Systems and methods for adaptive streaming of multimedia content

The disclosed computer-implemented method includes determining that audio quality is to be adjusted for a multimedia streaming connection over which audio data and video data are being streamed to a content player. The audio data is streamed at a specified audio quality level and the video data is streamed at a specified video quality level. The method also includes determining that a specified minimum video quality level is to be maintained while adjusting the audio quality level. Still further, the method includes dynamically adjusting the audio quality level of the multimedia streaming connection while maintaining the video quality level of the multimedia streaming connection at at least the specified minimum video quality level. Various other methods, systems, and computer-readable media are also disclosed.

BACKGROUND

Digital content distribution systems may provide a variety of different types of content (e.g., tv shows, movies, etc.) to end users. This content may include both audio and video data and may be sent to a user's content player as a multimedia stream. The quality of video content within a multimedia stream may be dependent on, among other things, a content player's network connection with a content distribution system. For instance, if a user streams a movie over a network connection with a content provider, that movie may be streamed at a rate dictated primarily by the bandwidth currently available on the network connection. Throughout the stream, the content provider may vary the encoding quality of the video data based on the available bandwidth. In contrast, audio data in the stream is typically provided at a single, fixed bit rate.

SUMMARY

As will be described in greater detail below, the present disclosure describes methods and systems for dynamically adjusting audio quality level in a multimedia streaming connection.

In one example, a computer-implemented method for adaptively streaming multimedia content includes determining that audio quality is to be adjusted for a multimedia streaming connection over which audio data and video data are being streamed to a content player, where the audio data is streamed at a specified audio quality level and the video data is streamed at a specified video quality level. The method further includes determining that a specified minimum video quality level is to be maintained while adjusting the audio quality level, and dynamically adjusting the audio quality level of the multimedia streaming connection while maintaining the video quality level of the multimedia streaming connection at at least the specified minimum video quality level.

In one example, dynamically adjusting the audio quality level comprises increasing the audio quality level. In some cases, the audio quality level is automatically increased to subsequent higher quality levels until the video quality level reaches a specified quality level that is higher quality than the specified minimum video quality level. In some examples, the audio quality level is adjusted according to a specified bitrate ladder. In some examples, the audio quality level is dynamically adjusted according to one or more user preferences, the user preferences indicating whether audio or video is to be prioritized in the multimedia streaming connection.

In some examples, the method further includes determining that the content player is operating on a specified electronic device, identifying various audio or video hardware capabilities of the specified electronic device, and dynamically adjusting the audio quality level of the multimedia streaming connection according to the audio or video capabilities of the specified electronic device. In some examples, the audio quality level is dynamically adjusted for multiple different types of electronic devices. In some examples, the audio data rate at which the audio data is transmitted over the multimedia streaming connection is varied based on a cache size associated with the specified electronic device.

In some examples, dynamically adjusting the audio quality level involves decreasing the audio quality level. In some cases, the audio quality level is dynamically decreased upon determining that network bandwidth for the multimedia streaming connection has dropped below a specified amount. In some examples, the video data corresponds to a movie or television show and, in such cases, the audio quality level is dynamically decreased upon determining that an audio track associated with the movie or television show is substantially silent for at least a minimum specified period of time.

In some examples, the video quality level is prioritized over the audio quality level in the multimedia streaming connection. As such, the audio quality level is dynamically reduced to maintain a specified minimum video quality level. In some examples, the bit rate associated with the audio data in the multimedia streaming connection is varied dynamically based on underlying content associated with the audio data.

In some examples, the method further includes, prior to streaming data through the multimedia streaming connection, determining a startup delay that would be incurred if a higher audio bitrate were to be used to stream the audio data. In some examples, the audio and video data are streamed to the content player according to margin curves. In some cases, the audio quality level is dynamically adjusted for multiple different audio data streams that are part of the multimedia streaming connection.

In some examples, the method further includes analyzing various portions of prior transmission data associated with audio and video data transferred during the multimedia streaming connection, predicting a future amount of audio and video data that will be transferred using the multimedia streaming connection, and dynamically adjusting the audio quality level based on the predicted future amount of audio and video data that is to be transferred using the multimedia streaming connection. In some examples, the method further includes locking the audio quality level at a specified level for at least a minimum amount of time after the dynamic adjustment.

In addition, a corresponding system for dynamically adjusting a multimedia data stream includes several modules stored in memory, including at least one physical processor and physical memory comprising computer-executable instructions that, when executed by the physical processor, cause the physical processor to: determine that audio quality is to be adjusted for a multimedia streaming connection over which audio data and video data are being streamed to a content player, where the audio data is streamed at a specified audio quality level and the video data is streamed at a specified video quality level, determine that a specified minimum video quality level is to be maintained while adjusting the audio quality level, and dynamically adjust the audio quality level of the multimedia streaming connection while maintaining the video quality level of the multimedia streaming connection at at least the specified minimum video quality level.

In some examples, the above-described method is encoded as computer-readable instructions on a computer-readable medium. For example, a computer-readable medium includes one or more computer-executable instructions that, when executed by at least one processor of a computing device, cause the computing device to determine that audio quality is to be adjusted for a multimedia streaming connection over which audio data and video data are being streamed to a content player, where the audio data is streamed at a specified audio quality level and the video data is streamed at a specified video quality level, determine that a specified minimum video quality level is to be maintained while adjusting the audio quality level, and dynamically adjust the audio quality level of the multimedia streaming connection while maintaining the video quality level of the multimedia streaming connection at at least the specified minimum video quality level.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

As will be explained in greater detail below, the systems and methods described herein are generally directed to dynamically adjusting bit rates of multimedia content streams, such as audio-video streams. In conventional multimedia streams, audio data is encoded and streamed at a fixed bit rate. Unfortunately, using fixed bit-rate audio within a multimedia stream has various drawbacks. For example, in some cases, a stereo mix is adequate at a particular bit rate (e.g., 192 kilobits per second (kbps)), but a surround mix encoded at the same bit rate may have audible artifacts, reduced soundstage imaging, and/or audible degradation at high frequencies. As another example, fixed bit-rate audio streams do not adapt to changing network conditions and could cause unnecessary audio and/or video rebuffering. These types of audio-related issues have become more common as content providers produce increasingly complex audio mixes with tight levels between dialog, music, and effects elements. In other words, the creative choices of content providers are pushing and exceeding the limits of existing audio encoding and transmission approaches.

One traditional solution to improving audio quality in streaming content is to encode audio at higher fixed bitrates. Unfortunately, while using higher fixed rates for streaming audio addresses some of these drawbacks, in many situations an increase in an audio bit rate actually decreases the quality of a user's overall experience. For example, increasing a Dolby Digital Plus (DD+) stream from 192 kbps to 256 kbps would result in longer start times and undesirable rebuffering for users with limited bandwidth. Furthermore, some electronic devices do not support higher bit rates, and streaming high bit-rate audio to such devices causes audible artifacts and other issues.

In contrast, the systems and methods presented herein address deficiencies in existing systems by dynamically adjusting audio bitrates and/or by balancing bitrates of different types of media in a multimedia stream. For example, some of the methods discussed herein increase audio quality (e.g., increase audio bitrate or change to a higher-quality encoding method) without sacrificing video quality or causing additional rebuffering. For instance, in some cases, audio and video are being streamed from a content provider to a client device. The content provider determines that sufficient bandwidth is available to increase the quality or bit rate of the audio. The content provider then increases the bit rate of the audio level to provide a higher quality audio experience. This higher-quality audio experience, however, does not come at the cost of a lower-quality video experience. When adjusting the bit rate of the audio signal, the content provider maintains a minimum video quality level. Thus, if bandwidth drops for some reason, the audio quality will be reduced to maintain the minimum video quality level. In this manner, the quality level of the audio signal is dynamically adjusted to provide the highest quality audio signal whenever possible. However, if the available bandwidth will not allow both a high-quality audio signal and a minimum quality video signal, the audio signal will be adjusted downward so as not to degrade the video quality.

