Patent Publication Number: US-2023144529-A1

Title: Cadence-Based Playlists Management System

Description:
CROSS-REFERENCE TO RELATED APPLICATION(S) 
     This application is a continuation of U.S. Application No. 16/814,676, filed on Mar. 10, 2020, which is a continuation of U.S. Application No. 15/389,030, filed on Dec. 22, 2016, now U.S. Pat. No. 10,621,229, which is a continuation of U.S. Application No. 14/883,298, filed Oct. 14, 2015, now U.S. Pat. No. 9,563,700, which claims priority to U.S. Serial No. 62/163,845, filed on May 19, 2015, all of which are entitled CADENCE-BASED PLAYLISTS MANAGEMENT SYSTEM, the disclosures of which are hereby incorporated by reference in their entirety. To the extent appropriate a claim of priority is made to each of the above-disclosed applications. 
    
    
     BACKGROUND 
     Running, as well as many other recreation or fitness activities, includes repetitive motions. For example, running and walking involve repetitive steps, biking involves repetitive rotational movements, rowing involves repetitive strokes, and swimming involves repetitive strokes and kicks. There are of course many other recreation and fitness activities that also include various repetitive motions. These repetitive motion activities may be performed in place (e.g., using a treadmill, stationary bike, rowing machine, swimming machine, etc.) or in motion (e.g., on roads, trails, or tracks or in a pool or body of water, etc.). Cadence refers to the frequency of these repetitive motions and is often measured in terms of motions per minute (e.g., steps per minute, rotations per minute, strokes per minute, or kicks per minute). 
     Many people enjoy consuming media content, such as listening to audio content or watching video content, while running or engaging in other repetitive-motion activities. Examples of audio content include songs, albums, podcasts, audiobooks, etc. Examples of video content include movies, music videos, television episodes, etc. Using a mobile phone or other media-playback device a person can access large catalogs of media content. For example, a user can access an almost limitless catalog of media content through various free and subscription-based streaming services. Additionally, a user can store a large catalog of media content on his or her mobile device. 
     This nearly limitless access to media content introduces new challenges for users. For example, it may be difficult to find or select the right media content that complements a particular moment during a run or other repetitive-motion activity. 
     SUMMARY 
     In general terms, this disclosure is directed to a cadence-based playlists management system. In one possible configuration and by non-limiting example, the system operates to generate cadence-based playlists associated with different tempo ranges to support a user’s repetitive motion activity. Various aspects are described in this disclosure, which include, but are not limited to, the following aspects. 
     One aspect is a method of automatically playing back one or more media content items to support a repetitive motion activity. The method may include acquiring, using at least one computing device, a user’s cadence; retrieving, using the at least one computing device, a playlist associated with the cadence; and playing back the playlist on the at least one computing device. 
     Another aspect is a method of generating cadence-based playlists to support a repetitive motion activity. The method may include creating a plurality of cadence-based playlists, the plurality of cadence-based playlists associated with different tempo ranges, respectively; identifying tempi of the media content items; and associating the media content items with the plurality of cadence-based playlists, respectively, based on the tempi of the media content items, each cadence-based playlist including one or more of the media content items with the tempi of the one or more of the media content items within the tempo range of that playlist. 
     Yet another aspect is a computer-readable storage medium comprising software instructions that, when executed, cause one or more computing devices to acquire a user’s cadence; retrieve a playlist associated with the cadence, the playlist associated with a tempo range corresponding to the user’s cadence, and the playlist including one or more media content items with tempi of the media content items within the tempo range of the playlist; and play back the playlist on the one or more computing devices. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    illustrates an example system for managing cadence-based playlists. 
         FIG.  2    is a schematic illustration of an example system for managing cadence-based playlists. 
         FIG.  3    illustrates an example method of managing cadence-based playlists with the system of  FIG.  2   . 
         FIG.  4    illustrates an example method for performing an operation of  FIG.  3   . 
         FIG.  5    schematically illustrates an example playlist maintained in a media-delivery system of  FIG.  2   . 
         FIG.  6    schematically illustrates another example playlist maintained in a media-delivery system of  FIG.  2   . 
         FIG.  7    schematically illustrates yet another example playlist maintained in a media-delivery system of  FIG.  2   . 
         FIG.  8    illustrates an example structure of a cadence-based playlist. 
         FIG.  9    is an example data structure of repetitive-motion activity media metadata. 
         FIG.  10    is a flowchart illustrating an example method of performing an operation of  FIG.  3   . 
     
    
    
     DETAILED DESCRIPTION 
     Various embodiments will be described in detail with reference to the drawings, wherein like reference numerals represent like parts and assemblies throughout the several views. Reference to various embodiments does not limit the scope of the claims attached hereto. Additionally, any examples set forth in this specification are not intended to be limiting and merely set forth some of the many possible embodiments for the appended claims. 
     Users of media-playback devices often consume media content while engaging in various activities, including repetitive motion activities. As noted above, examples of repetitive-motion activities may include swimming, biking, running, rowing, and other activities. Consuming media content may include one or more of listening to audio content, watching video content, or consuming other types of media content. For ease of explanation, the embodiments described in this application are presented using specific examples. For example, audio content (and in particular music) is described as an example of one form of media consumption. As another example, running is described as one example of a repetitive-motion activity. However, it should be understood that the same concepts are equally applicable to other forms of media consumption and to other forms of repetitive-motion activities, and at least some embodiments include other forms of media consumption and/or other forms of repetitive-motion activities. 
