1. A method for power consumption optimization in a wearable camera, the method comprising:

monitoring a bit rate of a video stream captured by the wearable camera;

activating a motion sensor of the wearable camera when the bitrate is above a first bitrate threshold, and activating image stabilization of the video stream based on motion data from the motion sensor;

upon activation of the motion sensor and the image stabilization, analyzing whether the activation of the motion sensor and the image stabilization is beneficial for reducing the bit rate; and is

Keeping the motion sensor active and performing image stabilization based on motion data from the motion sensor if activation of the motion sensor and the image stabilization is beneficial for reducing the bit rate, otherwise deactivating the motion sensor.

2. The method of claim 1, wherein analyzing whether activation of the motion sensor and the image stabilization is beneficial for reducing the bit rate comprises:

analyzing the bitrate of the video stream after image stabilization of the video stream is activated, wherein activation of the motion sensor is beneficial to reduce the bitrate if the bitrate of the video stream after image stabilization of the video stream is below a second bitrate threshold, wherein the second threshold is less than or equal to 90% of the first bitrate threshold.

3. The method of claim 1, wherein the first bit rate threshold and/or the second bit rate threshold depends on a current state of charge of a battery of the wearable camera.

4. The method of claim 1, wherein the first bit rate threshold and/or the second bit rate threshold depend on available memory space in a local data store of the wearable camera.

5. The method of claim 1, wherein analyzing whether activation of the motion sensor and the image stabilization is beneficial for reducing the bit rate comprises:

analyzing motion data from the motion sensor, wherein activation of the motion sensor and the image stabilization is beneficial to reduce the bit rate if the motion data indicates that the wearable camera is shaking.

6. The method of claim 1, wherein analyzing whether activation of the motion sensor and the image stabilization is beneficial for reducing the bit rate comprises:

analyzing motion data from the motion sensor, wherein activation of the motion sensor and the image stabilization is beneficial to reduce the bit rate if the motion data indicates that the wearable camera is located at the same location.

7. The method of claim 1, further comprising:

keeping image stabilization of the motion sensor and the video stream active for a predetermined period of time before performing the step of analyzing again whether activation of the motion sensor and the image stabilization is beneficial for reducing the bit rate.

8. The method of claim 1, further comprising:

keeping the motion sensor and the image of the video stream steady active until the motion data indicates a steady wearable camera.

9. The method of claim 1, further comprising:

storing the video stream in a local data store of the wearable camera and/or wirelessly transmitting the video stream from the wearable camera.

10. A non-transitory computer-readable storage medium having instructions stored thereon, the instructions when executed on a device having processing capabilities to implement the method of claim 1.

11. A wearable camera, comprising:

an image sensor configured to capture image data;

an encoder configured to encode the image data into a video stream;

a motion sensor configured to measure motion data of the wearable camera, wherein the motion sensor is configured to be set in an active mode or an inactive mode;

a battery configured to supply power to the wearable camera; and

circuitry configured to perform:

a bit rate monitoring function configured to monitor a bit rate of the video stream,

an image stabilization function configured to image-stabilize the image data based on motion data from the motion sensor,

a sensor mode setting function configured to set the motion sensor in the active mode when the bit rate is above a first bit rate threshold, an

An analysis function configured to analyze whether activation of the motion sensor and the image stabilization is beneficial to reduce the bit rate when the activation of the motion sensor and the image stabilization is activated,

wherein the analysis function is further configured to: instructing the sensor mode setting function to keep the motion sensor in the active mode and instructing the image stabilization function to perform image stabilization if activation of the motion sensor and the image stabilization is beneficial to reducing the bit rate, otherwise instructing the sensor mode setting function to set the motion sensor in the inactive mode.

12. The wearable camera of claim 11, wherein the analysis function is configured to analyze whether activation of the motion sensor and image stabilization is beneficial to reduce the bitrate by analyzing the bitrate of the video stream after image stabilization by the image stabilization function, wherein activation of the motion sensor and image stabilization is beneficial to reduce the bitrate if the bitrate of the video stream after image stabilization is below a second bitrate threshold, wherein the second threshold is less than or equal to 90% of the first bitrate threshold.

