video recording in the cloud: use cases and...

Video Recording in the Cloud: Use Cases and Implementation

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The possibility of recording a live television channel is an application that has been available for end-users for many years, starting with videotapes in the 1970s. Since then, it has become a legitimate requirement, despite the type of delivery, to be able to record a program or a portion of a program for later viewing.

The traditional approach, which consists of allowing end-users to create their own private copy of content on local devices, has long been the only available method. Rights owners have accepted this feature, and it is strictly regulated by law to ensure that the content captured and copied is for private usage only. In most countries, taxes have been applied to recording and storage devices to create a compensating revenue stream for rights owners.

This balance is now being impacted by IP networks’ capabilities of storing content and streaming it on-demand to each end-user, allowing “cloud PVR” applications. Instead of storing the recorded content on a local drive, the content in this scenario is captured in the heart of the network and streamed as “video-on-demand” content, with all the trick mode functions (e.g., pause, fast rewind, fast forward) available. Additional applications such as start-over (i.e., get back at the beginning of a program), catch-up TV (i.e., watch a past program), or time-shifting (i.e., move back and forth in the live stream) can also be implemented the same way.

Based on the techniques used, this new approach may require regulatory changes to deliver the best service to end-users at the best cost.

This document describes the various use cases related to cloud PVR, in both managed (e.g., IPTV and cable TV) and unmanaged (e.g., OTT) network contexts, reviews its benefits, and explores different implementations.

Introduction


Cloud PVR use cases Within the cloud PVR approach, there are various applications.

Cloud Time-Shifting

Also known as Network time-shifting, pause TV, time-shift TV, delay TV

Use case: Press the pause button to pause live content, then the

play button to start playing it again from the pause position.

Use the fast rewind and fast forward buttons to browse the stream between a limit in the past and real time.

With the press of a button, one can instantaneously get back to real time.

Usage constraints: The service is usually limited to a brief window of time for going back to the past – typically between 30

minutes and four hours.

Start-over

Also known as Restart TV

Use case: Press a dedicated button to go back to the beginning

of the current program. Time-shifting features are enabled to browse the

stream from the beginning of the current program to the real time.

Usage constraints: The point at which a program starts must be known by the system, typically from the EPG, for the

service to be delivered. The precision of the start-up depends on the information used to tag the beginning of a program. It is

more precise with an in-line trigger than with an EPG.

Catch-up TV

Also known as Replay TV

Use case: From a backward EPG, select a program to display.

Usage constraints: The accuracy of the start-up time depends on the

information used to tag the beginning of a program. It is more precise with an in-line trigger than with an EPG, which precision does not usually exceed the minute.

The amount of content or storage used can be limited in the local device or contractually.


Cloud PVR – Program oriented

Also known as Network-PVR, EPG-based PVR, Virtual PVR

Use case: From the EPG, select a program to record. Access the program as on-demand content. The recording can be accessed the instant it has

started on the live channel.

Usage constraints: The precision of the recording depends on the information used to tag the beginning and the end of a

program. It is more precise with an in-line trigger than with an EPG. The program must be made available while it is being recorded. The amount of content or storage used is limited in case of private copy but can be unlimited with

shared copy. It is possible that the content is only kept for a given duration.

Cloud PVR – Time-based oriented

Impulsive recording

Also known as Red button recording, instant recording

Use case: The user presses the record button and selects a

recording duration. The user presses the record button to record the

current event. The recording can be accessed from the instant it has started on the live channel.

Usage constraints: The amount of content or storage used is limited in the case of private copy but can be unlimited with

shared copy. It is possible that the content is only kept for a given duration.

Scheduled recording

Also known as Time-oriented recording

Use case: Using a scheduler, the user selects a beginning and an

end-time to record the content of a channel. The recording can be accessed from the instant it has

started on the live channel.