     The users may desire that the media content fits well with the particular repetitive activity. For example, a user who is running may desire to listen to music with a beat that corresponds to the user’s cadence. Beneficially, by matching the beat of the music to the cadence, the user’s performance or enjoyment of the repetitive-motion activity may be enhanced. This desire cannot be met with traditional media-playback devices and media-delivery systems. 
     In general, the present disclosure is directed to a system for managing cadence-based playlists identifying one or more media content items to support a user’s repetitive motion activity. The cadence-based playlists are created to identify media content items having a tempo corresponding to a user’s cadence. The cadence-based playlists can be categorized by different tempo ranges that cover all likely cadences during the user’s activities. A media content item can be added to a cadence-based playlist when a tempo of the media content item falls within a tempo range associated with the cadence-based playlist. A media-playback device is provided to acquire a user’s cadence and retrieve a cadence-based playlist associated with a tempo or a tempo range corresponding to the cadence. The media-playback device operates to play back the retrieved cadence-based playlist while the user performs the repetitive motion activity. 
       FIG.  1    illustrates an example system  100  for managing cadence-based playlists. The example system  100  includes a media-playback device  102  and a media-delivery system  104 . The system  100  communicates across a network  106 . Also shown are a user U who is running, and one or more cadence-based playlists  112 . The user U’s upcoming steps S are shown as well. A step represents a single strike of the runner’s foot upon the ground. 
     The media-playback device  102  operates to play one or more cadence-based playlists  112  to produce media output  110 . In some embodiments, the cadence-based playlists  112  contains a list of media content items that are provided by the media-delivery system  104  and transmitted to the media-playback device  102  using the network  106 . A media content item is an item of media content, including audio, video, or other types of media content, which may be stored in any format suitable for storing media content. Non-limiting examples of media content items include songs, albums, music videos, movies, television episodes, podcasts, other types of audio or video content, and portions or combinations thereof. 
     The media-playback device  102  plays back the cadence-based playlists  112  for the user based on the user’s cadence. In the example shown, the media output  110 , which is generated by playing back the media content items contained in the cadence-based playlist  112 , includes music with a tempo that corresponds to the user’s cadence. The tempo (or rhythm) of music refers to the frequency of the beat and is typically measured in beats per minute (BPM). The beat is the basic unit of rhythm in a musical composition (as determined by the time signature of the music). Accordingly, in the example shown, the user U’s steps occur at the same frequency as the beat of the music. 
     For example, if the user U is running at a cadence of  180  steps per minute, the media-playback device  102  may play a cadence-based playlist  112  containing one or more media content items having a tempo equal to or approximately equal to 180 BPM. In other embodiments, the media-playback device  102  plays a cadence-based playlist  112  containing one or more media content items having a tempo equal or approximately equal to the result of dividing the cadence by an integer such as a tempo that is equal to or approximately equal to one-half (e.g., 90 BPM when the user is running at a cadence of  180  steps per minute), one-fourth, or one-eighth of the cadence. Alternatively, the media-playback device  102  plays a cadence-based playlist  112  containing one or more media content items having a tempo that is equal or approximately equal to an integer multiple (e.g., 2 ×, 4 ×, etc.) of the cadence. Further, in some embodiments, the media-playback device  102  operates to play multiple media content items including one or more media content items having a tempo equal to or approximately equal to the cadence and one or more media content items have a tempo equal or approximately equal to the result of multiplying or dividing the cadence by an integer. Various other combinations are possible as well. 
     As described herein, the cadence-based playlist  112  includes a list of one or more media content items (e.g., music) having a tempo that is within a predetermined range of a target tempo. In at least some embodiments, the predetermined range is plus or minus 2.5 BPM. For example, if the user U is running at a cadence of 180 steps per minute, the media-playback device  102  operates to play a cadence-based playlist  112  containing a list of media content items having a tempo of 177.5-182.5 BPM. Alternatively, in other embodiments, the predetermined range is itself in a range from 1 BPM to 10 BPM. Other ranges of a target tempo are also possible. 
     Further, in some embodiments, the media content items that are played back on the media-playback device  102  have a tempo equal to or approximately equal to a user U’s cadence after it is rounded. For example, the cadence may be rounded to the nearest multiple of 2.5, 5, or 10 and then the media-playback device  102  plays a cadence-based playlist  112  with media content items having a tempo equal to or approximately equal to the rounded cadence. As described herein, the media-playback device  102  uses the cadence to select a cadence-based playlist  112  with a predetermined tempo range of music for playback. For example, if the user U’s cadence is  181  steps per minute, the media-playback device  102  may operate to play a cadence-based playlist  112  from a predetermined tempo range of 180-184.9 BPM; while if the user U’s cadence is 178 steps per minute, the media-playback device  102  may operate to play a cadence-based playlist  112  from a predetermined tempo range of 175-179.9 BPM. 
       FIG.  2    is a schematic illustration of an example system  100  for managing cadence-based playlists. In  FIG.  2   , the media-playback device  102 , the media-delivery system  104 , and the network  106  are shown. Also shown are the user U and a satellite S. 
     As noted above, the media-playback device  102  operates to play media content items. In some embodiments, the media-playback device  102  operates to play media content items that are provided (e.g., streamed, transmitted, etc.) by a system external to the media-playback device such as the media-delivery system  104 , another system, or a peer device. Alternatively, in some embodiments, the media-playback device  102  operates to play media content items stored locally on the media-playback device  102 . Further, in at least some embodiments, the media-playback device  102  operates to play media content items that are stored locally as well as media content items provided by other systems. 