13. The wearable camera of claim 11, wherein the analysis function is configured to analyze whether activation of the motion sensor and the image stabilization is beneficial to reduce the bit rate by analyzing the motion data, wherein activation of the motion sensor and the image stabilization is beneficial to reduce the bit rate if the motion data indicates that the wearable camera is shaking and/or the wearable camera is in the same location.

14. Wearable camera according to claim 11, wherein the first and/or second bit rate threshold depends on the current state of charge of the battery of the wearable camera and/or the available storage space in the local data storage of the wearable camera.

15. The wearable camera of claim 11, further comprising:

a local data store configured to store the video stream and/or a transmitter configured to wirelessly transmit the video stream.

Background

Wearable cameras (e.g., by the police) are used to capture video and other data during patrols and accidents. Such a camera may also be referred to as a Body Worn Camera (BWC). Wearable cameras are typically battery powered. Thus, there are limitations on the power available to the wearable camera. Thus, there is a need to optimize power consumption in wearable cameras.

Disclosure of Invention

It is an object of the present invention to facilitate battery power savings in wearable cameras. It is another object of the invention to facilitate bit rate savings for video streams generated by wearable cameras.

According to a first aspect, a method for power consumption optimization in a wearable camera is provided. The method comprises the following steps: monitoring a bit rate of a video stream captured by a wearable camera; activating a motion sensor of the wearable camera when the bitrate is above a first bitrate threshold; upon activation of the motion sensor, analyzing whether the activation of the motion sensor is beneficial for reducing the bit rate; and keeping the motion sensor active and performing image stabilization based on motion data from the motion sensor in case activation of the motion sensor is beneficial for reducing the bit rate, otherwise deactivating the motion sensor.

By only putting the motion sensor of the wearable camera in an active mode when the motion data measured by the motion sensor requires other functions of the wearable camera, such as image stabilization, power consumption in the wearable camera may be saved. Thus, the operation time of the wearable camera can be prolonged. Furthermore, power consumption optimization with respect to the bit rate of the video stream may be provided. This is because battery power can be used in a bit rate optimized manner. When bit rate savings are available with the motion sensor being made active, the motion sensor may be kept active to provide motion data to perform bit rate savings image stabilization.

The method may further include activating image stabilization of the video stream based on motion data from the motion sensor. Analyzing whether activation of the motion sensor is beneficial for reducing the bit rate may include analyzing the bit rate of the video stream after image stabilization of the video stream is activated. In case the bit rate of the video stream after image stabilization of the video stream is below the second bit rate threshold, the activation of the motion sensor may be beneficial to reduce the bit rate. The second threshold may be less than or equal to 90% of the first bitrate threshold. Depending on the scene and mode of motion, the acceptable bit rate savings may be about 10% to 50% due to image stabilization based on motion data. Thus, in case the image stabilization reduces the bit rate of the video stream by more than 10%, the activation of the motion sensor is beneficial and the motion sensor and the image stabilization should be kept active. Otherwise, activation of the motion sensor is not beneficial and power consumption may be saved by deactivating the motion sensor and/or image stabilization. By keeping the motion sensor and image stabilization active, optimization of bit rate usage versus battery power usage may be provided. Thus, battery power may be used to reduce the bit rate of the video stream.

The first bit rate threshold may depend on a current state of charge of a battery of the wearable camera. The second bit rate threshold may depend on a current state of charge of a battery of the wearable camera. Thus, the first and/or second bit rate threshold may be dynamically set such that in case the charge state of the battery is becoming too low, the remaining charge state will not be spent on activation of the motion sensor and possibly also image stabilization.