In some situations, implementing adaptive bit-rate audio streaming improves video quality in a multimedia stream. In some cases, for example, an audio stream is downswitched when network throughput drops, thereby freeing bandwidth for the video stream and reducing video rebuffering or downswitching. In another example, an audio stream is downswitched during a period of silence, dialog, or low-complexity audio to allow a video stream to be upswitched or buffered more effectively. Other embodiments establish new encoding profiles for streaming (e.g., encoding profiles with bit rates higher than 192 kbps for DD+streams). Embodiments of this disclosure also provide methods for certification, blacklisting, and whitelisting certain devices for use with adaptive bit-rate audio.

Adaptive audio streaming also provides intermediary bit rates that are not available in traditional streams. For example, if a user has a strong network connection, an adaptive audio system may increase the audio bit rate to over 600 kbps, which provides an audiophile-quality experience. The ability to effectively stream high-quality audio content is a strong differentiator from existing systems and enables content providers to offer additional tiers of content quality in their subscription plan offerings. The systems and methods described herein also provide a variety of other features and advantages that improve computing devices and content streaming.

The following will provide, with reference toFIG. 1, detailed descriptions of exemplary ecosystems for adaptive streaming of multimedia content. The discussion corresponding toFIGS. 2 and 3presents an overview of an exemplary distribution infrastructure and an exemplary content player, respectively. Detailed descriptions of corresponding computer-implemented methods for adaptive streaming of multimedia content will be provided in connection withFIG. 4.

FIG. 1is a block diagram of a content distribution ecosystem100that includes a distribution infrastructure110in communication with a content player120. In some embodiments, distribution infrastructure110is configured to encode data at a specific data rate and to transfer the encoded data to content player120. Content player120is configured to receive the encoded data via distribution infrastructure110and to decode the data for playback to a user. The data provided by distribution infrastructure110includes, for example, audio, video, text, images, animations, interactive content, haptic data, virtual or augmented reality data, location data, gaming data, or any other type of data that is provided via streaming.

Distribution infrastructure110generally represents any services, hardware, software, or other infrastructure components configured to deliver content to end users. For example, distribution infrastructure110includes content aggregation systems, media transcoding and packaging services, network components, and/or a variety of other types of hardware and software. In some cases, distribution infrastructure110is implemented as a highly complex distribution system, a single media server or device, or anything in between. In some examples, regardless of size or complexity, distribution infrastructure110includes at least one physical processor112and at least one memory device114. One or more modules116are stored or loaded into memory114to enable adaptive streaming, as discussed herein.

Content player120generally represents any type or form of device or system capable of playing audio and/or video content that has been provided over distribution infrastructure110. Examples of content player120include, without limitation, mobile phones, tablets, laptop computers, desktop computers, televisions, set-top boxes, digital media players, virtual reality headsets, augmented reality glasses, and/or any other type or form of device capable of rendering digital content. As with distribution infrastructure110, content player120includes a physical processor122, memory124, and one or more modules126. Some or all of the adaptive streaming processes described herein is performed or enabled by modules126, and in some examples, modules116of distribution infrastructure110coordinate with modules126of content player120to provide adaptive streaming of multimedia content.

In certain embodiments, one or more of modules116and/or126inFIG. 1represent one or more software applications or programs that, when executed by a computing device, cause the computing device to perform one or more tasks. For example, and as will be described in greater detail below, one or more of modules116and126represent modules stored and configured to run on one or more general-purpose computing devices. One or more of modules116and126inFIG. 1also represent all or portions of one or more special-purpose computers configured to perform one or more tasks.

In addition, one or more of the modules, processes, algorithms, or steps described herein transform data, physical devices, and/or representations of physical devices from one form to another. For example, one or more of the modules recited herein receive audio data to be encoded, transform the audio data by encoding it, output a result of the encoding for use in an adaptive audio bit-rate system, transmit the result of the transformation to a content player, and render the transformed data to an end user for consumption. Additionally or alternatively, one or more of the modules recited herein transform a processor, volatile memory, non-volatile memory, and/or any other portion of a physical computing device from one form to another by executing on the computing device, storing data on the computing device, and/or otherwise interacting with the computing device.

Physical processors112and122generally represent any type or form of hardware-implemented processing unit capable of interpreting and/or executing computer-readable instructions. In one example, physical processors112and122access and/or modify one or more of modules116and126, respectively. Additionally or alternatively, physical processors112and122execute one or more of modules116and126to facilitate adaptive streaming of multimedia content. Examples of physical processors112and122include, without limitation, microprocessors, microcontrollers, central processing units (CPUs), field-programmable gate arrays (FPGAs) that implement softcore processors, application-specific integrated circuits (ASICs), portions of one or more of the same, variations or combinations of one or more of the same, and/or any other suitable physical processor.

Memory114and124generally represent any type or form of volatile or non-volatile storage device or medium capable of storing data and/or computer-readable instructions. In one example, memory114and/or124stores, loads, and/or maintains one or more of modules116and126. Examples of memory114and/or124include, without limitation, random access memory (RAM), read only memory (ROM), flash memory, hard disk drives (HDDs), solid-state drives (SSDs), optical disk drives, caches, variations or combinations of one or more of the same, and/or any other suitable memory device or system.

FIG. 2is a block diagram of exemplary components of content distribution infrastructure110according to certain embodiments. Distribution infrastructure110includes storage210, services220, and a network230. Storage210generally represents any device, set of devices, and/or systems capable of storing content for delivery to end users. Storage210includes a central repository with devices capable of storing terabytes or petabytes of data and/or includes distributed storage systems (e.g., appliances that mirror or cache content at Internet interconnect locations to provide faster access to the mirrored content within certain regions). Storage210is also configured in any other suitable manner.

As shown, storage210stores, among other items, content212, user data214, and/or log data216. Content212includes television shows, movies, video games, user-generated content, and/or any other suitable type or form of content. User data214includes personally identifiable information (PII), payment information, preference settings, language and accessibility settings, and/or any other information associated with a particular user or content player. Log data216includes viewing history information, network throughput information, and/or any other metrics associated with a user's connection to or interactions with distribution infrastructure110.

Services220includes personalization services222, transcoding services224, and/or packaging services226. Personalization services222personalize recommendations, content streams, and/or other aspects of a user's experience with distribution infrastructure110. Encoding services224compress media at different bitrates which, as described in greater detail below, enable real-time switching between different encodings. Packaging services226package encoded video before deploying it to a delivery network, such as network230, for streaming.

Network230generally represents any medium or architecture capable of facilitating communication or data transfer. Network230facilitates communication or data transfer using wireless and/or wired connections. Examples of network230include, without limitation, an intranet, a wide area network (WAN), a local area network (LAN), a personal area network (PAN), the Internet, power line communications (PLC), a cellular network (e.g., a global system for mobile communications (GSM) network), portions of one or more of the same, variations or combinations of one or more of the same, and/or any other suitable network. For example, as shown inFIG. 2, network230includes an Internet backbone232, an internet service provider234, and/or a local network236. As discussed in greater detail below, bandwidth limitations and bottlenecks within one or more of these network segments triggers video and/or audio bit rate adjustments.

FIG. 3is a block diagram of an exemplary implementation of content player120ofFIG. 1. Content player120generally represents any type or form of computing device capable of reading computer-executable instructions. Content player120includes, without limitation, laptops, tablets, desktops, servers, cellular phones, multimedia players, embedded systems, wearable devices (e.g., smart watches, smart glasses, etc.), smart vehicles, gaming consoles, internet-of-things (IoT) devices such as smart appliances, variations or combinations of one or more of the same, and/or any other suitable computing device.