     In some embodiments, the media-playback device  102  is a computing device, handheld entertainment device, smartphone, tablet, watch, wearable device, or any other type of device capable of playing media content. In yet other embodiments, the media-playback device  102  is a laptop computer, desktop computer, television, gaming console, set-top box, network appliance, blue-ray or DVD player, media player, stereo, or radio. 
     In at least some embodiments, the media-playback device  102  includes a location-determining device  150 , a touch screen  152 , a processing device  154 , a memory device  156 , a content output device  158 , a cadence-acquiring device  160 , and a network access device  162 . Other embodiments may include additional, different, or fewer components. For example, some embodiments may include a recording device such as a microphone or camera that operates to record audio or video content. As another example, some embodiments do not include one or more of the location-determining device  150  and the touch screen  152 . 
     The location-determining device  150  is a device that determines the location of the media-playback device  102 . In some embodiments, the location-determining device  150  uses one or more of the following technologies: Global Positioning System (GPS) technology which may receive GPS signals  170  from satellites S, cellular triangulation technology, network-based location identification technology, Wi-Fi positioning systems technology, and combinations thereof. 
     The touch screen  152  operates to receive an input  172  from a selector (e.g., a finger, stylus etc.) controlled by the user U. In some embodiments, the touch screen  152  operates as both a display device and a user input device. In some embodiments, the touch screen  152  detects inputs based on one or both of touches and near-touches. In some embodiments, the touch screen  152  displays a user interface  164  for interacting with the media-playback device  102 . As noted above, some embodiments do not include a touch screen  152 . Some embodiments include a display device and one or more separate user interface devices. Further, some embodiments do not include a display device. 
     In some embodiments, the processing device  154  comprises one or more central processing units (CPU). In other embodiments, the processing device  154  additionally or alternatively includes one or more digital signal processors, field-programmable gate arrays, or other electronic circuits. 
     The memory device  156  operates to store data and instructions. In some embodiments, the memory device  156  stores instructions for a media-playback engine  166  that includes a cadence-based playlist selection engine  168 . 
     The memory device  156  typically includes at least some form of computer-readable media. Computer readable media include any available media that can be accessed by the media-playback device  102 . By way of example, computer-readable media include computer readable storage media and computer readable communication media. 
     Computer readable storage media includes volatile and nonvolatile, removable and non-removable media implemented in any device configured to store information such as computer readable instructions, data structures, program modules, or other data. Computer readable storage media includes, but is not limited to, random access memory, read only memory, electrically erasable programmable read only memory, flash memory and other memory technology, compact disc read only memory, blue ray discs, digital versatile discs or other optical storage, magnetic cassettes, magnetic tape, magnetic disk storage or other magnetic storage devices, or any other medium that can be used to store the desired information and that can be accessed by the media-playback device  102 . In some embodiments, computer readable storage media is non-transitory computer readable storage media. 
     Computer readable communication media typically embodies computer readable instructions, data structures, program modules or other data in a modulated data signal such as a carrier wave or other transport mechanism and includes any information delivery media. The term “modulated data signal” refers to a signal that has one or more of its characteristics set or changed in such a manner as to encode information in the signal. By way of example, computer readable communication media includes wired media such as a wired network or direct-wired connection, and wireless media such as acoustic, radio frequency, infrared, and other wireless media. Combinations of any of the above are also included within the scope of computer readable media. 
     The content output device  158  operates to output media content. In some embodiments, the content output device  158  generates media output  110  for the user U. Examples of the content output device  158  include a speaker, an audio output jack, a Bluetooth transmitter, a display panel, and a video output jack. Other embodiments are possible as well. For example, the content output device  158  may transmit a signal through the audio output jack or Bluetooth transmitter that can be used to reproduce an audio signal by a connected or paired device such as headphones or a speaker. 
     The cadence-acquiring device  160  operates to acquire a cadence associated with the user U. In at least some embodiments, the cadence-acquiring device  160  operates to determine cadence directly and includes one or more accelerometers or other motion-detecting technologies. Alternatively, the cadence-acquiring device  160  operates to receive data representing a cadence associated with the user U. For example, in some embodiments, the cadence-acquiring device  160  operates to receive data from a watch, bracelet, foot pod, chest strap, shoe insert, anklet, smart sock, bicycle computer, exercise equipment (e.g., treadmill, rowing machine, stationary cycle), or other device for determining or measuring cadence. Further, in some embodiments, the cadence-acquiring device  160  operates to receive a cadence value input by the user U or another person. 
     The network access device  162  operates to communicate with other computing devices over one or more networks, such as the network  106 . Examples of the network access device include wired network interfaces and wireless network interfaces. Wireless network interfaces includes infrared, BLUETOOTH® wireless technology, 802.1 1a/b/g/n/ac, and cellular or other radio frequency interfaces in at least some possible embodiments. 
     The media-playback engine  166  operates to play back one or more of the media content items (e.g., music) to encourage the running of the user U. As described herein, the media-playback engine  166  is configured to communicate with the media-delivery system  104  to receive one or more media content items (e.g., through the stream media  218 ) based on a cadence detected by the cadence-acquiring device  160 . In other embodiments, the media-playback engine  166  is configured to playback one or more media content items that are locally stored in the media-playback device  102 . 
     The cadence-based playlist selection engine  168  operates to retrieve one or more cadence-based playlists  112  based on a cadence of the user U acquired by the media-playback device  102 . An example operation of the cadence-based playlist selection engine  168  is illustrated and described in more detail with reference to  FIGS.  3 - 10   . 