The first bit rate threshold may depend on available memory space in the local data storage of the wearable camera. The second bitrate threshold may depend on the available memory space in the local data storage of the wearable camera. Thus, the first bitrate threshold and/or the second bitrate threshold can be dynamically set such that the available storage space can be saved by more easily activating image stabilization based on motion data in case the recording of the video stream has taken up an unexpectedly large space (e.g. due to large noise).

Analyzing whether activation of the motion sensor is beneficial for reducing the bit rate may include analyzing motion data from the motion sensor. In the event that the motion data indicates that the wearable camera is shaking, activation of the motion sensor may be beneficial to reduce the bit rate. The shaking of the wearable camera may be due to the person wearing it being heavy and breathing, for example after running. Herein, the wearable camera is shaking means that the wearable camera is oscillating. In order to shake the wearable camera, the oscillation is preferably periodic. Furthermore, to shake the wearable camera, the oscillation preferably has an amplitude above a shake threshold. Typically, in case the wearable camera is shaking, activating image stabilization based on motion data is reducing the bit rate, and thus the motion sensor and the image stabilization should be kept active in order to reduce the bit rate. Otherwise, activation of the motion sensor is not beneficial and power consumption may be saved by deactivating the motion sensor and/or image stabilization. By keeping the motion sensor and image stabilization active, optimization of bit rate usage versus battery power usage may be provided. Thus, battery power may be used to reduce the bit rate of the video stream.

Alternatively or in combination, the activation of the motion sensor may be beneficial to reduce the bit rate in case the motion data indicates that the wearable camera is located at the same location. Herein, the wearable cameras being located in the same position means that the wearable cameras do not move in the dominant direction. The movement in the dominant direction may for example be that the person wearing the wearable camera is walking or running. According to the inventors' experience, image stabilization is not very effective when moving in the dominant direction, and the motion sensor and also the image stabilization may be deactivated in order to save battery power.

The method may comprise keeping the motion sensor and the image of the video stream steady active for a predetermined period of time before the step of analysing whether the activation of the motion sensor is beneficial for reducing the bit rate is performed again. Thus, by not requiring the analysis steps to be performed so frequently, processing power may be conserved.

The method may include keeping the motion sensor and the image stabilization of the video stream active until the motion data indicates a stable wearable camera. In this context, a stable wearable camera means that the motion data indicates that the motion (typically an oscillating motion) of the wearable camera is below a threshold. Thus, the wearable camera is no longer shaken. In case of a stabilized camera, the motion sensor and image stabilization can be deactivated, since the image stabilization will not bring about any bit rate reduction. The disabling of the motion sensor and image stabilization will result in battery power savings.

The method may include storing the video stream in a local data store of the wearable camera. The method may include wirelessly transmitting a video stream from a wearable camera.

According to a second aspect, a non-transitory computer-readable recording medium is provided. The non-transitory computer-readable recording medium has stored thereon instructions, possibly in the form of computer-readable program code, which when executed on a device having processing capabilities, is configured to perform the method of the first aspect. The device with processing capability may be a wearable camera, such as a body worn camera or a tachograph.

The above-mentioned features of the method according to the first aspect also apply to this second aspect, when applicable. To avoid excessive repetition, reference is made to the above.

According to a third aspect, a wearable camera is provided. This wearable camera includes: an image sensor configured to capture image data; an encoder configured to encode the image data into a video stream; a motion sensor configured to measure motion data of the wearable camera, wherein the motion sensor is configured to be set in an active mode or an inactive mode; a battery configured to supply power to the wearable camera; and a circuit. The circuitry is configured to perform: a bit rate monitoring function configured to monitor a bit rate of the video stream; an image stabilization function configured to image-stabilize image data based on motion data from the motion sensor; a sensor mode setting function configured to set the motion sensor in an active mode when the bit rate is above a first bit rate threshold; and an analysis function configured to analyze whether activation of the motion sensor is beneficial to reduce the bit rate when the motion sensor is activated. Wherein the analysis function is further configured to: in case activation of the motion sensor is beneficial for reducing the bit rate, the sensor mode setting function is instructed to keep the motion sensor in an active mode and the image stabilization function is instructed to perform image stabilization, otherwise the sensor mode setting function is instructed to set the motion sensor in an inactive mode.