As shown inFIG. 3, in addition to processor122and memory124, content player120includes a communication infrastructure302and a communication interface322coupled to a network connection324. Content player120also includes a graphics interface326coupled to a graphics device328, an input interface334coupled to an input device336, and a storage interface338coupled to a storage device340.

Communication infrastructure302generally represents any type or form of infrastructure capable of facilitating communication between one or more components of a computing device. Examples of communication infrastructure302include, without limitation, any type or form of communication bus (e.g., a peripheral component interconnect (PCI) bus, PCI Express (PCIe) bus, a memory bus, a frontside bus, an integrated drive electronics (IDE) bus, a control or register bus, a host bus, etc.).

As noted, memory124generally represents any type or form of volatile or non-volatile storage device or medium capable of storing data and/or other computer-readable instructions. In some examples, memory124stores and/or loads an operating system308for execution by processor122. In one example, operating system308includes and/or represents software that manages computer hardware and software resources and/or provides common services to computer programs and/or applications on content player120.

Operating system308performs various system management functions, such as managing hardware components (e.g., graphics interface326, audio interface330, input interface334, and/or storage interface338). Operating system308also provides process and memory management models for playback application310. The modules of playback application310includes, for example, a content buffer312, an audio decoder318, and a video decoder320.

Playback application310is configured to retrieve digital content via communication interface322and play the digital content through graphics interface326. Graphics interface326is configured to transmit a rendered video signal to graphics device328. In normal operation, playback application310receives a request from a user to play a specific title or specific content. Playback application310then identifies one or more encoded video and audio streams associated with the requested title. After playback application310has located the encoded streams associated with the requested title, playback application310downloads sequence header indices associated with each encoded stream associated with the requested title from distribution infrastructure110. A sequence header index associated with encoded content includes information related to the encoded sequence of data included in the encoded content.

In one embodiment, playback application310begins downloading the content associated with the requested title by downloading sequence data encoded to the lowest audio and/or video playback bit rates to minimize startup time for playback. The requested digital content file is then downloaded into content buffer312, which is configured to serve as a first-in, first-out queue. In one embodiment, each unit of downloaded data includes a unit of video data or a unit of audio data. As units of video data associated with the requested digital content file are downloaded to the content player120, the units of video data are pushed into the content buffer312. Similarly, as units of audio data associated with the requested digital content file are downloaded to the content player120, the units of audio data are pushed into the content buffer312. In one embodiment, the units of video data are stored in video buffer316within content buffer312and the units of audio data are stored in audio buffer314of content buffer312.

A video decoder320reads units of video data from video buffer316and outputs the units of video data in a sequence of video frames corresponding in duration to the fixed span of playback time. Reading a unit of video data from video buffer316effectively de-queues the unit of video data from video buffer316. The sequence of video frames is then rendered by graphics interface326and transmitted to graphics device328to be displayed to a user.

An audio decoder318reads units of audio data from audio buffer314and output the units of audio data as a sequence of audio samples, generally synchronized in time with a sequence of decoded video frames. In one embodiment, the sequence of audio samples are transmitted to audio interface330, which converts the sequence of audio samples into an electrical audio signal. The electrical audio signal is then transmitted to a speaker of audio device332, which, in response, generates an acoustic output.

In situations where the bandwidth of distribution infrastructure110is limited and/or variable, playback application310downloads and buffers consecutive portions of video data and/or audio data from video encodings with different bit rates based on a variety of factors (e.g., scene complexity, audio complexity, network bandwidth, device capabilities, etc.). In some embodiments, video playback quality is prioritized over audio playback quality. Audio playback and video playback quality are also balanced with each other, and in some embodiments audio playback quality is prioritized over video playback quality.

Graphics interface326is configured to generate frames of video data and transmit the frames of video data to graphics device328. In one embodiment, graphics interface326is included as part of an integrated circuit, along with processor122. Alternatively, graphics interface326is configured as a hardware accelerator that is distinct from (i.e., is not integrated within) a chipset that includes processor122.

Graphics interface326generally represents any type or form of device configured to forward images for display on graphics device328. For example, graphics device328is fabricated using liquid crystal display (LCD) technology, cathode-ray technology, and light-emitting diode (LED) display technology (either organic or inorganic). In some embodiments, graphics device328also includes a virtual reality display and/or an augmented reality display. Graphics device328includes any technically feasible means for generating an image for display. In other words, graphics device328generally represents any type or form of device capable of visually displaying information forwarded by graphics interface326.

As illustrated inFIG. 3, content player120also includes at least one input device336coupled to communication infrastructure302via input interface334. Input device336generally represents any type or form of computing device capable of providing input, either computer or human generated, to content player120. Examples of input device336include, without limitation, a keyboard, a pointing device, a speech recognition device, a touch screen, a wearable device (e.g., a glove, a watch, etc.), a controller, variations or combinations of one or more of the same, and/or any other type or form of electronic input mechanism.

Content player120also includes a storage device340coupled to communication infrastructure302via a storage interface338. Storage device340generally represents any type or form of storage device or medium capable of storing data and/or other computer-readable instructions. For example, storage device340may be a magnetic disk drive, a solid-state drive, an optical disk drive, a flash drive, or the like. Storage interface338generally represents any type or form of interface or device for transferring data between storage device340and other components of content player120.

Many other devices or subsystems are included in or connected to content player120. Conversely, one or more of the components and devices illustrated inFIG. 3need not be present to practice the embodiments described and/or illustrated herein. The devices and subsystems referenced above are also interconnected in different ways from that shown inFIG. 3. Content player120is also employed in any number of software, firmware, and/or hardware configurations. For example, one or more of the example embodiments disclosed herein are encoded as a computer program (also referred to as computer software, software applications, computer-readable instructions, or computer control logic) on a computer-readable medium. The term “computer-readable medium,” as used herein, refers to any form of device, carrier, or medium capable of storing or carrying computer-readable instructions. Examples of computer-readable media include, without limitation, transmission-type media, such as carrier waves, and non-transitory-type media, such as magnetic-storage media (e.g., hard disk drives, tape drives, etc.), optical-storage media (e.g., Compact Disks (CDs), Digital Video Disks (DVDs), and BLU-RAY disks), electronic-storage media (e.g., solid-state drives and flash media), and other digital storage systems.

A computer-readable medium containing a computer program is loaded into content player120. All or a portion of the computer program stored on the computer-readable medium is then stored in memory124and/or storage device340. When executed by processor122, a computer program loaded into memory124causes processor122to perform and/or be a means for performing the functions of one or more of the example embodiments described and/or illustrated herein. Additionally or alternatively, one or more of the example embodiments described and/or illustrated herein are implemented in firmware and/or hardware. For example, content player120is configured as an Application Specific Integrated Circuit (ASIC) adapted to implement one or more of the example embodiments disclosed herein.

FIG. 4illustrates a computing environment400that includes a computer system401. The computer system401is substantially any type of computing system including a local computing system or a distributed (e.g., cloud) computing system. The computer system401includes at least one processor402and at least some system memory403. The computer system401includes program modules for performing a variety of different functions. The program modules are hardware-based, software-based, or include a combination of hardware and software. Each program module uses computing hardware and/or software to perform specified functions, including those described herein below.

The computer system401also includes a communications module404that is configured to communicate with other computer systems. The communications module404includes any wired or wireless communication means that can receive and/or transmit data to or from other computer systems. These communication means include hardware interfaces including Ethernet adapters, WIFI adapters, hardware radios including, for example, a hardware-based receiver405, a hardware-based transmitter406, or a combined hardware-based transceiver capable of both receiving and transmitting data. The radios are cellular radios, Bluetooth radios, global positioning system (GPS) radios, or other types of radios. The communications module404is configured to interact with databases, mobile computing devices (such as mobile phones or tablets), embedded or other types of computing systems.