     The network  106  is an electronic communication network that facilitates communication between the media-playback device  102  and the media-delivery system  104 . An electronic communication network includes a set of computing devices and links between the computing devices. The computing devices in the network use the links to enable communication among the computing devices in the network. The network  106  can include routers, switches, mobile access points, bridges, hubs, intrusion detection devices, storage devices, standalone server devices, blade server devices, sensors, desktop computers, firewall devices, laptop computers, handheld computers, mobile telephones, and other types of computing devices. 
     In various embodiments, the network  106  includes various types of links. For example, the network  106  can include wired and/or wireless links, including Bluetooth, ultra-wideband (UWB), 802.11, ZigBee, cellular, and other types of wireless links. Furthermore, in various embodiments, the network  106  is implemented at various scales. For example, the network  106  can be implemented as one or more local area networks (LANs), metropolitan area networks, subnets, wide area networks (such as the Internet), or can be implemented at another scale. Further, in some embodiments, the network  106  includes multiple networks, which may be of the same type or of multiple different types. 
     The media-delivery system  104  comprises one or more computing devices and operates to provide media content items to the media-playback devices  102  and, in some embodiments, other media-playback devices as well. The media-delivery system  104  includes a media server  180  and a repetitive-motion activity server  182 . In at least some embodiments, the media server  180  and the repetitive-motion activity server  182  are provided by separate computing devices. In other embodiments, the media server  180  and the repetitive-motion activity server  182  are provided by the same computing devices. Further, in some embodiments, one or both of the media server  180  and the repetitive-motion activity server  182  are provided by multiple computing devices. For example, the media server  180  and the repetitive-motion activity server  182  may be provided by multiple redundant servers located in multiple geographic locations. 
     The media server  180  operates to transmit stream media  218  to media-playback devices such as the media-playback device  102 . In some embodiments, the media server  180  includes a media server application  184 , a processing device  186 , a memory device  188 , and a network access device  190 . The processing device  186 , memory device  188 , and network access device  190  may be similar to the processing device  154 , memory device  156 , and network access device  162  respectively, which have each been previously described. 
     In some embodiments, the media server application  184  operates to stream music or other audio, video, or other forms of media content. The media server application  184  includes a media stream service  194 , a media data store  196 , and a media application interface  198 . The media stream service  194  operates to buffer media content such as media content items  206 ,  208 , and  210 , for streaming to one or more streams  200 ,  202 , and  204 . 
     The media application interface  198  can receive requests or other communication from media-playback devices or other systems, to retrieve media content items from the media server  180 . For example, in  FIG.  2   , the media application interface  198  receives communication  234  from the media-playback engine  166 . 
     In some embodiments, the media data store  196  stores media content items  212 , media content metadata  214 , and playlists  216 . The media data store  196  may comprise one or more databases and file systems. Other embodiments are possible as well. As noted above, the media content items  212  may be audio, video, or any other type of media content, which may be stored in any format for storing media content. 
     The media content metadata  214  operates to provide various information associated with the media content items  212 . In some embodiments, the media content metadata  214  includes one or more of title, artist name, album name, length, genre, mood, era, etc. The playlists  216  operate to identify one or more of the media content items  212 . In some embodiments, the playlists  216  identify a group of the media content items  212  in a particular order. In other embodiments, the playlists  216  merely identify a group of the media content items  212  without specifying a particular order. Some, but not necessarily all, of the media content items  212  included in a particular one of the playlists  216  are associated with a common characteristic such as a common genre, mood, or era. Examples of the playlists  216  is illustrated and described in more detail with respect to  FIGS.  5 - 7   . 
     The repetitive-motion activity server  182  operates to provide repetitive-motion activity-specific information about media content items to media-playback devices. In some embodiments, the repetitive-motion activity server  182  includes a repetitive-motion activity server application  220 , a processing device  222 , a memory device  224 , and a network access device  226 . The processing device  222 , memory device  224 , and network access device  226  may be similar to the processing device  154 , memory device  156 , and network access device  162  respectively, which have each been previously described. 
     In some embodiments, repetitive-motion activity server application  220  operates to transmit information about the suitability of one or more media content items for playback during a particular repetitive-motion activity. The repetitive-motion activity server application  220  includes a repetitive-motion activity interface  228  and a repetitive-motion activity media metadata store  230 . 
     In some embodiments, the repetitive-motion activity server application  220  may provide one or more cadence-based playlists  112  at a particular tempo (or a particular range of tempo) to a media-playback device in response to a request that includes a particular cadence value. Further, in some embodiments, the media content items included in the returned list will be particularly relevant for the repetitive motion activity in which the user is engaged (for example, if the user is running, the returned list of media content items may include only media content items that have been identified as being highly runnable). 
     The repetitive-motion activity interface  228  operates to receive requests or other communication from media-playback devices or other systems to retrieve information about media content items from the repetitive-motion activity server  182 . For example, in  FIG.  2   , the repetitive-motion activity interface  228  receives communication  236  from the media-playback engine  166 . 
     In some embodiments, the repetitive-motion activity media metadata store  230  stores repetitive-motion activity media metadata  232 . The repetitive-motion activity media metadata store  230  may comprise one or more databases and file systems. Other embodiments are possible as well. 