The analysis function may be configured to analyze whether activation of the motion sensor is beneficial to reduce the bit rate by analyzing the bit rate of the video stream after image stabilization by the image stabilization function. In case the bit rate of the video stream after image stabilization is below the second bit rate threshold, the activation of the motion sensor may be beneficial to reduce the bit rate. The second threshold may be less than or equal to 90% of the first bitrate threshold.

The analysis function may be configured to analyze whether activation of the motion sensor is beneficial for reducing the bit rate by analyzing the motion data. In the event that the motion data indicates that the wearable camera is shaking and/or the wearable camera is located in the same location, activation of the motion sensor may be beneficial to reduce the bit rate.

The wearable camera may further include a local data store configured to store the video stream. The wearable camera may further include a transmitter configured to wirelessly transmit the video stream.

Furthermore, the above-mentioned features of the method according to the first aspect also apply to this third aspect, when applicable. To avoid excessive repetition, reference is made to the above.

Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. It should be understood, however, that the detailed description and the specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the scope of the invention will become apparent to those skilled in the art from this detailed description.

It is to be understood, therefore, that this invention is not limited to the particular component parts of the devices described or acts of the methods described, as such devices and methods may vary. It is also to be understood that the terminology used herein is for the purpose of describing particular embodiments only, and is not intended to be limiting. It must be noted that, as used in the specification and the appended claims, the articles "a," "an," "the," and "said" are intended to mean that there are one or more of the elements, unless the context clearly dictates otherwise. Thus, for example, reference to "a unit" or "the unit" may include several devices, and the like. Furthermore, the terms "comprising," "including," "containing," and similar language do not exclude other elements or steps.

Drawings

The above and other aspects of the invention will now be described in more detail with reference to the accompanying drawings. The drawings should not be considered limiting; rather, they are used for explanation and understanding.

As illustrated in the drawings, the sizes of layers and regions may be exaggerated for illustrative purposes, and thus, are provided to illustrate a general structure. Like reference numerals refer to like elements throughout.

Fig. 1 is a schematic block diagram of a wearable camera.

Fig. 2 is a block diagram of a method for power consumption optimization in a wearable camera.

Detailed Description

The present invention now will be described more fully hereinafter with reference to the accompanying drawings, in which presently preferred embodiments of the invention are shown. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided for thoroughness and completeness, and to fully convey the scope of the invention to the skilled person.

Fig. 1 illustrates a wearable camera 100. The wearable camera 100 may be a Body Worn Camera (BWC). The wearable camera 100 may be a tachograph. The wearable camera 100 may be used (e.g., by police) to capture video and possibly other data during patrols and accidents. The captured data may then be needed as evidence, for example, in investigating criminals and prosecuting suspicious criminals. To preserve the captured data, a data management system external to the wearable camera 100, such as a video management system or an evidence management system, may be used. Such data management systems typically provide for storage of the captured data and also viewing the captured data either in real time or as a playback of the recorded data. Typically, the wearable camera 100 is battery powered and has a limited bit rate. The latter is due to limited local data storage and/or bandwidth limitations of the wireless connection to the data management system. The wearable camera 100 includes an image sensor 110, an encoder 120, a motion sensor 130, a battery 140, circuitry 150, and a memory 160.

The battery 140 is configured to supply power to the wearable camera 100 (i.e., the components of the wearable camera that require power). The battery 140 may be a rechargeable battery.

The image sensor 110 is configured to capture image data. The image data may be, for example, data of an image frame. Image sensors and the capture of image data are well known to those skilled in the art and will not be discussed in more detail in this disclosure.