The computer system401also includes a determining module407. The determining module407is configured to determine when to adjust audio video quality in a multimedia stream. The determining module407is also configured to determine the amount by which to adjust the audio quality. For example, inFIG. 4, the determining module407monitors the multimedia stream413that is being streamed to the content player412. The multimedia stream413includes any type of audio data414, video data415, text, pictures, or other types of multimedia content. In some cases, the determining module407determines that audio quality is to be adjusted, either upward or downward. Adjusting the audio quality level409includes increasing or decreasing an audio bitrate, changing an audio encoding scheme, changing from two-channel to 5.1 channel or to 7.1 channel or to some other number of channels, or otherwise changing characteristics of the audio data414. The determining module407determines that the audio is to be adjusted based on a variety of factors including current network bandwidth between the computer system401and the content player412, current video quality level410, capabilities of the content player, or other factors.

Once the determining module407has determined that at least one of the stream properties408of the multimedia stream413is to be changed, the adjusting module411changes the stream properties408by applying stream adjustments417. These adjustments417change one or more characteristics associated with the audio quality level409. In some cases, the stream adjustments417are applied dynamically during the multimedia stream413. For example, if the network bandwidth between the computer system401and the content player412changes (e.g., if the content player is running on a mobile device that is moving in between cells), the determining module407monitors these changes and adjusts the audio quality level409and/or the video quality level410accordingly.

In some embodiments, the provider of the multimedia stream413or the persons viewing the multimedia stream (via the content player412) indicate that the video quality level410is to be prioritized above the audio quality level409. As such, if the network bandwidth drops between the computer system401and the content player412, the video data415in the multimedia stream413will be maintained at a higher level than the audio data414. Over time, the network bandwidth typically fluctuates up and down, allowing more or less data to be transferred. As the network bandwidth fluctuates, the audio quality level409will also fluctuate but will be held below a specific level. This level is determined, by the determining module407, to be a point at which maintaining a certain audio quality level409would interfere with maintaining a certain video quality level410. Thus, for instance, if the video quality level410were to be maintained at a minimum level of 3 Mbps, and if maintaining an audio quality level of 768 Kbps would bring the video quality level410below 3 Mbps, then the audio quality level would be dropped to maintain the minimum video quality level. These and other concepts will be explained in greater detail below with regard to method500ofFIG. 5and with regard toFIGS. 6-11.

FIG. 5is a flow diagram of an exemplary computer-implemented method500for adaptively streaming multimedia content. The steps shown inFIG. 5are be performed by any suitable computer-executable code and/or computing system, including the system illustrated inFIG. 4. In one example, each of the steps shown inFIG. 5represents an algorithm whose structure includes and/or is represented by multiple sub-steps, examples of which will be provided in greater detail below.

As illustrated inFIG. 5, at step510, one or more of the systems described herein determines that audio quality is to be adjusted for a multimedia streaming connection over which audio data and video data are being streamed to a content player. For example, in some cases, the determining module407determines that the audio quality level409is to be adjusted for multimedia stream413. The multimedia stream413is streamed from a provider (e.g., computer system401) to a content player412. As noted above, the content player412is a software program that is instantiated on any of a number of different types of electronic devices. Within the multimedia stream413, the audio data414is streamed at a specified audio quality level409and the video data415is streamed at a specified video quality level410. The quality level of the audio or video data determines the fidelity at which the underlying multimedia content is reproduced by the content player. If a high-quality audio stream is provided, the content player412will play the audio at a higher bitrate or in a higher-quality encoding. Similarly, if a lower-quality audio stream is provided, the content player412will play the audio at a lower bitrate or in a lower-bitrate encoding.

Method500ofFIG. 5further includes determining, at step520, that a specified minimum video quality level is to be maintained while adjusting the audio quality level. Traditional content players and content streaming systems do not set a minimum level for video and then adjust the audio quality within those confines. Thus, in contrast to traditional systems that simply downgrade or upgrade video based on available bandwidth, the embodiments described herein determine that specified minimum video quality level410is to be maintained while adjusting the audio quality level409. Accordingly, a minimum video quality level410is established and the audio quality level409is adjusted upward as bandwidth is available, but not beyond the point where the higher quality audio would take sufficient bandwidth away from the video data as to pull the video quality level410below the specified minimum level. Method500ofFIG. 5also includes, at step530, dynamically adjusting the audio quality level of the multimedia streaming connection while maintaining the video quality level of the multimedia streaming connection at at least the specified minimum video quality level. Examples of dynamic audio quality adjustments are shown inFIG. 6.

FIG. 6shows a chart600with an initial video quality level601and an initial audio quality level603. The chart600also shows an established minimum video quality level (Vmin)602and established minimum audio quality level (Amin)604. It will be understood here that the actual, real-life quality levels are changeable and could be different in each situation. For instance, in some cases, the video quality level601is different for a television than it is for a cell phone. Similarly, the audio quality level is different for a streaming set-top box than it is for a laptop or tablet computer system. Thus, the actual numbers used (e.g., the bitrate or encoding rate) are less important than the ratios between audio quality level and video quality level.

For example, at time T1inFIG. 6, the video quality level601transitions from an initial value to a lower value (perhaps due to network interference, for example). Because the video quality level601has not reached the minimum video quality level (Vmin), the audio quality level603is not reduced. Also, in some cases, the audio level is increased at this point since the video quality level601is not at Vmin. At time T2, however, the network experiences another degradation in quality and the video quality level601drops to Vmin602. At this point, the adjusting module (e.g.,411ofFIG. 1) dynamically adjusts the audio quality level603downward by a specified amount. In some cases, the amount includes a single increment (e.g., from 384 Kbps to 256 Kbps) while in other cases, the amount includes multiple increments (e.g., from 384 Kbps to 128 Kbps). In some embodiments, the determining module407ofFIG. 4determines how much additional bandwidth is needed to bring the video quality level601up to or substantially above the minimum level602. This amount of bandwidth then determines the amount by which the audio quality level is reduced. The additional bandwidth that is now available as a result of dropping the audio quality level is used to provide an increased video quality level.

At time T3in chart600, the network bandwidth has improved and the video quality level601increases to the initial value, well above Vmin. Accordingly, the adjusting module411ofFIG. 4dynamically adjusts the audio quality level603upwards to a near maximum level (e.g., 512 Kbps). At time T4, because the video quality level is holding steady, the adjusting module411again dynamically increases the audio quality level603. Thus, as can be seen, over time, the audio quality level603is continually adjusted to provide the highest possible audio quality level for the content player412. If bandwidth drops and video quality begins to degrade, the audio quality is dropped to the point that video quality is maintained at at least Vmin. In this manner, the embodiments herein provide the highest quality audio possible without degrading the video quality beyond a specified point.

In other embodiments, the determination to increase or decrease the audio quality level603is based solely on available bandwidth. The system continually determines how much bandwidth is available for audio and/or video and adjusts the audio quality level accordingly. Thus, at time T2, for example, the system may determine that available bandwidth has dropped, or that the audio buffer has dropped below a specified amount of buffered data. The system may then later determine, at time T3and again at time T4, that the available bandwidth has increased. As such, the system increases the audio quality level to a higher quality level at T3and to the highest quality level at T4.

As noted above, a content player includes a general-purpose processor (e.g., a central processing unit (CPU)) or special-purpose processor (e.g., an ASIC or FPGA) that is configured to decode an audio or video data stream. These processors receive the audio and video data from a network adapter and process the data to generate audio and/or video signals that are then sent to speakers and/or a display, respectively. Across different playback devices, however, these general-purpose and special-purpose processors have varying abilities to decode the audio and video data. More specifically, some processors are better than others at handling certain types of encoding or handling certain data rates. Indeed, each of potentially thousands of different types of phones, tablets, televisions, audio receivers, surround sound systems, wearable devices, and other playback devices have slightly or significantly different capabilities and limitations. Some of these devices are not capable of dealing with changes to audio bit rates or do not support certain audio encodings.