     The repetitive-motion activity media metadata  232  operates to provide various information associated with media content items, such as the media content items  212 . In some embodiments, the repetitive-motion activity media metadata  232  provides information that may be useful for selecting media content items for playback during a repetitive-motion activity. For example, in some embodiments, the repetitive-motion activity media metadata  232  stores runnability scores for media content items that corresponds to the suitability of particular media content items for playback during running. As another example, in some embodiments, the repetitive-motion activity media metadata  232  stores timestamps (e.g., start and end points) that identify portions of a media content items that are particularly well-suited for playback during running (or another repetitive-motion activity). 
     As described herein, some embodiments of the repetitive-motion activity media metadata  232  include information about the cadence-based playlists  112  associated with different tempo ranges. An example of such repetitive-motion activity media metadata  232  is illustrated and described in more detail with reference to  FIG.  9   . 
     Each of the media-playback device  102  and the media-delivery system  104  can include additional physical computer or hardware resources. In at least some embodiments, the media-playback device  102  communicates with the media-delivery system  104  via the network  106 . 
     Although in  FIG.  2    only a single media-playback device  102  and media-delivery system  104  are shown, in accordance with some embodiments, the media-delivery system  104   can support the simultaneous use of multiple media-playback devices, and the media-playback device can simultaneously access media content from multiple media-delivery systems. Additionally, although  FIG.  2    illustrates a streaming media based system for a cadence-based playlists management system, other embodiments are possible as well. For example, in some embodiments, the media-playback device  102  includes a media data store  196  and the media-playback device  102  is configured to perform cadence-based playlists management without accessing the media-delivery system  104 . Further in some embodiments, the media-playback device  102  operates to store previously streamed media content items in a local media data store. 
     In at least some embodiments, the media-delivery system  104  can be used to stream, progressively download, or otherwise communicate music, other audio, video, or other forms of media content items to the media-playback device  102  based on a cadence acquired by the cadence-acquiring device  160  of the media-playback device  102 . In accordance with an embodiment, a user U can direct the input  172  to the user interface  164  to issue requests, for example, to playback media content corresponding to the cadence of a repetitive motion activity on the media-playback device  102 . 
       FIG.  3    illustrates an example method  300  of managing cadence-based playlists with the system  100 . In some embodiments, the method  300  includes operations  302  and  304 . 
     At the operation  302 , one or more cadence-based playlists  112  are created to identify one or more media content items that are selected based on tempo thereof. An example of the operation  302  is described in more detail with reference to  FIG.  4   . 
     At the operation  304 , the media-playback device  102  operates to acquire a user’s cadence and select one or more of the cadence-based playlists  112  for playback. An example of the operation  304  is described in more detail with reference to  FIG.  10   . 
       FIG.  4    illustrates an example method  310  for performing the operation  302  of  FIG.  3   . In some embodiments, the method  310  includes operations  312 ,  314 ,  316 , and  318 . 
     In other embodiments, the operations of the method  310  can be performed in different orders. In yet other embodiments, the method  310  includes additional operations. In yet other embodiments, the method  310  includes only one or some of the operations  312 ,  314 ,  316 , and  318 . 
     At the operation  312 , one or more media content items are maintained in the media data store  196  of the media server  180 . 
     At the operation  314 , one or more cadence-based playlists  112  are created to identify media content items with different tempi. For example, a cadence-based playlist  112  is configured with a tempo of 150 BPM so that a media content item having the same tempo (or a tempo similar to 150 BPM) is identified by that playlist  112 . In other embodiments, the cadence-based playlists  112  are characterized with different ranges of tempo so that one or more media content items having a tempo within a particular range of tempo are identified by the cadence-based playlists  112  associated with that range of tempo. For example, where a cadence-based playlist  112  is characterized to have a range of 150-155 BPM, one or more media content items having a tempo between 150-155 BPM are to be identified by the cadence-based playlist  112 . 
     At the operation  316 , the media content items are analyzed to identify a tempo thereof. A tempo of a media content item can be determined in various known manners. In the example of songs, a tempo of a song can be relatively easily identified because songs typically have a steady tempo throughout their entire playing time. Where a tempo changes significantly throughout a song, in some embodiments, such variations in tempo can be averaged to represent a single tempo of the song. In other examples, a portion of the song having an approximately constant tempo can be identified, and such a constant tempo can be used as a tempo for the entire song. In yet other examples, the portion of the song having an approximately constant tempo is taken and used to replace the entire song while the other portion of the song, which has variable tempo, are excluded from playback. Other methods of obtaining a tempo of a song are also possible. 
     At the operation  318 , the media content items are associated with the cadence-based playlists  112  based on tempo. By way of example, a media content item having a tempo of 132 BPM is associated with a cadence-based playlist  112  characterized with a tempo range of 130-135 BPM so that the cadence-based playlist  112  with the range of 130-135 BPM identifies the media content item having 132 BPM for playback. 
     Referring to  FIGS.  5 - 7   , examples of the playlists  214  are described with different structures. In particular,  FIG.  5    schematically illustrates an example of the playlists  214  maintained in the media-delivery system  104 ,  FIG.  6    schematically illustrates another example of the playlists  214 , and  FIG.  7    schematically illustrates yet another example of the playlists  214 . In these examples, the cadence-based playlists  112  are included in the playlists  214 . 
     As illustrated in  FIGS.  5 - 7   , in some embodiments, the playlists  216  can be categorized by different characteristics so that at least some of the playlists  216  are grouped into one or more sets of playlists. In the illustrated example, the playlists  216  includes a set of genre-specific playlists  322 , a set of theme-specific playlists  324 , a set of era-specific playlists  326 , and other sets of playlists with suitable characteristics. In other embodiments, the playlists  216  include playlists created by users for various purposes, such as personal use or sharing. 