The encoder 120 is configured to encode image data captured by the image sensor 110 into a video stream, and the video stream provided by the encoder 120 is sometimes referred to as an encoded video stream. In general, the video encoder 120 is configured to encode some of the image frames of the video stream as key frames and some of the image frames of the video stream as delta frames. A key frame is an encoded video frame that does not require information from other encoded video frames to be decoded. Therefore, the key frame is encoded based on information from the image frame of the video data, and the key frame is set to correspond to the information from the image frame of the video data. In general, similarities within image frames are used to encode image frames into key frames. In video coding, key frames are also referred to as intra frames, often referred to as I frames. Image frames of a video stream between two key frames are encoded as delta frames. Typically, a delta frame includes only changes that occur from one frame to the next. Thus, delta frames typically include less data than key frames. In video coding, delta frames are also referred to as inter-frames, often referred to as P-frames or B-frames. P-frames refer to previous frames for data reference. Therefore, in order to decode a P frame, the content of the previous frame must be known. B-frames may refer to both previous and forward frames used for data reference. Therefore, in order to decode a B-frame, the contents of both the previous frame and the forward frame must be known.

The wearable camera 100 may further include a local data store 170. The local data store 170 may be configured to store video streams. Local data storage typically has limited data storage capacity. The local data store 170 may be any type of local data store suitable for storing video streams. For example, the local data store 170 may be in the form of an SD card reader and an SD card. Another example of the local data storage 170 may be in the form of flash memory, such as NAND flash memory.

To transfer video data (e.g., a video stream) stored locally on the wearable camera 100 to the data management system, the wearable camera 100 may be configured to be docked to a docking station. When docked in the docking station, locally stored video data may be transferred from the wearable camera 100 to the data management system. Further, the battery 140 of the wearable camera 100 may be charged when docked in the docking station.

The wearable camera 100 may further comprise a transmitter 180. The transmitter 180 may be configured to wirelessly transmit the video stream to a data management system. The transmitter 180 may be configured to continuously transmit the captured video stream to the video management system. Wireless transmissions are typically limited due to the bandwidth available for wireless transmissions.

The motion sensor 130 is configured to measure motion data of the wearable device. The motion sensor 130 may include a gyroscope and/or an accelerometer. The gyroscope is configured to measure motion data in the form of the orientation and/or angular velocity of the wearable camera 100. The accelerometer is configured to measure motion data in the form of acceleration (or rate of change of velocity) of wearable camera 100 in its own instantaneous stationary frame. The motion sensor 130 is configured to sample motion data as a function of time. Motion sensor 130 may be set to be either in an active mode or in an inactive mode. Thus, at a particular time, motion sensor 130 is active or inactive. In active mode, motion sensor 130 is measuring motion data. In the active mode, motion sensor 130 is consuming power from battery 140. In the inactive mode, motion sensor 130 is not measuring motion data. In the inactive mode, motion sensor 130 is not consuming power from battery 140 or is consuming very limited power from battery 140. Thus, in active mode, motion sensor 130 is consuming much more power from battery 140 than in inactive mode.

The circuit 150 is configured to perform all of the functions of the wearable camera 100. The circuit 150 may include a processor 152, such as a Central Processing Unit (CPU), microcontroller, or microprocessor. The processor 152 is configured to execute program code stored in the memory 160 in order to perform the functions of the wearable camera 100.

The memory 160 may be one or more of a buffer, a flash memory, a hard drive, a removable media, a volatile memory, a non-volatile memory, a Random Access Memory (RAM), or another suitable device. In a typical arrangement, the memory 160 may include non-volatile memory for long-term data storage and volatile memory for use as system memory for the circuit 150. The memory 160 may exchange data with the circuit 150 via a data bus. Accompanying control lines and address buses may also be present between memory 160 and circuitry 150.

The functionality of the wearable camera 100 may be presented in the form of executable logic routines (e.g., lines of code, software programs, etc.) stored on a non-transitory computer readable medium (e.g., memory 160) of the wearable camera 100 and executed by the circuitry 150 (e.g., using the processor 152). Further, the functionality of the wearable camera 100 may be a stand-alone software application or form part of a software application that performs additional tasks related to the wearable camera 100. The described functionality may be considered a method that a processing unit (e.g., the processor 152 of the circuit 150) is configured to perform. Further, while the functions described may be implemented in software, such functions could also be carried out in dedicated hardware or firmware, or some combination of hardware, firmware, and/or software.