For example, as shown inFIG. 7, a multimedia provider701provides multimedia content710to different electronic devices703and707. Each of the electronic devices703and707has different A/V hardware (704and708, respectively). Each electronic device703/707reports its device capabilities702/706to the multimedia provider701. The multimedia provider then creates customized data streams705/709that are specific to the capabilities of each device. Thus, in one embodiment for example, the determining module407ofFIG. 4determines that a content player (e.g.,412) is operating on a specified electronic device. The determining module407then identifies audio and/or video hardware capabilities of the specified electronic device (e.g., based on self-reported or queried device capability data702/706), and the adjusting module411and dynamically adjusts the audio quality level of the multimedia streaming connection according to the audio or video capabilities of the specified electronic device. Thus, if the electronic device can only handle low definition video, low-definition video will be transmitted in the data stream. On the other hand, if the electronic device can handle high-definition video, the multimedia provider701will provide high-definition video.

FIG. 8shows graph800with a distortion curve that represents estimated perceived audio quality at certain bitrates for Dolby Digital Plus (DD+)5.1. These types of distortion curves are used to identify bitrate switching thresholds. Alternatively, these distortion curves are used to identify encoding technologies to use at certain bitrates, and/or as a consideration in one or more other aspects of designing or implementing an adaptive bitrate audio system.

The adaptive bitrate audio systems described herein use various algorithms and procedures to determine when to upswitch to a higher bitrate or when to downswitch to a lower bitrate. For example, as noted inFIG. 7, when an electronic device (e.g.,703) connects to a multimedia provider (e.g.,701), the device presents its audio capabilities to the multimedia provider. The provider determines, based on the device capabilities, throughput history detected during prior connection to the device, and/or any other suitable factor, which audio stream it will signal and provide to the electronic device.

In one example, if throughput history is available for an electronic device, for the initial audio stream the server selects a bitrate less that is less than a particular percentage (e.g., 15%) of throughput history. In this example, if the throughput history indicates a prior average bitrate of 1 Mbps, the server selects a bitrate around or less than 150 kbps. Similarly, if the throughput history indicates 5 Mbps, the server selects a bitrate around or less than 750 kbps. In some embodiments, the server rounds down to the closest bitrate that is available on the server and that is compatible with the device. In the example with 1 Mbps throughput history, the server selects a bitrate of 96 kbps, and in the example with the throughput history of 5 Mbps, the server selects a bitrate of 640 kbps.

In some cases, a multimedia provider or distribution server uses factors other than throughput history to identify a bitrate for an initial stream. For example, if throughput history isn't available for a device, the server then selects the lowest available bitrate stream compatible with that device. In another example, a device indicates a preferred stream (e.g., via device settings, user preferences, etc.) to the server, and the server selects an audio stream based on this preference.

FIG. 9shows an example of audio bitrates and encodings that are used for particular throughput history ranges. In the graph900, a throughput history of around 427 kbps to 640 kbps triggers a 64 kbps encoding (e.g., using AAC), a throughput history of around 640 kbps to 1280 kbps triggers a 96 kbps encoding (e.g., using AAC 2.0), a throughput history of around 1280 kbps to 2560 kbps triggers a 192 kbps audio encoding (e.g., using either AAC 5.1 or DD 5.1), and a throughput history of 2560 kbps or higher triggers an audio bitrate of 384 kbps (e.g., using Dolby Atmos). In some embodiments, an audio stream is limited to switching between different bitrates of a particular encoding scheme. In one example, an audio stream is switchable from AAC 2.0 at 96 kbps to AAC 2.0 at 192 kbps but is not switchable from AAC 2.0 at 96 kbps to DD 5.1 or Atmos, regardless of bitrate. Alternatively, an audio stream is switchable between different encoding technologies (e.g., from AAC 2.0 to DD 5.1) if a distribution server and/or a playback device support this type of switching.

FIG. 10illustrates a graphical representation1000of another adaptive audio bitrate scheme. As shown inFIG. 10, AAC 2.0 is switchable between 64 kbps and 96 kbps, AAC 5.1 has a single bitrate at 192 kbps, DD 5.1 is switchable between five bitrates (e.g., 192 kbps, 256 kbps, 384 kbps, 448 kbps, and 640 kbps), and Atmos is switchable between 384 kbps and 448 kbps. In other examples, certain high bitrate encoding technologies (e.g., Atmos) are not switchable between different bitrates while other lower-bitrate encoding technologies (e.g., DD 5.1, AAC 5.1, AAC 2.0, etc.) are switchable.

Distribution systems switch between different bitrates in a variety of ways. In one example, a distribution system only upswitches a stream one step at a time (e.g., a content server upswitches from DD 5.1 192 kbps to 256 kbps but does not skip a step by switching from 192 kbps to 384 kbps). In some situations, single step upswitching helps avoid rebuffering by not switching to a bitrate that cannot be handled or maintained by the device. While single-step upswitching is advantageous in certain scenarios, a distribution system also skips one or more steps when upswitching.

Distribution systems consider various factors when deciding whether to upswitch an audio stream. In some examples, a distribution system only upswitches if predicted or detected audio throughput is greater than or equal to a threshold associated with the next audio bitrate in an upswitch ladder. A distribution system also considers the size of the audio buffer and/or any other suitable factor when determining whether to upswitch an audio stream. In some cases, for example, a distribution server require that a playback device have an audio buffer of at least a particular size for that device to be allowed to upswitch to a particular bitrate.

Like the upswitching scenarios where audio stream quality is upswitched to a higher quality, downswitching is triggered a single step at a time or multiple steps at a time. In at least one example, a distribution server only allows for single-step upswitching while providing multi-step downswitching. The opposite is also possible, where the distribution server only allows for single-step downswitching while providing multi-step upswitching. In some cases, downswitching is triggered by the prediction or detection of audio throughput being lower than a throughput associated with a current bitrate. In one example, a distribution server prevents a stream that has been upswitched or downswitched from being changed again for a predetermined period of time (e.g., a period of time associated with a buffer size of a playback device).

In some cases, a distribution server uses upswitch and/or downswitch factors in determining whether to change the bitrate of an audio stream. The upswitch and downswitch factors may be the same or different. For example, in some cases, the distribution server upswitches an audio stream to the next bitrate if predicted audio throughput is greater than or equal to the product of an upswitch factor and the next audio bitrate. Conversely, in other cases, the distribution server downswitches an audio stream if predicted audio throughput is less than the product of a down-switch factor and the current audio bitrate.

Some systems use an upswitch factor that is higher than a downswitch factor and also set a minimum buffer time required for upswitching and a minimum lock period after downswitching. In one example, a distribution server sets the upswitch factor to 2.0, the downswitch factor to 0.8, the minimum buffer time to 16 seconds, and the post-downswitch lock period to 32 seconds. In this example, if a current audio bitrate is 256 kbps, the playback device would need to have at least 16 s of audio buffered at the current bitrate and at least 2.0*384 kbps (i.e., 768 kbps) of predicted audio throughput before upswitching to 384 kbps. Continuing with this example, the distribution system downswitches from 256 kbps to 196 kbps if predicted audio throughput is less than 0.8*256 kbps (i.e., 204 kbps). In some cases, after downswitching, the distribution system requires the playback device to buffer at least 32 seconds of audio before allowing the playback device to upswitch to a higher bitrate.

As suggested in the examples above, audio buffer size play a significant role in a device's ability to upswitch to higher bitrates.FIG. 11illustrates the relationship between buffer size and throughput by depicting an upswitch/downswitch ladder for various audio rates. As shown in chart1100ofFIG. 11, the larger the buffer size, the less throughput is needed before upswitching to a higher bitrate audio stream. Conversely, the smaller the buffer size, the more throughput is needed before switching to higher quality audio.