     The genre-specific playlists  322  are configured to identify media content items characterized with different genres, such as hip hop, pop, country, electronic, folk, R&amp;B and soul, rock, Latin, African, Asian, Avant-garde, blues, comedy, and any other genres. In the illustrated example, the genre-specific playlists  322  include a subset of hip hop playlists  332 , a subset of country playlists  334 , and other subsets of playlists with suitable genre-related characteristics. In some embodiments, as illustrated in  FIG.  5   , each of the subsets of genre-related playlists (including subsets of playlists  332  and  334 ) includes one or more cadence-based playlists  112 . 
     The theme-specific playlists  324  are configured to identify media content items characterized with different themes of a repetitive motion activity. The themes of activity can be categorized by time, place, speed, type, and/or any other suitable conditions. By way of example, the themes of running can be divided into morning run, afternoon run, evening run, and night run (by time), into riverside run, beachside run, mountain run, rural run, and city run (by place), or into sprinting, jogging, and walking (by speed). In the illustrated example, the theme-specific playlists  324  include a subset of morning run playlists  336 , a subset of afternoon run playlists  338 , and other subsets of playlists with suitable theme-related characteristics. In some embodiments, as illustrated in  FIG.  5   , each of the subsets of theme-related playlists (including subsets of playlists  336  and  338 ) includes one or more cadence-based playlists  112 . 
     The era-specific playlists  326  are configured to identify media content items characterized with different eras. By way of examples, songs can be divided into different eras, such as 50 s, 60 s, 70 s, 80 s, 90 s, 2000 s, and 2010 s. In the illustrated example, the era-specific playlists  326  include a subset of 90 s playlists  340 , a subset of 80 s playlists, and other subsets of playlists of different eras. In some embodiments, as illustrated in  FIG.  5   , each of the subsets of era-related playlists (including subsets of playlists  340  and  342 ) includes one or more cadence-based playlists  112 . 
     In some embodiments, at least one media content item can be identified by a plurality of playlists of the same characteristic. In other embodiments, at least one media content item can be identified by a plurality of playlists of different characteristics. In yet other embodiments, at least one media content item can be identified exclusively by a single playlist. 
     In some embodiments, as illustrated in  FIG.  5   , the playlists  216  are organized hierarchically with the cadence-based playlists  112  contained in the subsets of playlists (such as  332 ,  334 ,  336 ,  338 ,  340 , and  342 ). In other embodiments, it is also possible to differently categorize the playlists  216  including the cadence-based playlists  112 . In some examples, as illustrated in  FIG.  6   , the cadence-based playlists  112  are organized in parallel with other playlists (e.g., the genre-specific playlists  332 , the theme-specific playlists  324 , and the era-specific playlists  326 ) of different characteristics. In other examples, as illustrated in  FIG.  7   , the cadence-based playlists  112  are organized to include one or more subsets of playlists (e.g., the genre-specific playlists  332 , the theme-specific playlists  324 , and the era-specific playlists  326 ) of different characteristics. 
       FIG.  8    illustrates an example structure of the cadence-based playlist  112 . In some embodiments, the cadence-based playlist  112  includes various attributes, such as a playlist ID  360 , a playlist name  362 , playlist characteristics  364 , a tempo range  366 , and a list of tracks  368 . In other embodiments, the cadence-based playlist  112  can include other attributes. In yet other embodiments, the cadence-based playlist  112  can include only some of the illustrated attributes, either in addition to other attributes or without additional attributes. 
     The playlist ID  360  is used to identify a cadence-based playlist  112  associated with the playlist ID  360 . 
     The playlist name  362  represents the name of the cadence-based playlist  112 . In some embodiments, the playlist name  362  is displayed on the media-playback device  102  so that the user U identifies the cadence-based playlist  112  for various operations, such as playing back the cadence-based playlist  112 . In some embodiments where the cadence-based playlists  112  are categorized within parent playlists, such as the characteristic-related playlists (e.g. the genre-specific playlists  322 , the theme-specific playlists  324 , and the era-specific playlists  326 ) as illustrated in  FIG.  5   , the cadence-based playlists  112  do not need to have the playlist name  326  because the cadence-based playlists  112  can be identified by their parent playlist’s names. 
     The playlist characteristics  364  are used to identify various characteristics of the cadence-based playlist  112 . As described above, examples of such characteristics include genres, themes, eras, and other suitable characteristics of playlists or media content items. 
     The tempo range  366  is configured to identify a range of tempo associated with the cadence-based playlist  112 . Based on the tempo range  366 , the cadence-based playlist  112  is configured to identify one or more media content items having a tempo that falls within the tempo range  366 . In other embodiments, the cadence-based playlist  112  has a single value of tempo, and is configured to identify one or more media content items having the same or similar tempo. 
     The tempo range  366  can be determined in various manners. In some embodiments, the tempo ranges  366  are defined at predetermined intervals. By way of example, the tempo ranges  366  can increase by 5 BPM (e.g., 130-135, 135-140, 140-145, 145-150, 150-155, 155-160, etc.). In other examples, the tempo ranges  366  are set by 10 BPM (e.g., 130-140, 140-150, 150-160, etc.). Other intervals are also possible. In some embodiments, the tempo ranges  366  are determined to cover all possible cadences during user’s repetitive motion activities (e.g., running). 
