio data.
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`The design according to the invention can be carried into effect with
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`25
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`a cable-less or cabled interface.
`
`In addition the apparatus according
`
`to the invention saves on
`
`numerous precision-engineered components which permit interchange of
`
`the storage medium
`
`in
`
`the case of the known apparatuses. The
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`manufacturing cost of the apparatus is reduced by virtue of the saving on
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`30
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`the precision-engineered components. At the same time the
`
`level of
`
`reliability of the apparatus is increased as in particular the precision(cid:173)
`
`engineered components of an apparatus are the cause of failures and
`
`problems.
`
`9
`
`
`
`In a preferred embodiment the apparatus according to the invention
`
`of the first type has an analog high level input connection and/or a digital
`
`input connection for audio signals. Those connections make it possible for
`
`the apparatus according to the invention also to record, process and
`
`s
`
`transmit signals from the conventional analog or digital recording and
`
`reproducing apparatuses.
`
`In a particularly preferred embodiment, the apparatuses according to
`
`the invention of the first and second types have a converting device for
`
`processing digital audio data to analog audio data in order to permit
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`10
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`reproduction of the stored digital audio data as analog audio signals.
`
`In a desirable development _the apparatuses according
`
`to
`
`the
`
`invention have a headset or at least one headset output connection so that
`
`the stored audio data, after digital/analog conversion, can be acoustically
`
`reproduced.
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`15
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`The required storage space for storage of the digital audio data can
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`be reduced in a particularly preferred fashion by the digital audio data
`
`being converted
`
`into a data-reduced
`
`format. For
`
`that purpose
`
`the
`
`apparatuses according to the invention have a converting device for
`
`converting the digital audio data into a data-reduced format, for example in
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`20
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`accordance with the MPEG, AAC, AC3 or ATRAC-standard.
`
`The preferred embodiments described hereinafter relate both to the
`
`recording, processing and
`
`transmission apparatuses according
`
`to
`
`the
`
`invention of the first and second types and also the reproduction apparatus
`
`according to the invention.
`
`25
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`In the apparatuses according to the invention the storage medium is
`
`preferably a flash-RAM or a dynamic RAM. Further precision-engineered
`
`components are saved by virtue of using RAM-units of that kind. That
`
`means that the level of reliability of the apparatuses is further enhanced for
`
`the reasons set out above. In addition, the use of RAM units makes it
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`30
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`unnecessary to use a motor for transporting a magnetic storage tape or a
`
`magneto-optical disk so that energy can also be saved during operation.
`
`The interface for cable-less transmission of the digital audio data to a
`
`processing device which
`
`is external
`
`to the apparatus
`
`is particularly
`
`10
`
`
`
`preferably provided for bi-directional data transmission. It is thus possible
`
`to transmit not only digital data
`
`from
`
`the apparatuses to external
`
`processing devices but also from the external processing devices to the
`
`apparatuses according to the invention.
`
`5
`
`Preferably the interface is an infra-red interface which affords a high
`
`data transmission rate with at the same time good transmission quality.
`
`In a further preferred embodiment of the apparatuses the digital
`
`audio data are stored in the data-reduced format in the storage medium.
`
`That permits better utilisation of the storage capacity present in the storage
`
`10 medium. Particularly preferably, the digital audio data are also transmitted
`
`in the data-reduced format by way of the cable-less transmission interface.
`
`That markedly speeds up the transmission of the audio data to a processing
`
`device which is external to the apparatus.
`
`In addition preferably provided on the apparatuses is an analog high
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`15
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`level output connection and/or digital output connection for audio signals.
`
`That permits data transmission in analog or digital form to known recording
`
`and reproducing apparatuses.
`
`Preferably the apparatuses according to the invention also have a
`
`converting device for decoding data-reduced audio data so that, besides
`
`20
`
`data reduction prior to storage of the audio data, decoding of the data(cid:173)
`
`reduced audio data is also possible before same are transmitted to the
`
`digital output connection or to the digital/analog processing unit.
`
`For the input of control commands for controlling the apparatuses,
`
`the apparatuses according to the invention preferably have an input device.
`
`25
`
`The apparatuses also preferably have a display device for displaying
`
`corresponding items of status or control information.
`
`So that the recording, processing and transmission apparatuses
`
`according to the invention and the reproduction apparatus according to the
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`invention can be used in a versatile manner, they are advantageously of a
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`30
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`portable configuration, in a light compact casing.
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`Advantageous developments of the invention are characterised by
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`the features of the appendant claims.
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`11
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`
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`This further invention is described by way of example hereinafter
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`with reference to the drawing in which:
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`Figure 3 is a block circuit diagram of the apparatus according to the
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`invention,
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`s
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`Figure 4 is a diagrammatic view of an input device of the apparatus
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`shown in Figure 3, and
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`Figure 5 is a time-presentation diagram of an audio recording.