In some cases, the data bit rate for the audio stream changes over time and, at least in some cases, changes dramatically. For example, the data bit rate changes when the user is moving in and out of cell phone coverage when in a car. To compensate for such changes in available bandwidth, a distribution system (e.g.,401ofFIG. 4) implements a series of network tests to determine the current available bandwidth between the distribution system and the user's playback device. The distribution system then uses this determination to choose an appropriate bit rate for one or more of the content streams.

As noted above, when multimedia content is streamed in conventional systems, it is typically encoded at a specific bit rate. While some video streaming services provide variable bit-rate video content, audio is typically still provided at a fixed rate. In the embodiments described herein, however, the distribution system provides an audio stream and/or other media streams at a variable rate that increases at certain times and decreases at other times in response to available bandwidth or other factors.

When varying the bit rate for an audio stream, the distribution system takes into consideration the video bit rate. At least in some embodiments, providing high-quality video is the top priority, and providing high-quality audio is a secondary consideration. In such cases, the distribution system provides a video signal that is optimal for the network conditions and then uses any remaining bandwidth to transmit an audio signal that is as high quality as possible.

For instance, when distribution systems deliver content to playback devices, the distribution systems determine how much bandwidth is currently available and further determine the playback device's ability to handle changes in bit rate. The embodiments described herein provide an optimal audiovisual experience for end users and, as such, prioritize transmission of video content while adjusting audio content within the available bandwidth. As noted above, if a given connection has a particular amount of available bandwidth, the majority of that bandwidth is taken by video data and a small portion is left over for audio data. In some cases, the systems described herein incrementally increase audio quality without impacting the quality of the video signal (as described in conjunction withFIG. 6). In such cases, the disclosed systems automatically increase the bit rate for the audio stream, thereby increasing the quality of the audio. If the user's connection slows and the available bandwidth is reduced, the bit rate for the audio stream is dynamically reduced to ensure that video quality is not impacted or is only minimally impacted by the reduced bandwidth.

When making a change in bit rate (either upwards or downwards), the distribution system uses various processes to determine which type of device is consuming the content. In one example, the distribution system obtains information about the capabilities of a content player when the content player first connected to a cloud server of the distribution system. In such cases, the distribution system caches the information about the content player for later use in determining whether to adjust an audio bitrate. In another example, the distribution system, when determining whether to adjust an audio bit rate, sends a query to a device to determine capabilities of the device. In yet another example, a user has an account with the distribution system and the user's device information is stored in association with that user. The device information (e.g.,702) is then used when streaming audio-video content to the playback device. Information about the capabilities of a device includes direct information about a device's capabilities (e.g., bitrates supported by the device, encoding formats supported by the device, etc.) or indirect information that is used to look up a device's capabilities (e.g., the brand of the device, the model number of the device, the operating system used on the device, etc.).

If the user is in a location that has a wired connection or a high capacity wireless connection, the amount by which the bit rate is adjusted is almost solely dependent on the capabilities of the device. For instance, in a hypothetical scenario in which a playback device has a strong network connection, the distribution system would be able to transfer data at substantially any rate and encode the data at any bit rate. The playback device, however in some cases, is a limited-capability phone, such as a feature phone that has reduced functionality relative to other smartphones. Such feature phones have relatively slow central processors and have limited capabilities for decoding audio and video content. As such, even if the network connection allows a higher bit rate, a playback device's hardware constraints still cause the distribution system to limit the audio signal's bit rate. Accordingly, in such cases, the distribution system places limits on certain devices or types of devices, for example, by establishing maximum allowable bit rates for those devices. Over time and after creating audio-video content sessions with many different types of devices, the distribution system thus generates a collection of settings and policies for different devices or types of devices, indicating each platform's capabilities and limitations.

In some cases, content players have a specified cache area (e.g., content buffer312of content player120) that buffers audio and video content separately as the content is streamed. In such devices, a video cache is larger than an audio cache, as video reproduction involves larger data streams. Distribution systems aim to fill these video and audio caches with, for example, between 30 seconds and 2 minutes of buffered content. And, if a data rate is chosen for the audio data that is too high for a given device's audio buffer, that audio buffer will not be able to cache enough audio content to avoid rebuffering.

For example, if the distribution system is streaming audio-video content to a device at 640 kbps, and the device only has a 2 MB audio cache, the cache is only able to hold a few seconds of buffered data. Whereas if the audio data is being streamed at 128 kbps, a 2 MB cache is able to store five times more buffered data. Accordingly, the distribution system also takes into consideration the size of the playback device's audio cache when initially selecting and later adjusting an audio stream's bit rate. Still further, in some cases, each playback device is configured to run certain audio-video playback software applications. Some software applications are more efficient at decoding audio and/or video data and are thus able to process higher bit rates on less powerful hardware. Other software applications are less efficient. Accordingly, the distribution system also considers the playback device's installed software applications when selecting and/or adjusting an audio stream's bit rate.

In this manner, both hardware and software constraints are accounted for when selecting and adjusting an audio stream bit rate. Unlike the above-described scenario, however, where bandwidth is not a concern, in many real-world scenarios bandwidth is a factor, and is often a significant factor, when determining the bit rate for an audio stream. As such, the distribution system notes and considers the relevant device-related constraints, bandwidth-related constraints, and/or other considerations when determining an optimal audio stream bit rate. Once the distribution system has begun providing the multimedia stream, the distribution system determines, according to device and/or bandwidth constraints, the highest available audio stream bit rate for transferring the audio stream. The distribution system then adjusts this bit rate over time to ensure that, even as the bandwidth changes, the bandwidth that is available is properly allocated, prioritizing video while optimizing audio within the remaining capacity.

Thus, the distribution system determines how to allocate bandwidth based not only on the device constraints, but also the continually changing available bandwidth. As the bandwidth changes in the connection between the playback device and the distribution system, the audio signal is upgraded or downgraded dynamically, according to these constraints. In some cases, the bit rate for a given audio stream also depends on the content of the audio. Indeed, some audio content is more complex than other audio content. For instance, in a 5.1 surround sound audio data stream, there are moments when some of the six speakers do not have any signals directed to them. In such cases, the distribution system omits transmitting audio content for those speakers. At other times, all six speakers will have audio content directed to them. Accordingly, the distribution system increases the bit rate of the audio signal for such moments in a song or movie and decreases the bit rate of the audio signal at other times in the song or movie. In some embodiments, these changes to the bit rate based on audio content occur regardless of bandwidth or device constraints or are performed within the established bandwidth and device constraints.

Another factor distribution systems consider for setting audio and/or video bitrates is the complexity of audio or video within a scene. For instance, if a user is watching a video stream that depicts two people talking, some portions of the audio track are be filled with silence. As such, data corresponding to those periods of silence does not need to be transmitted to a content player or only needs to be transmitted at a relatively low bit rate. Accordingly, the distribution system reduces the audio bit rate for those scenes that are less complex. On the other hand, if the user is watching an action scene with an up-tempo score, the audio data is relatively complex. As such, the distribution system increases the variable bit rate based on the complexity of the audio content.

When using video or audio complexity as a factor in determining playback rates, a content player receives a complexity map associated with the content (e.g., video, audio, or both) to be played. The complexity map specifies the complexity level of different scenes or sections of the video and/or audio streams. When selecting the next portion of video data or audio data for download, the content player determines the complexity level of the scene based on the scene complexity map.

