Telephonic communications – Audio message storage – retrieval – or synthesis – Message management
Reexamination Certificate
1998-06-22
2001-05-15
Nguyen, Lee (Department: 2746)
Telephonic communications
Audio message storage, retrieval, or synthesis
Message management
C455S412100, C455S413000, C455S556200, C379S088160, C379S088220, C379S088280, C704S201000, C704S270000
Reexamination Certificate
active
06233320
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to improved methods and apparatus for recording and playing back speech, and more particularly, to the recording and playing back of two way telephonic conversations using a digital wireless phone.
2. Dissussion of the Prior Art
Many telephone answering devices (TADs, also known as “answering machines”) provide a “two way conversation record” feature, which allows the user to record both near-end and far-end sides of a telephone conversation and later playback the recorded two way conversation. When the user of the TAD, also referred to as the near-end party, activates the conversation record feature of the TAD, then a telephone conversation between the user and a far-end party is recorded as follows. The far-end and the near-end audio speech signals are mixed (i.e. added together with appropriate gains), and the resulting mixed audio signal is recorded in the same way that a message is recorded on the TAD. In particular, if the TAD is digital, the mixed audio signal is fed into a mixed speech encoder for conversion to speech packets which are written or saved into a memory.
Play back of the recorded mixed conversation in the TAD is performed in exactly the same way as a playback of a recorded message. More particularly, if the TAD is digital, the stored speech packets are fed into a speech decoder which synthesizes and reconstructs the mixed audio signal for input to audio output circuits including a speaker.
Mobile wireless telephones are often used in situations where it is difficult for the user to write notes of important details of telephonic conversations. Therefore, the feature of two way conversation recording is even more useful for wireless phones than for stationary, wired phones or TADs.
Many wireless phones include a nonvolatile memory (“recording memory”) and a processing unit similar to the ones found in a digital TAD. Thus, adding a conversation recording capability to wireless phones is easily achieved with minimal cost, while providing a great benefit to the user.
The method of conversation recording used in TADs is suitable for implementation in analog wireless phones. However, using this recording method in digital wireless phones suffers from various drawbacks, such as exceeding the capability of typical digital signal processors (DSPs) included in wireless digital phones. Thus, a more complex and costly DSP is required. Further, the quality of the played-back recorded speech is degraded due to tandeming, as will be described below.
FIG. 1
shows a conventional wireless digital telephone
10
having a DSP
12
which performs numerous functions in a very short time to maintain an acceptable quality of telephonic conversations. During a conversation or call, the DSP functions include filtering, coding, decoding, error correction, tone generation, echo cancellation, muting and voice activity detection. These and other tasks increase the workload of the DSP, referred to as MIPS usage of the DSP, where MIPS is the acronym for million instructions per second.
The DSP
12
communicates with a nonvolatile memory
14
for storing information, a codec
16
for converting signals between digital and analog formats, a microcontroller
18
for managing operation of the phone such as detection of pressed keys, and a transceiver
20
. The transceiver
20
is connected to an antenna
22
for the transmission and reception of signals. The codec
16
is also connected to a microphone
24
and a speaker
26
.
The microcontroller
18
and transceiver
20
are connected to a system bus
28
. Other elements of the phone
10
are connected to the system bus
28
, such as a hardware control unit
30
, a hardware monitor
32
, a display
34
, a keypad
36
and memory units which include a read only memory (ROM)
38
and a random access memory (RAM)
40
.
FIG. 2
shows in greater detail modules used for recording and playback of telephonic conversations in a conventional digital wireless telephone
50
. These modules include a cellular phone operation module
52
, a conversation record module
54
, and a conversation playback module
56
.
The operation module
52
includes the codec
16
which is connected to the microphone
24
and to a speaker
26
. Speech or audio signals from the near-end, i.e., the phone user, are provided from the microphone
24
to the codec
16
, which digitizes the speech and provides digital transmission speech samples to a speech encoder
58
. The speech encoder
58
encodes the digital transmission speech samples into a compressed form and provides digital transmission speech packets to a transmission channel encoder
60
, which performs error correction encoding, and outputs a transmission bit stream to the transceiver
20
for modulation and transmission to the far-end.
Modulated radio frequency (RF) signals are received by the transceiver
20
from the far-end through the antenna
22
shown in FIG.
1
. The received bit stream undergoes the reverse operations of the transmission bit stream. In particular, the received bit stream is decoded by a reception channel decoder
62
to provide reception digital speech packets to a reception speech decoder
64
. The reception speech decoder
64
converts the reception digital speech packets to reception digital speech samples which are provided to the codec
16
for conversion to analog form and output to audio circuits and the speaker
26
for playback, as is typically performed in wireless communications.
Recording two way conversations between a far-end user and a near-end user, namely, the user of the conventional record and playback wireless telephone
50
, is performed as follows. The transmission speech samples from the codec
16
and the reception speech samples from the reception speech decoder
64
are provided to the conversation record module
54
of the conventional record and playback phone
50
.
In particular, transmission speech samples (i.e., near-end samples) and the reception speech samples (i.e., far-end samples) are provided to a mixer
70
through respective amplifiers
72
,
74
. The mixer
70
combines the near-end samples with the far-end samples and outputs mixed speech samples to a mixed speech encoder
76
. The mixed speech encoder
76
encodes the mixed speech samples to form mixed speech packets, which are provided to the nonvolatile memory
14
for storage.
FIG. 3
illustrates typical contents
90
of the nonvolatile memory
14
, namely, the recorded mixed conversation, where each stored frame
92
is a mixed speech packet formed from the encoding of the mixture or combination of the far-end and near-end speech samples.
Returning to
FIG. 2
, the recorded conversations are stored as a mixture or combination of the far-end and near-end speech packets, in the nonvolatile memory
14
. Playback of these conversations is provided by reading out the stored packets which are then provided to a mixed speech decoder
78
of the conversation playback module
56
. The mixed speech decoder
78
decodes the mixed speech packets and outputs mixed speech samples. The mixed speech samples are provided to the speaker
26
through a switch
80
and the codec
16
, which converts the mixed speech digital samples to analog audio signals.
The switch
80
selectively connects the mixed speech digital samples or the far-end reception speech samples from the speech decoder
64
to the codec
16
, under the control of the DSP, for example, in response to an input from the user of the phone
50
to playback the recorded conversation. Similar to playback initiation, recording may be initiated in response to a user input, such as pressing a key on the keypad
36
(FIG.
1
). Recording may be enabled in response to the user input using several approaches known in the art. For example, switches may be included at the inputs of the amplifiers
72
and
74
for controllably connecting and disconnecting these inputs to and from the operation module
52
, or in other words, to and from the transmission speech encoder
Law Offices of Peter H. Priest, PLLC
Lucent Technologies - Inc.
Nguyen Lee
Nguyen Simon
LandOfFree
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