Usage constraints: Same as impulsive recording


Cloud PVR solution benefits The cloud PVR approach has many benefits compared with the local PVR, for both service operators and end-users. The benefits are even bigger when shared copy is allowed.

Solution benefits for the end-users

Standard benefits:

Multiple recordings: Users can launch any number of recordings on various channels simultaneously, without any constraint on the available bandwidth or number of tuners on their reception device.

Flexible quota: The quantity of storage available is not limited to the one bought at the time of the STB. Storage can be increased by the operator, as needed.

Reliability: The content remains available in the cloud, despite what happens to the reception device.

Multi-STB and multiscreen availability: The recorded content can be made available on all of a subscriber’s devices.

Quality with adaptive bitrate: The quality of the recorded content is not submitted to the constraints on the network at the time of the recording. With local PVR, if the network quality is not good at the time of the recording, the content will be stored with a low quality. With cloud PVR, the content can be adapted to the conditions at stake at the time of the streaming.

Additional benefits with shared copy:

Enhanced quality of experience: With private copy cloud PVR, duplicating all the layers of content for each user would place a huge constraint on an operator’s resources, making it necessary to reduce the number of qualities available, which has an impact on the quality of experience (QoE). With shared copy cloud PVR, the content can be made available with all the layers.

Record past programs: If the feature is enabled by the operator, end-users can request the recording of any program that has already started, which is not possible with private copy where all the content may not have been recorded and where each copy is only available to the subscriber who has requested it.

Solution benefits for service operators

Standard benefits:

Hard drive cost savings: There is no need to deploy PVR STBs with a storage space that is not always used.

Support cost savings: Disks in a STB are an important point of failure. With the cloud approach, calls to support center and replacement requests are reduced.

Reduced churn: Customers that have recorded all their content in your network are less willing to switch to a new operator.

New business models: Storage space in the cloud can be charged in various ways (e.g., global fee per month, price per channel or bouquet, storage quotas, etc.).

Targeted ads: They can be inserted in the network for pre-roll or mid-roll scenarios, and they can be personalized per user.


Additional benefits with shared copy:

Further costs savings: The possibility of consolidating the storage among all users brings extra cost reduction. It also greatly simplifies the management of a storage space per user, since this complexity can be avoided. From an economical point of view, shared copy is the scenario that makes the most sense for cloud PVR.

Technologies

Shared copy/private copy

Despite the fact that recording live content onto a physical DVR in the end-user household is not very different from recording it via a service provided in the cloud, and that there is an obvious economical advantage of doing it in the cloud, service operators have been reluctant to roll out cloud PVR due to the copyright laws.

These laws are evolving at a different pace in various regions of the world, allowing more flexibility to the recording system.

In the United States, it has been difficult to put in place an agreement with content owners, yet a recent Cablevision case showed that cloud PVR in its private copy model can legally exist. Comcast, with the launch of its X1 DVR service, also demonstrated that this could become a reality. In Europe, it seems easier or at least quicker to acquire the rights for cloud PVR. In addition, some countries legally allow the shared copy model. Some deployments have already taken place in Sri Lanka, Singapore, Switzerland and Iceland.

Shared copy model

Shared copy model, also known as unique copy model, is largely supported when it comes to EPG-based recording use case. In this model, recording is done based on the start and end time referenced in the electronic program guide. If several users want to record the same program, a unique copy can easily be created. Supporting a shared copy model that allows time-based and impulsive recording is another story. In these cases each end-user request might be done with different begin and end dates.

To avoid duplicating the recording, the cloud PVR solution has to aggregate all the end-user requests and decide which part of the live content has to be recorded to ensure that each piece of content is recorded only once. This is known as the advanced shared copy model. The advanced shared copy model optimizes the bandwidth on the storage media and enables CDN caching of the recorded content. This is the most high-performance and cost-effective solution for cloud PVR deployment.