Based on the complexity level of the scene and one or more performance factors, the content player then determines the particular video or audio encoding from which to download the portion of the video or audio data. For example, in a scenario where the bandwidth is limited and a scene has low complexity, the content player downloads the portion of video data and/or audio data associated with the scenes from low bit-rate encodings. In this manner, bandwidth is conserved and used to buffer subsequent, and potentially more complex, scenes from higher bit-rate encodings. Other factors that influence the specific encoding from which to download the portion of audio or video data include complexity levels of subsequent scenes, the behavior of the end user consuming the content, the type of output device rendering the content (e.g., high-definition, standard-definition, etc.), and/or the available lead time. These factors combined with the bandwidth limitations of a network connection and/or capabilities of a content player are used to select audio or video encodings from which to download each portion of a media title.

In some cases, the audio content provided by the content source includes metadata indicating which portions of the audio signal are more or less musically complex or involve signals for more or fewer of the surround sound speakers. This metadata indicates timeframes, for example, when a higher bit rate should be used. The metadata states, for example, that a higher bit rate should be used during the data transfer for certain sections of the content. The content server then encodes the audio data at a higher bit rate, constrained by current bandwidth and playback device limitations. As such, the distribution system, knowing which device (or device type) is consuming the content, encodes the audio content based on metadata indications provided with the content. In some examples, the audio encoding is based on currently available bandwidth in the device's connection and/or is based on hardware or software constraints associated with that device.

In this manner, each portion of the audio stream is fully and dynamically customized within any one or more of the above-described constraints. For example, even if the metadata says to increase the audio bit rate (e.g., due to an increase in musical complexity), the distribution system resolves not to (e.g., based on current bandwidth limitations or based on the knowledge that the device's hardware cannot handle the higher bit rate). In another example, the distribution system determines that a relatively small amount of bandwidth is currently available and that the playback device can handle a slightly higher bit rate. In such cases, the distribution system dynamically increases the audio signal bit rate in response to the metadata indication. Other indications or signals trigger a reduction in bit rate at a later point in time.

In some cases, a distribution system considers initial startup time (or “startup delay”) when selecting an initial audio stream bit rate. For example, when a user selects a given video or song, the user typically expects the video or song to start as soon as possible. Anything longer than a few seconds greatly detracts from the user's experience or results in the user seeking entertainment elsewhere. Accordingly, the distribution system takes extra precautions to ensure that the audio-video content's initial startup time is as low as possible. In this regard, the distribution system conducts a throughput estimation (prior to or while providing the audio-video content) that indicates the current or expected data throughput to the user's playback device. This throughput estimation is based on historical data and/or an initial amount of data traffic transferred between the distribution system and the playback device. In some cases, the initial communication provides an indication of currently available bandwidth. Additionally or alternatively, the distribution system has established network sessions with the playback device before. The distribution system stores metadata associated with that user's session, and the metadata includes the device's IP address, data transfer rate, device type, operating system, web browser type, playback application used, etc. Any or all of this information is used when choosing an initial data bit rate to use when performing the initial startup.

As noted, the throughput estimation indicates an amount of bandwidth that is currently available between the distribution system and the playback device. In some cases, this throughput estimation is modified or calculated based on previous connection session data. Once the current throughput has been estimated, the distribution system then streams the audio-video data at a rate that is less than the amount indicated in the throughput estimation. This slower bit rate is referred to herein as a discount or margin curve, indicating that a lower bit rate will be used at startup than the maximum bit rate. This discount or margin curve refers to a curve in a graph that illustrates how a lower-than-maximum bit rate is used at startup and, over time, approaches the maximum bit rate for the current conditions (e.g., device capabilities, bandwidth, etc.).

Accordingly, when initially starting an audio-video stream, the distribution system streams the data at a bit rate that is, for example, 75% of the maximum available. Then, over time, the distribution system increments that upwards until the bit rate is at or close to 100% of the maximum available at that moment. In some cases, the margin curve is different for audio data than would be used with video data. For example, because audio buffers have smaller caches, and because video quality is prioritized over audio quality (at least in some cases), video margin curves skew higher such that the initial bit rate for video is at 85-90% of the maximum available bit rate, thereby providing higher quality. In devices that have a larger audio cache, the margin curve also skews higher since more data is buffered. Conversely, in playback devices that have smaller data caches, the margin curve skews smaller, indicating that a bit rate of 60-70% of the maximum bit rate should be used since only a small amount of data is buffered on such devices.

In some cases, the distribution system streams data based on these margin curves or opts to stream data in a different manner. For instance, in some examples, the distribution system disregards or even omits the throughput estimation and simply begins streaming data at a lower rate. This lower data rate is specific to certain devices or specific to certain computer networks and, as such, applies to all devices on that network. The lower data rate is provided for a specified amount of time and then, if sufficient bandwidth is available, the distribution system increases the bit rate of the streamed data. Accordingly, the distribution system has a large amount of control over how the data is initially streamed to the playback device as well as over how the bit rate is changed throughout the extent of the data stream.

In some embodiments, the distribution system packages the audio data stream in a manner that indicates to the playback device when it can switch to data encoded at a different bit rate. For example, in some cases, the hardware and/or software running on the user's playback device is expecting audio data packets encoded at a specific bit rate. An indicator is incorporated within the audio data stream as a hook to notify the playback device when an upswitch or downswitch is permitted to occur. The distribution system uses these indicators to enable seamless switching to higher or lower bit rates for an audio stream. After switching to a new bit rate (either higher or lower than the previous bit rate), each transmitted data block of the new audio stream has more or less data and consumes different amounts of buffer space within the data block. The indicators identify the new bit rate and/or the new amount of data that will be included in each transmitted data block. The playback device then looks for the different data blocks and continues providing the audio stream to the user, switching between streams with different bit rates in a seamless and fluid manner. In some embodiments, a manual implementation is provided in which a user or software routine triggers bit rate changes manually. For example, after a user requests a bit-rate change on a content player, the content player sends a notification to the content provider requesting the new bit rate. The content server then transmits future data blocks encoded with the manually selected bit rate.

Accordingly, whether using a manual selection of bit rates or an automatic selection of bit rates based on available bandwidth and/or other factors, the embodiments described herein provide improved audio quality of experience (QoE) for a user without detracting from the video QoE. In some embodiments, the playback device is streaming multiple audio, video, or other data streams at the same time. In one example, a user is playing a video game and is streaming music in addition to streaming the video and audio content of the game. Or, in another example, the playback device is streaming a movie or video game as well as a video or audio chat session in which users are discussing the movie or video game. Other data streams include haptic content for wearable devices, artificial reality content for augmented reality glasses or virtual reality headsets, and/or various other types of content. In such cases, the distribution system adjusts bit rates of each of these streams in relation to the other data streams to increase the QoE of an end user.

For instance, if a playback device is receiving three data streams, the available receiving bandwidth at that device is divided among the three data streams. In such cases, some content (e.g., audio or video) is prioritized over other content (e.g., haptics data). Furthermore, users provide preferences regarding the various types of content, indicating how and when data stream bit rates are to be adjusted. Accordingly, even in scenarios where multiple different content providers are streaming content to a single playback device, each of these content providers follows policies and user preferences indicating when their data content streams are to be adjusted in line with the network bandwidth that is currently available.

In some embodiments, certain types of devices, or certain brands or models or hardware versions, are whitelisted or blacklisted as devices that are capable or incapable of handling these adjustments to bit rates. Indeed, as mentioned above, some devices lack the processing power, network capabilities, or the cache size to handle changes in bit rate. In some embodiments, content providers (or perhaps third-party services) test certain devices or device families to determine which devices can handle manual or automatic audio stream adjustments. During testing, some devices repeatedly attempt to rebuffer, freeze during playback, or produce audio artifacts that are unappealing and detract from the end-user experience. The distribution system blacklists such devices so that audio stream adjustments do not occur when streaming audio-video content to those devices. Other devices that are tested and shown to be able to handle audio stream adjustments are whitelisted and audio streams to those devices are adjusted according to bandwidth and perhaps other device-related constraints.