     The list of tracks  368  identifies one or more media content items to be played back when the cadence-based playlist  112  is selected based on a user’s cadence. The media content items contained in the list of tracks  368  of the cadence-based playlist  112  have a tempo that falls within the tempo range  366  of the cadence-based playlist  112 . In some embodiments, a number of media content items that are identified by the cadence-based playlist  112  is determined to be sufficient to play back during the entire repetitive motion activity by a user. For example, a cadence-based playlist  112  is configured to contain a sufficient number of tracks (e.g., 10, 15, or 20 tracks) to play about an hour. In other examples, a cadence-based playlist  112  is designed to play back more than an hour. In yet other examples, a cadence-based playlist  112  is configured to play back less than an hour. 
     In some embodiments, a user U can manually edit a cadence-based playlist  112  to add or remove one or more content media items into the list of tracks  368 . In some embodiments, the user U can only add content media items having a tempo within the tempo range  366  of the cadence-based playlist  112 . In other embodiments, the content media items that are manually added can have a tempo outside the tempo range  366  of the cadence-based playlist  112 . 
       FIG.  9    is an example data structure of the repetitive-motion activity media metadata  232 . The media metadata  232  can include information about the playlists  216  including the cadence-based playlists  112 . In some embodiments, the media metadata  232  contain a playlist ID column  380 , a tempo column  382 , and one or more playlist characteristics columns  384 . In other embodiments, the media metadata  232  can be structured in different manners. 
     The playlist ID column  380  is used to identify each cadence-based playlist  112 . In some embodiments, attributes in the playlist ID column  380  are associated with the playlist ID  360  of the cadence-based playlists  112 . 
     The tempo column  382  is used to identify the tempo ranges  366  associated with the cadence-based playlists  112 . Attributes in the tempo column  382  can be determined as described above. 
     The playlist characteristics columns  384  are used to identify the characteristics of the playlists  112 , such as genres, themes, eras, and any other characteristics. 
     In other embodiments, the media metadata  232  further include a parent playlist column. The parent playlist column is used to identify playlists (e.g., characteristic-based playlists, such as the genre-specific playlists  322 , the theme-specific playlists  324 , and the era-specific playlists  326 ) that is parents of the cadence-based playlists  112 . 
       FIG.  10    is a flowchart illustrating an example method  400  of performing the operation  304  of  FIG.  3   . In some embodiments, the method  400  includes operations  402 ,  404 ,  406 ,  408 ,  410 ,  412 ,  414 ,  416 ,  418 , and  420 . In some embodiments, the method  400  is performed using the media-playback device  102 . In other embodiments, one or more other computing devices can be used to execute the method  400 . 
     In other embodiments, the operations of the method  400  can be performed in different orders. In yet other embodiments, the method  400  includes additional operations. In yet other embodiments, the method  400  includes only one or some of the operations  402 ,  404 ,  406 ,  408 ,  410 ,  412 ,  414 ,  416 ,  418 , and  410 . 
     At the operation  402 , the media-playback device  102  operates to receive a user selection of one or more playlist characteristics. As described herein, examples of such playlist characteristics include genre, theme, and era. In some embodiments, the media-playback device  102  operates to prompt a user to input the playlist characteristics. For example, the media-playback device  102  can provide a user interface (e.g., a GUI displayed on a touch-sensitive screen) for a user to interact to enter one or more playlist characteristics (e.g., genre) that the user wants to play during a repetitive motion activity (e.g., running). By way of example, before starting running, a user can select a genre of music to which the user wants to listen while the user is running. 
     At the operation  404 , the media-playback device  102  operates to acquire a user’s cadence. In some embodiments, the user’s cadence is automatically obtained or detected by the media-playback device  102  as the user performs a repetitive motion activity. For example, as a user begins running, the media-playback device  102  detects the user’s repetitive motion and calculates the cadence thereof. 
     In other embodiments, the user’s cadence can be manually set before or during the repetitive motion activity. In some examples, the user’s cadence can be acquired by prompting a user to select a cadence (i.e., the frequency of the user’s repetitive motion) that the user wants to perform during a repetitive motion activity. In other examples, the user’s cadence can be acquired by prompting the user to select a tempo (i.e., the frequency of beat in media content items) of a playlist or media content items that the user wants to play back during a repetitive motion activity. 
     At the operation  406 , the media-playback device  102  determines a tempo corresponding to the acquired cadence. In some embodiments, a relationship between a tempo and a cadence, as described herein, is used to convert the acquired cadence to a corresponding tempo. 
     At the operation  408 , the media-playback device  102  operates to retrieve a cadence-based playlist  112  that has a tempo range  366  within which the tempo corresponding to the acquired cadence falls, and the playlist characteristics selected by the user. By way of example, where the user has selected a hip hop music playlist (at the operation  402 ) and a tempo corresponding to the user’s cadence is determined to be about 163 BPM, the media-playback device  102  can retrieve a cadence-based playlist  112  having a genre of hip hop and a tempo range of 160-165 BPM. 
     In some embodiments, the media-playback device  102  sends a request for the media metadata  232  to the media-delivery system  104 , and receives the media metadata  232  from the media-delivery system  104  that transmits it to the media-playback device  102  in response to the request. As some embodiments of the media metadata  232  (as shown in  FIG.  9   ) contain the playlist characteristics information as well as the tempo information, the media-playback device  102  can look up the media metadata  232  and select a proper cadence-based playlist  112  having the selected playlist characteristics (at the operation  402 ) and the tempo corresponding to the acquired cadence. In other embodiments, where the media-playback device  102  can retrieve one or more cadence-based playlists  112  based on the selected playlist characteristics and the determined tempo (or cadence) from the media-playback device  102  where the cadence-based playlists  112  are stored in the media-playback device  102 . 