The circuit 150 may be configured to perform a bit rate monitoring function 421. The bit rate monitoring function 421 is configured to monitor the bit rate of the video stream encoded by the encoder 120.

The circuit 150 may be configured to perform an image stabilization function 422. The image stabilization function 422 is configured to image stabilize video data captured by the wearable camera 100 based on motion data from the motion sensor 130 in the active mode. Thus, the image stabilization function 422 relies on motion data from the motion sensor 130 as input data for performing image stabilization. The image stabilization function 422 may be set to be in an active mode or in an inactive mode. Thus, at a particular time, the image stabilization function 422 is active or inactive. In the active mode, the image stabilization function 422 is performing image stabilization of video data captured by the wearable camera 100. In the active mode, the image stabilization function 422 is consuming power from the battery 140. In the inactive mode, the image stabilization function 422 is not performing image stabilization of video data captured by the wearable camera 100. In the inactive mode, the image stabilization function 422 is not consuming power from the battery 140 or is consuming very limited power from the battery 140. Thus, in active mode, the image stabilization function 422 is consuming much more power from the battery than in inactive mode.

The circuit 150 may be configured to perform a sensor mode setting function 423. Sensor mode setting function 423 is configured to set motion sensor 130 in either an active mode or in an inactive mode. In particular, sensor mode setting function 423 may be configured to set motion sensor 130 in the active mode when the bit rate is above a first bit rate threshold. The first bit rate threshold may be a preset threshold. The first bit rate threshold may depend on the current state of charge of the battery 140 of the wearable camera 100. Thus, the first bit rate threshold may be dynamically set such that in case the state of charge of the battery 140 is becoming too low, the remaining state of charge will not be spent on activation of the motion sensor 130 and possibly also image stabilization. Alternatively, the first bit rate threshold may depend on the available storage space in the local data store 170. Thus, the first bit rate threshold can be dynamically set such that in case the recording of the video stream (e.g. due to large noise) already takes up an unexpectedly large space, the available storage space can be saved by more easily activating the image stabilization based on the motion data.

The circuit 150 may be configured to perform an analysis function 424. The analysis function 424 is configured to analyze whether activation of the motion sensor 130 is beneficial for reducing the bit rate. Accordingly, the analysis function 424 is configured to be performed upon activation of the motion sensor 130. The analysis function 424 may be configured to analyze whether activation of the motion sensor 130 is beneficial to reducing the bit rate in various ways.

The analysis function 424 may be configured to analyze whether activation of the motion sensor 130 is beneficial to reduce the bit rate by analyzing the bit rate of the video stream after image stabilization by the image stabilization function 422 is performed. Thus, the bit rate of the analysis video stream is activated after image stabilization by the image stabilization function 422. In case the bit rate of the video stream after image stabilization of the video stream is below the second bit rate threshold, the activation of the motion sensor 130 may be beneficial to reduce the bit rate. The second threshold may be less than or equal to 90% of the first bitrate threshold. Depending on the scene and mode of motion, the acceptable bit rate savings may be about 10% to 50% due to image stabilization based on motion data. Thus, in case the image stabilization by the image stabilization function 422 reduces the bit rate of the video stream by more than 10%, the activation of the motion sensor 130 is beneficial and the motion sensor 130 and the image stabilization function 422 should be kept active. Otherwise, activation of motion sensor 130 is not beneficial, and power consumption may be saved by deactivating motion sensor 130 and/or image stabilization function 422.