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`The apparatus 1 illustrated in Figure 3
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`includes three apparatus
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`regions, more specifically an analog signal processing region 3, a digital
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`10
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`signal processing region 5 and a digital interface region 7.
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`The analog signal processing region 3
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`includes a
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`line-in
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`input
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`connection 9, a microphone input connection 11 which is connected to a
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`microphone pre-amplifier 13, a first change-over switch 15 with which a
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`downstream-disposed
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`input amplifier 17
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`is connected either
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`to
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`the
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`15 microphone pre-amplifier or the line-in input connection, a second change(cid:173)
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`over switch 19 with which a source can be selected for a downstream(cid:173)
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`disposed headset amplifier 21 or a line-out output connection 23 and a
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`headset output connection 22.
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`A microphone signal at the microphone input connection 11 is raised
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`20
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`by the microphone pre-amplifier 13 to the level which is typical for the line(cid:173)
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`in input connection 9. The first change-over switch 15 selects whether the
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`microphone signal or the signal at the line-in input connection 9 is passed
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`along as the input signal. The first change-over switch 15 is controlled by a
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`microcontroller 25 which is to be functionally associated with the digital
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`25
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`interface region 7. The input amplifier 17 serves for level setting of the
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`input signal, the level of the input signal being effected by means of a level
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`control 18 in the input amplifier 17, by way of the microcontroller 25. In
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`that case a downstream-disposed peak LED 27 can warn of overdriving of a
`downstream-disposed analog/digital converter 29 which belongs to the.
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`30
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`digital signal processing region 5.
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`The second change-over switch 19 which is also controlled by way of
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`the microcontroller 25 selects which analog signal is passed to the headset
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`amplifier 21 and at the same time the line-out output connection 23. This
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`12
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`
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`can be either the signal coming from the input amplifier 17 or the analog
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`signal of a digital/analog converter 31 which is also a component of the
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`digital signal processing region 5.
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`The headset amplifier 21 serves to supply a connected external
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`5
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`headset (not shown), wherein volume is controlled by means of a level
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`controi 20 integrated in the headset amplifier, also by the microcontroller
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`25.
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`The digital signal processing region 5
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`includes the analog/digital
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`converter 29, the digital/analog converter 31, a digital input connection 33,
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`10
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`a digital output connection 34, the digital signal processor 25 (DSP) and a
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`third change-over switch 37.
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`The analog/digital converter converts . the signal from the input
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`amplifier 17 into a linear data signal which is transmitted to the digital
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`signal processor 35. The digital/analog converter 31 converts a linear data
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`15
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`signal which comes from the digital signal processor 35 and which is also
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`applied to the digital output connection 34 into an analog output signal
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`which is passed to a connection of the second change-over switch 19. By
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`way of example, the 24-bit converters from Crystal can be used as the
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`analog/digital converter 29 and the digital/analog converter 31. The digital
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`20
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`input connection 33 and the digital output connection 34 correspond in
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`terms of their properties to the Sony/Philips standard which originates from
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`consumer technology.
`The digital signal processor 35 is responsible for conversion from and
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`into a data-reduced format. In this respect in particular the MPEG audio
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`25
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`format is favoured as this represents an audio format which is already
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`wide-spread. For example, the Motorola-56302-DSP device is suitable as
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`the digital signal processor 35. The third change-over switch 37 connects
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`the signal input of the digital signal processor 35 either to the output of the
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`analog/digital converter 29 or to the digital input connection 33. In that
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`30
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`case control of the third change-over switch 37 is again effected by the
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`microcontroller 25.
`The digital interface region 7 includes a display device 39, an input
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`device 41, a storage medium 43, as a cable-less interface an infra-red
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`13
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`
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`interface 45 and the microcontroller 25. It will be appreciated that it is also
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`possible to implement an interface with cable.
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`In this case the display device 39 can be formed by an LC compact
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`display with a dot matrix, for example the PG12232-D from Actron. In this
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`s
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`case actuation of the display device 39
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`is effected directly by the
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`microcontroller 25. The input device can comprise pushbuttons or keys
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`which are connected by way of a matrix to the microcontroller 25. The
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`storage medium 43 which is either a flash-RAM or a dynamic RAM (SD(cid:173)
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`RAM) should have at least a storage capacity of 30 Megabytes. In this case
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`10
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`the storage medium 43 is fixedly integrated into the apparatus, in which
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`respect subsequent enlargement is neither intended nor possible. An
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`increase in the storage capacity of the storage medium 43 can however be
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`effected by suitable personnel by the subsequent insertion of other memory
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`components.
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`15
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`The infra-red interface 45 serves for loading and unloading the audio
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`data afld co-operates directly with an external processing apparatus, for
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`example a personal computer (PC) (not shown). In this respect the infra(cid:173)
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`red interface preferably complies with the IrDA 1.1 standard and has a data
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`transfer rate of 115 kbit/s