Broadpeak’s cloud PVR solution is designed to support the advanced shared copy model. With its unique recording method, the solution enables EPG-based and time-based recording, including impulsive recording for both IPTV (TS format) and OTT (adaptive bitrate format) content.

« Copyright laws are evolving at a different pace in various regions of the world, allowing more flexibility to the recording system. »


Private copy model

In a private copy model, each end-user recording request leads to a true recording on the system. The limitations of this model can be real obstacles for operators wanting to roll out cloud PVR:

It requires a large amount of bandwidth between the origin servers and the storage for recording (linked to the number of users).

It requires a large amount of storage for storing one copy of the content per user (linked to the number of users).

Each piece of recorded content is unique and, by essence, not cacheable by a CDN, which increases the load on the backbone and consumes a significant amount of bandwidth.

However, due to different interpretations of laws or agreements in place with content providers, several optimizations of the pure private copy model can be proposed to overcome the main limitations of the traditional private copy model.

Option 1

The content is recorded only once on storage by the origin server.

One physical file per end-user is created on storage by duplicating the original copy.

Option 2

The content is recorded only once on storage by the origin server. One physical file per end-user is created on storage by duplicating

the original copy. The origin server delivers the original copy for each end-user.

Option 3

The content is recorded only once on storage by the origin server.

A virtual file is created on storage by cloning the original file, associating one filename to each end-user.

The streaming is done using the filename associated to each end-user.

Option 4

The content is recorded only once on storage by the origin server. A virtual file is created on storage by cloning the original file,

associating one filename to each end-user. The origin server delivers the original copy for each end-user.


Benefits of the different options to optimize the private copy model

Benefits Legal usage of a fully private copy (a)

Preserves bandwidth between origin servers

and storage (b)

Allows CDN caching for bandwidth optimization

(c)

Optimizes amount of storage necessary

(single copy storage) (d)

Option 1 Option 2

Option 3

Option 4

(a) From a legal perspective, each end-user has and uses his own copy

(b) Avoid overloading the network interface between the origin server and storage, and limit the number of origin servers and storage nodes required to sustain the writing bandwidth needed by the private copy model.

(c) Efficient caching inside the CDN, the origin server delivers the same copy for each end-user.

(d) Optimization in term of storage size (only one real copy is stored).

Broadpeak’s cloud PVR solution gives service operators different ways to optimize the private copy model, allowing them to roll out the best cloud PVR services in compliance with the copyright laws in their countries.

Recording methods

Traditionally, two different methods are used to record live content: the DVR window mode, also known as circular buffer or rolling buffer, and the asset recording mode.

A third method is now emerging. The strength of this new solution is to combine the best of these two solutions to optimize time-based recording and support impulsive recording use cases.

Traditional DVR window mode recording

This method is based on a DVR window on the origin server. For each live channel, the origin server manages a circular buffer where the channel is continuously recorded. Usually, the depth of this DVR window is configurable and can vary from minutes to weeks.

When end-users want to watch a program available in the circular buffer, they have to request the origin server with the UTC begin and optionally the end time on a particular channel.

The main advantage of this method is that if some EPG updates occur before or after the end of the program recording, as long as the new program dates are available in the DVR window, they are automatically taken into account since it is the end-user request (via the TV portal) that drives the program playback begin and end time inside the DVR window.

DVR window mode recording


Traditional asset mode recording

This second recording method is based on a record request sent by a third-party component, usually the service platform or the content management system. When receiving this request, the origin server in charge of the live channel recording records the corresponding channel using the begin and end time information provided by the service platform. The live program is recorded in a dedicated file. The main limitations of this method are:

It does not support EPG update. When the content recording is finished, it is not possible to update the beginning and the end date of the recorded TV program.

If several record requests include the same piece of content, the content is recorded several times on the storage.

When end-users want to watch a program, they have to request the delivery, similar to VOD delivery, using the filename of the recorded program.

The new combination of DVR window mode and asset mode recording

This new recording method combines the DVR window with the asset mode recording, enabling a growing buffer of recorded content.