     At the operation  410 , once a cadence-based playlist  112  corresponding to the acquired cadence has been retrieved, the media-playback device  102  operates to play back the retrieved cadence-based playlist  112  while the user continues to perform the repetitive motion activity. As described herein, the cadence-based playlist  112  identifies one or more media content items having a tempo within the tempo range of the cadence-based playlist  112 . Thus, the media-playback device  102  plays back the media content items having a tempo identical to, or similar to, the tempo corresponding to the user’s cadence. 
     At the operation  412 , the media-playback device  102  determines whether a cadence has changed beyond a predetermined threshold. Similar to the operation  404 , the media-playback device  102  can operate to acquire any change in the user’s cadence. In some embodiments, the media-playback device  102  continues to automatically monitor and detect the user’s cadence during the repetitive motion activity. In other embodiments, a cadence can change manually by a user who adjusts it (or by adjusting a tempo) in the middle of the repetitive motion activity. 
     In some embodiments, the predetermined threshold is determined based on the tempo range of the cadence-based playlist  112  that is currently played. In addition, the predetermined threshold is determined based on duration of change in the user’s cadence. For example, if the cadence has changed to fall outside the tempo range of the current cadence-based playlist  112  for a predetermined amount of time, it is determined that the cadence has changed beyond the predetermined threshold. By way of example, if the media-playback device  102  is playing back a cadence-based playlist  112  having a tempo range of 150-155 BPM and detects the user’s cadence has changed to 166 BPM more than one minutes, then it is considered that the cadence has exceeded the predetermined threshold. 
     If it is determined that the cadence has not changed beyond the predetermined threshold (“NO” at the operation  412 ), the method  400  stays at the operation  410  to continue to play back the current cadence-based playlist  112 . Otherwise (“YES” at the operation  412 ), the method  400  moves on to the operation  414 . 
     At the operation  414 , the media-playback device  102  determines whether the user has locked the current tempo. In some embodiments, the user can select a certain tempo or cadence to maintain the selected tempo or cadence throughout the entire repetitive motion activity (or at least a portion thereof). If the current tempo has been set to be consistent (“YES” at the operation  414 ), the method  400  stays at the operation  410  to continue to play back the current cadence-based playlist  112 . If not (“NO” at the operation  414 ), the method  400  moves on to the operation  416 . 
     At the operation  416 , the media-playback device  102  determines whether the user’s cadence changes below a predetermined level. In some embodiments, the media-playback device  102  is configured to cease to play back media content items if the user stops performing the activity or performs the activity with a cadence lower than a preset level (e.g., when a user stops running temporarily or permanently, or runs slowly). By way of example, if the user runs with a cadence less than 15 BPM, the media-playback device  102  can be configured to stop playing back any playlist. Other examples are also possible. 
     If it is determined that the user’s cadence changes below a predetermined level (“YES” at the operation  416 ), the method  400  moves on to the operation  418 , in which the media-playback device  102  pauses or stops playing back the playlist  112 . If not (“NO” at the operation  416 ), the method  400  returns to the operation  406  to determine a tempo corresponding to the new cadence. Then, the subsequent operations follow, as described above, to play back another cadence-based playlist  112  corresponding to the new cadence. 
     At the operation  420 , after stopping playing back a playlist, the media-playback device  102  determines whether a cadence has changed to be equal to, or above, the predetermined level as described in the operation  416 . If so (“YES” at the operation  420 ), the method  400  returns to the operation  406 , in which the media-playback device  102  operates to determine a tempo corresponding to the new cadence. Then, the subsequent operations follow, as described above, to play back another cadence-based playlist  112  corresponding to the new cadence. If it is determined that a cadence has not changed to the predetermined level, the method  400  stays at the operation  418  to continue to stop playing back a playlist. 
     As noted previously, although many of the examples provided above are described with respect to running, other embodiments relate to other repetitive motion activities as well such as cycling, swimming, and rowing. 
     As used herein, “about” refers to a degree of deviation based on experimental error typical for the particular property identified. The latitude provided the term “about” will depend on the specific context and particular property and can be readily discerned by those skilled in the art. The term “about” is not intended to either expand or limit the degree of equivalents which may otherwise be afforded a particular value. Further, unless otherwise stated, the term “about” shall expressly include “exactly,” consistent with the discussions regarding ranges and numerical data. It is to be understood that a numerical range is used merely for convenience and brevity and thus should be interpreted flexibly to include not only the numerical values explicitly recited as the limits of the range, but also to include all the individual numerical values or sub-ranges encompassed within that range as if each numerical value and sub-range is explicitly recited. As an illustration, a numerical range of “about 4 percent to about 7 percent” should be interpreted to include not only the explicitly recited values of about 4 percent to about 7 percent, but also include individual values and sub-ranges within the indicated range. Thus, included in this numerical range are individual values such as 4.5, 5.25 and 6 and sub-ranges such as from 4-5, from 5-7, and from 5.5-6.5; etc. This same principle applies to ranges reciting only one numerical value. Furthermore, such an interpretation should apply regardless of the breadth of the range or the characteristics being described. 
     The various examples and teachings described above are provided by way of illustration only and should not be construed to limit the scope of the present disclosure. Those skilled in the art will readily recognize various modifications and changes that may be made without following the example examples and applications illustrated and described herein, and without departing from the true spirit and scope of the present disclosure.