In some cases, playback devices are whitelisted or blacklisted based on user feedback or user behavior. For example, if multiple users are viewing a video on a certain type of mobile device such as a phone, and a sufficient number of those users quit viewing the video at or near points at which the audio was automatically adjusted, the distribution system infers that the audio adjustments had a negative effect on the user's experience. Conversely, if multiple users are viewing a video on a certain type of playback device and a sufficiently high number of those users watch the video past the points at which the audio was automatically adjusted, the distribution system infers that the audio adjustments did not have an adverse effect on the user's video watching experience. Still further, in some cases, the user provides explicit feedback in the form of an email or a survey or an app rating, indicating that the audio sounded grainy and muffled, or sounded detailed and accurate. The distribution system uses such feedback as a factor when determining whether to blacklist or whitelist a given device.

When switching to audio streams with higher or lower bit rates, substantially any bit rate may be used, including from 32 to 64 to 96 to 128 kbps on the lower end to 256, 448 or 640 kbps on the higher end. Of course, bit rates below or above the listed bit rates are also used. Lower bit rates are used more with limited functionality mobile devices such as flip phones or wearable devices, while higher bit rates are used with televisions and home theaters. In some embodiments, the distribution system transmits high quality Dolby Digital 5.1 or 7.1 streams, Dolby Atmos streams, lossless audio streams that use, for example, the free lossless audio codec (FLAC), the waveform audio file format (WAV), or other high-end audio streams. These high-bit-rate audio streams are selected based on the bandwidth and device constraints identified above, as well as content characteristics as indicated by metadata associated with the content. As such, the high-bit-rate audio streams are provided alongside high-quality video streams without impacting the video streams.

In some cases, distribution systems provide high-end audio or low-end audio as part of different tiered service plans. For example, a content provider markets high-bit-rate audio streams as a selling point to users that have home theaters or high-quality speakers. Such users are willing to pay more to have higher-quality audio streams. Conversely, users that only watch content on their mobile devices are content with a plan that provides lower-quality audio that consumes less data. When such users are viewing content on their mobile device, they receive an audio stream at a quality level that is acceptable to them while avoiding the high data usage that would come with a higher-tiered plan. Accordingly, in each case, a content provider presents plans that are suited to each user's needs. Users that care about high-definition sound choose a high-bit-rate plan, and users who are content with lower-quality sound select a lower bit-rate plan.

In this manner, a distribution system uses the systems herein to provide improved audio and/or multimedia experiences to its users. For example, the distribution system prioritizes a video stream and select a video encoding bit rate that reflects this priority. Then, with the remaining bandwidth, the distribution system adjusts the audio bit rate based on a variety of different factors, including available bandwidth and device capabilities. The distribution system changes the audio bit rate dynamically throughout a user's audio-video session, from the initial playback to the closing credits. Furthermore, devices that do not support such dynamic adjustments are blacklisted to ensure that each device's playback experience is satisfactory for that device. These and other embodiments are implemented together or separately to provide the features and advantages discussed herein.

EXAMPLE EMBODIMENTS

1. A computer-implemented method for adaptively streaming multimedia content, the method comprising: determining that audio quality is to be adjusted for a multimedia streaming connection over which audio data and video data are being streamed to a content player, the audio data being streamed at a specified audio quality level and the video data being streamed at a specified video quality level; determining that a specified minimum video quality level is to be maintained while adjusting the audio quality level; and dynamically adjusting the audio quality level of the multimedia streaming connection while maintaining the video quality level of the multimedia streaming connection at at least the specified minimum video quality level.

2. The computer-implemented method of claim1, wherein dynamically adjusting the audio quality level comprises increasing the audio quality level.

3. The computer-implemented method of claim2, wherein the audio quality level is automatically increased to one or more subsequent higher quality levels until the video quality level reaches a specified quality level that is higher quality than the specified minimum video quality level.

4. The computer-implemented method of claim1, wherein the audio quality level is adjusted according to a specified bitrate ladder.

5. The computer-implemented method of claim1, wherein the audio quality level is dynamically adjusted according to one or more user preferences, the user preferences indicating whether audio or video is to be prioritized in the multimedia streaming connection.

6. The computer-implemented method of claim1, further comprising: determining that the content player is operating on a specified electronic device; identifying one or more audio or video hardware capabilities of the specified electronic device; and dynamically adjusting the audio quality level of the multimedia streaming connection according to the audio or video capabilities of the specified electronic device.

7. The computer-implemented method of claim6, wherein the audio quality level is dynamically adjusted for a plurality of different types of electronic devices.

8. The computer-implemented method of claim6, wherein an audio data rate at which the audio data is transmitted over the multimedia streaming connection is varied based on a cache size associated with the specified electronic device.

9. The computer-implemented method of claim1, wherein dynamically adjusting the audio quality level comprises decreasing the audio quality level.

10. The computer-implemented method of claim9, wherein the audio quality level is dynamically decreased upon determining that network bandwidth for the multimedia streaming connection has dropped below a specified amount.

11. The computer-implemented method of claim9, wherein the video data corresponds to a movie or television show and wherein the audio quality level is dynamically decreased upon determining that an audio track associated with the movie or television show is substantially silent for at least a minimum specified period of time.

13. The system of claim12, wherein the video quality level is prioritized over the audio quality level in the multimedia streaming connection, such that the audio quality level is dynamically reduced to maintain a specified minimum video quality level.

14. The system of claim12, wherein a bit rate associated with the audio data in the multimedia streaming connection is varied dynamically based on underlying content associated with the audio data.

15. The system of claim12, further comprising, prior to streaming data through the multimedia streaming connection, determining a startup delay that would be incurred if a higher audio bitrate were to be used to stream the audio data.

16. The system of claim12, wherein the audio and video data are streamed to the content player according to one or more margin curves.

17. The system of claim12, wherein the audio quality level is dynamically adjusted for a plurality of audio data streams that are part of the multimedia streaming connection.

18. The system of claim12, further comprising: analyzing one or more portions of prior transmission data associated with audio and video data transferred during the multimedia streaming connection; predicting a future amount of audio and video data that will be transferred using the multimedia streaming connection; and dynamically adjusting the audio quality level based on the predicted future amount of audio and video data that is to be transferred using the multimedia streaming connection.

19. The system of claim12, further comprising locking the audio quality level at a specified level for at least a minimum amount of time after the dynamic adjustment.

20. A non-transitory computer-readable medium comprising one or more computer-executable instructions that, when executed by at least one processor of a computing device, cause the computing device to: determine that audio quality is to be adjusted for a multimedia streaming connection over which audio data and video data are being streamed to a content player, the audio data being streamed at a specified audio quality level and the video data being streamed at a specified video quality level; determine that a specified minimum video quality level is to be maintained while adjusting the audio quality level; and dynamically adjust the audio quality level of the multimedia streaming connection while maintaining the video quality level of the multimedia streaming connection at at least the specified minimum video quality level.

In some examples, the term “memory device” generally refers to any type or form of volatile or non-volatile storage device or medium capable of storing data and/or computer-readable instructions. In one example, a memory device stores, loads, and/or maintains one or more of the modules described herein. Examples of memory devices include, without limitation, Random Access Memory (RAM), Read Only Memory (ROM), flash memory, Hard Disk Drives (HDDs), Solid-State Drives (SSDs), optical disk drives, caches, variations or combinations of one or more of the same, or any other suitable storage memory.

In addition, one or more of the modules described herein transform data, physical devices, and/or representations of physical devices from one form to another. For example, one or more of the modules recited herein receives data to be transformed, transform the data, output a result of the transformation to monitor video quality, and use the result of the transformation to adjust audio quality while maintaining video quality. Additionally or alternatively, one or more of the modules recited herein transforms a processor, volatile memory, non-volatile memory, and/or any other portion of a physical computing device from one form to another by executing on the computing device, storing data on the computing device, and/or otherwise interacting with the computing device.