For each channel to be recorded, a DVR window is configured on the origin server in charge of the live channel recording. The DVR window depth is configurable per channel, and its duration can go up to several days. This DVR window is used to deliver short-tail services such as cloud time-shifting, start-over, and catch-up TV without the need to receive any request from the service platform or the content management system. In this DVR window, the recorded live content is split into segments of equal length.

For long-tail services such as cloud PVR, a portion of these segments can be kept on the storage and make the recording buffer grow. To flag these segments as “to be kept,” a recording request must be received from the service platform or the content management system. A software module, the “record manager,” has to be able to receive and aggregate all end-user requests, decide what segments must be kept, and return an asset identifier for each request, which is in turn used for the recording playback. The record manager then schedules the requests to be sent to the origin/capture servers to keep the right segments on the storage.

Asset mode recording

Growing buffer mechanism


The main advantages of the solution are the following:

As long as the cloud PVR content is in the DVR window, it is possible to update the begin date and the end date of the recording.

Enable advanced shared copy model for time-based and impulsive cloud PVR thanks to its ability to store the same piece of content only once, even if multiple users want to record it.

Broadpeak’s cloud PVR solution supports this enhanced recording method for both IPTV (TS format) and OTT (adaptive bitrate) content.

Specific features

Content protection

For IPTV and cable deployments, live channels are recorded “as is” with conditional access system (CAS) protection. The main advantages are simplifying the key management workflows and keeping the same level of security for the recorded content as what is available for the live content. As the live streams are fully encrypted some specific descriptors or a specific field must be available in the MPEG-2-TS content (DVB AU descriptor or random access indicator) to allow picture indexation, which enables the trick mode feature. This data must be added by the live encoder in the MPEG-2-TS IPTV/Cable live channels.

For ABR format, two options are possible depending on the use of a pivot format to store the content or not. If the entire delivery formats are stored, they can be then recorded “as is” with digital rights management (DRM) protection. If only a pivot format is stored and is used to generate the various delivery format flavors on session request, then this pivot format should be stored in the clear to allow reprocessing. DRM protection will be then applied per session during the content packaging to protect the different streaming formats. To avoid a lack of security, the pivot format can be stored encrypted using AES algorithm and will be decrypted before the “On-The-Fly” packaging process.

From the service operator perspective, the management approach that is chosen should be based on the business model:

Recorded content freely available if part of a live bouquet to which the user has already subscribed

New subscription to access recorded content

Limited availability according to date

Etc.

Broadpeak’s cloud PVR solution is agnostic to the content protection for IPTV and cable MPEG-2-TS live content. For ABR content, Broadpeak’s cloud PVR solution is able to record the content either as it is or apply a DRM protection during “On-The-Fly” packaging.


Scalability management

Horizontal scalability

A cloud PVR solution must scale to handle:

The growth of the number of channels to record (i.e., ingest capacity);

The growth of the number of recording requests (i.e., recording and storage capacity); and

The growth of the number of viewing requests (i.e., playback capacity).

The last two factors are mainly linked to the growth in terms of end-users and/or their engagement with the cloud PVR services, the usage model. Their weight also depends on the recording model, whether it is a shared or private copy model. The growth of each factor must be handled separately in order, for example, to avoid that adding playback capacity or ingest capacity, requires adding storage capacity.

Broadpeak’s cloud PVR solution offers a high level of flexibility to answer all the constraints of the different cloud PVR use-cases and usage model, making it easier for service operators to manage capacity planning. The scalability is managed in a horizontal way, allowing the system to grow step by step according to the evolution of each project’s requirements.