Alternatively or in combination, the analysis function 424 may be configured to analyze whether activation of the motion sensor 130 is beneficial for reducing the bit rate by analyzing the motion data. In the event that the motion data indicates that the wearable camera 100 is shaking, activation of the motion sensor 130 may be beneficial to reduce the bit rate. The shaking of the wearable camera 100 may be due to the person wearing it being heavy and breathing, for example, after running. Herein, the wearable camera 100 being shaken means that the wearable camera 100 is oscillating. In order to shake the wearable camera 100, the oscillation is preferably periodic. Further, to shake the wearable camera 100, the oscillation preferably has an amplitude above a shake threshold. Typically, in case the wearable camera 100 is shaking, activating image stabilization based on motion data is reducing the bit rate, and thus the motion sensor 130 and the image stabilization function 422 should be kept active in order to reduce the bit rate. Otherwise, activation of motion sensor 130 is not beneficial, and power consumption may be saved by deactivating motion sensor 130 and/or image stabilization function 422.

Alternatively or in combination, the analysis function 424 may be configured to analyze whether activation of the motion sensor 130 is beneficial for reducing the bit rate by analyzing the motion data. In the event that the motion data indicates that the wearable camera 100 is located at the same location, activation of the motion sensor 130 may be beneficial to reduce the bit rate. Herein, the wearable camera 100 being in the same position means that the wearable camera 100 is not moving in the dominant direction. The motion in the dominant direction may be, for example, that the person wearing the wearable camera 100 is walking or running. According to the inventors' experience, image stabilization is not very effective when moving in the dominant direction, and the motion sensor 130 and also the image stabilization function 422 may be deactivated in order to save battery power.

In the event that activation of the motion sensor 130 is beneficial for reducing the bit rate, the analysis function 424 may be further configured to instruct the sensor mode setting function 423 to keep the motion sensor 130 and generally also the image stabilization function 422 active. Otherwise, the analysis function 424 may be configured to instruct the sensor mode setting function 423 to set the motion sensor 130 and generally also the image stabilization function 422 to be in the inactive mode. The analysis function 424 may actively instruct the sensor mode setting function 423 to keep the motion sensor 130 and generally also the image stabilization function 422 active. Alternatively, the analysis function 424 may not actively instruct the sensor mode setting function 423 to keep the motion sensor 130 and typically also the image stabilization function 422 active, i.e. the instructions for keeping the motion sensor 130 and typically also the image stabilization function 422 active may be in the form of no instructions being sent to the sensor mode setting function 423. Thus, the motion sensor 130 and generally also the image stabilization function 422 will be in active mode until the sensor mode setting function 423 is otherwise informed.

The analysis function 424 may be configured to keep the motion sensor 130 and generally also the image stabilization function 422 active for a predetermined period of time before performing a new analysis of whether the activation of the motion sensor 130 is beneficial for reducing the bit rate. The time period may be in minutes. Alternatively or in combination, the analysis function 424 may be configured to keep the motion sensor 130 and typically also the image stabilization function 422 active until the motion data indicates a stable wearable camera 100. Herein, a stable wearable camera 100 means that the motion data indicates that the motion (typically oscillatory motion) of the wearable camera 100 is below a threshold.

A method 200 for power consumption optimization in the wearable camera 100 will be discussed in conjunction with fig. 2. The method 200 is based on the inventors' understanding that: by only having the motion sensor 130 of the wearable camera 100 in an active mode when motion data measured by the motion sensor 130 requires other functions of the wearable camera 100, such as image stabilization, power consumption in the wearable camera 100 may be saved. Thus, the present approach may save power consumption and, therefore, may also save battery life at the wearable camera 100. This may be performed at the same time that the bit rate optimization may be performed. This is because this approach allows motion data from the motion sensor 130 to be used when the bit rate in the video stream captured by the wearable camera 100 can be reduced. Thus, the use of storage space in the local data store 170 and/or the use of bandwidth for transmitting the captured video stream may be optimized.

Some of all of the steps of method 200 may be performed by the functions of wearable camera 100 described above. The method includes a flowing step. The steps may be performed in any suitable order.