“On-The-Fly” packaging

Cloud PVR, especially when used in a multiscreen offering, requires a huge amount of storage. Each piece of recorded content must be available in the various delivery formats supported by the range of devices addressed by the service operators. Recorded content may thus have to be available in the four major formats used today to address the majority of the smartphones, tablets, PCs, connected TVs, and game console devices. These formats are Apple HTTP Live Streaming (HLS), Microsoft HTTP Smooth Streaming (HSS), Adobe HTTP Dynamic Streaming (HDS), and MPEG-DASH. Storing the same recording in all of these different formats in advance is costly and can become an obstacle for operators to rollout cloud PVR. A way to overcome this challenge is to use “On-The-Fly” packaging (OTF).

With OTF packaging, the recording is stored in only one format, preferably protected with an AES fixed key (DRM is not applicable), or in the clear in a format usually named “pivot format.” It is only packaged in the right format and protected using the DRM of the choice of the operator by the origin server when requested by an end-user device.

According to Cablevision1, more than 60 percent of recordings are viewed within the first two days following the recording. This implies that the popularity of recorded content is at the highest soon after the content availability, and it decreases very rapidly. While during the first two days it is optimal to store everything to avoid continuous processing, long-tail content should not be stored in all formats.

1 REMOTE STORAGE DVR Stephanie Mitchko Cablevision Systems LLC


The trade-off between processing and storage must be found dynamically by setting up thresholds that allow switching between both modes.

In order to keep the same architecture for both popular and non-popular content, the capabilities of an origin server, which are usually weak in terms of I/O, have to be boosted with an origin cache (a.k.a shield cache) that only stores popular content. This is a key component to preserve the equipment and can be achieved with Broadpeak’s BkS400 caching server and the BkS300 origin server.

Redundancy management

Redundancy management is an important point for service operators to consider when rolling out a cloud PVR solution. However, redundancy in a cloud PVR solution can be costly because all of the recorded channels have to be ingested in the origin server cluster twice when a 2N redundancy scheme is used. This may lead to double the recording capacity of the origin server cluster.

To reduce the cost of the solution, an N+1 redundancy scheme is also possible, but with the major limitation that part of the recordings will be lost during the time required to set up the live channel on the redundant origin server in case of failure.

However, in a 2N redundancy scheme, some optimizations are also possible to avoid recording the same live channels twice. Even if two different origin servers ingest the live channel, only one can actually write the data. To avoid any loss of video data and offer the best quality of experience, Broadpeak recommends a 2N redundancy scheme.

Broadpeak’s cloud PVR solution supports an architecture where a live channel is ingested by two origin servers but actually recorded by the main origin server. In case of failure of the main origin server, the recording can be resumed by the redundant one without any loss of video data, ensuring the best possible quality of experience without requiring doubling the writing bandwidth and the storage capacity of the system.

Note: Other options are possible if the Encoder cannot push video content to two origin servers (load-balancer).


Broadpeak solution is available for IPTV/cable networks and OTT.

Broadpeak unified Cloud PVR solution

Broadpeak’s cloud PVR solution is designed for IPTV/cable networks with transport stream content (MPEG-2-TS) format as well as OTT with adaptive bitrate (ABR) formats.

For IPTV/cable networks, live content recording is managed by Broadpeak’s BkS100 capture and streaming server.

For OTT, live content recording is managed by either Broadpeak’s BkS300 origin server or Broadpeak’s BkS350 origin packager.

Broadpeak’s BkM100 and record manager offer a unified API toward the service platform or content management system to pilot its cloud PVR solution for any delivery format.

Broadpeak Solution


Number of playouts for Cloud PVR channels

The experience of one of Broadpeak’s customers with the Cloud PVR service

One of Broadpeak’s European customers has launched its Cloud PVR service in January 2013 for its 60,000 customers. In 2 years, this service has become very popular. In December 2014, they had over 2 million playouts for their cloud PVR channels.

Broadpeak’s customer has seen concurrent streams go up to 8,200 during the peak hours on Sunday nights, both for VoD and cloud PVR. Amongst these streams, around 80 % are cloud PVR.

video recording in the cloud: use cases and...

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