The bit rate of the video stream captured by the wearable camera 100 is monitored S202. Activating S204 the motion sensor 130 of the wearable camera 100 when the bitrate is above the first bitrate threshold. Upon activation of the motion sensor 130, it is analyzed S206 whether the activation of the motion sensor 130 is beneficial for reducing the bit rate. In case the activation of the motion sensor 130 is beneficial for reducing the bit rate, the motion sensor 130 is kept S208 active and image stabilization is performed S210 based on motion data from the motion sensor 130, otherwise the motion sensor 130 is deactivated S212.

The method may comprise activating S205 image stabilization of the video stream based on the motion data from the motion sensor 130. In the case where this step is performed, the step of performing S210 image stabilization based on the motion data from the motion sensor 130 may be said to keep image stabilization based on the motion data from the motion sensor 130 active.

The step of analyzing S206 whether the activation of the motion sensor 130 is beneficial for reducing the bit rate may comprise analyzing the bit rate of the video stream after the image stabilization of the video stream is activated. In this case, in case the bit rate of the video stream after image stabilization of the video stream is lower than the second bit rate threshold, the activation of the motion sensor 130 is beneficial to reduce the bit rate. As mentioned above, the second threshold is preferably less than or equal to 90% of the first bitrate threshold. Further, as also mentioned above, the first bit rate threshold and/or the second bit rate threshold may depend on the current state of charge of the battery 140 of the wearable camera 100. Furthermore, as also mentioned above, the first bit rate threshold and/or the second bit rate threshold may depend on the available memory space in the local data storage 170 of the wearable camera 100.

The step of analyzing S206 whether the activation of the motion sensor 130 is beneficial for reducing the bit rate may comprise analyzing motion data from the motion sensor 130. In such a case, where the motion data indicates that the wearable camera 100 is shaking, the activation of the motion sensor 130 may be beneficial to reduce the bit rate, shaking of the wearable camera 100 discussed above in connection with the analysis function 424. Further, in such a case, where the motion data indicates that the wearable camera 100 is located at the same location, the activation of the motion sensor 130 may be beneficial to reduce the bit rate, the location of the wearable camera 100 being the same location discussed above in connection with the analysis function 424.

The method may further comprise keeping the motion sensor 130 and the image of the video stream steady active for a predetermined period of time before performing the step of analyzing S206 again whether the activation of the motion sensor 130 is beneficial for reducing the bit rate.

The method may further include keeping the motion sensor 130 and the image stabilization of the video stream active until the motion data indicates a stable wearable camera 100. The stability of the wearable camera is discussed above.

The method may further include storing the video stream in a local data store 170 of the wearable camera 100. The method may further include wirelessly transmitting the video stream from the wearable camera 100.

The person skilled in the art realizes that the present invention by no means is limited to the preferred embodiments described above. On the contrary, many modifications and variations are possible within the scope of the appended claims.

For example, the wearable camera 100 may be used by the police. On patrol, the police may use wearable camera 100 for continuous recording. However, continuous recording requires a high capacity of the local data store 170, and the data captured most of the time will not be very interesting. Therefore, it is generally preferred to record only on demand. To this end, the wearable camera 100 may include an activation button that the police officer can easily activate and deactivate when needed.

In addition, the wearable camera 100 may include a video buffer. The video buffer is configured to buffer video data. Upon activation of the recording by the wearable camera 100, the video data in the video buffer may be added to the video stream. By doing so, events that occur prior to activation can be recorded as part of the video stream. The video buffer may be configured to buffer video data for a period of up to one minute or several minutes before activating recording by the wearable camera 100. The video data buffered in the video buffer may be stored without image stabilization of the video stream based on the motion data having been performed. Thus, the motion sensor 130 does not need to be active until the recording by the wearable camera 100 is activated. Image stabilization of the buffered video data may be performed as a post-process using features depicted in the video stream when using video data from the video buffer.

In addition, variations to the disclosed embodiments can be understood and effected by those skilled in the art in practicing the claimed invention, from a study of the drawings, the disclosure, and the appended claims.