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Ott Streaming Protocols and DRM
- 1. OTT STREAMING PROTOCOLS AND DIGITAL RIGHTS MANAGEMENT (DRM) MUHAMMED ASIM YILDIZ
- 2. WHAT IS A STREAMING PROTOCOL? A Streaming Protocol is: A standardized delivery method for breaking video into chunks Sending it to the viewer Reassembling it on the viewer
- 3. WHY NEED STREAMING PROTOCOLS? Most digital video is designed for: Storage (small file sizes) Playback (universal playback) Most standart video formats are not designed for streaming In order to stream a video: Video needs to be converted to a streamable file A streamable file consists of chunks These chunks arrive sequentially and playback as recevied
- 4. STREAMING PROTOCOLS ADVANTAGES Streaming protocols can get much more complex Many are “adaptive bitrate” protocols Deliver the best quality that a viewer can support at any given time Some protocols focus on “reducing latency” Some protocols “delay” between an event and viewer Some protocols focus on “DRM” Some protocols work only on certain systems
- 5. PROTOCOL – CODEC – CONTAINER FORMAT Codec refers to “Video Compression Technology” Different codecs are used for different purposes For example: Apple ProRes is often used for video editing H.264 is widely used for online video
- 6. PROTOCOL – CODEC – CONTAINER FORMAT Format simply refers to container format of a video file .mp4, .m4v, .avi, .mkv A container format is like a “box” that contains: A video file An audio file Metadata Container format isn’t a central concept for live streamers
- 7. STREAMING IN REAL-LIFE Imagine that you’re a merchant, and you’re transporting clothing in bulk The clothing represents the video content The streaming codec is the machine that compresses the clothing into a bundle to save space The container format is the boxcar that these bundles are packed inside The streaming protocol is analogous to the railroad tracks, signals, and drivers who deliver it to the destination
- 8. STREAMING IN OTT Generate multiple versions of the same content (e.g. different bitrates, spatial resolutions) Chop these versions into segments (e.g. two seconds) The segments are stored in a web-server and can be downloaded with HTTP GET requests The relationships between different versions is described by a manifest file The manifest file is provided to the client prior to the streaming session Manifest represents different qualities of the media content Manifest has individual segments of each quality with URLs This structure allows to bind to segments to the bitrate, among others (start time, duration of segments)
- 9. STREAMING PROTOCOLS HTTP LIVE STREAMING (HLS) DYNAMIC ADAPTIVE STREAMING over HTTP (MPEG-DASH) MICROSOFT SMOOTH STREAMING (MSS) REAL-TIME MESSAGING PROTOCOL (RTMP) WEB-RTC SECURE RELIABLE TRANSPORT (SRT) REAL-TIME STREAMING PROTOCOL (RTSP)
- 10. HTTP LIVE STREAMING HLS Apple created it in 2009 Built to drop Flash from iPhones Supported by: Desktop browsers Smart TVs Android and iOS mobile devices HTML5 players also natively supports
- 11. HTTP LIVE STREAMING HLS HLS supports: Adaptive-bitrate streaming (High Quality) Supports the common H.264 codec Supports latest H.265 codec Secure streaming The major downside is high latency
- 12. DYNAMIC ADAPTIVE STREAMING OVER HTTP MPEG-DASH The only international standardized solution Created in 2012 Currently adopted by YouTube, Netflix etc. Most big companies have contributed to standardization
- 13. DYNAMIC ADAPTIVE STREAMING OVER HTTP MPEG-DASH MPEG-DASH supports: Adaptive-bitrate streaming (High Quality) Codec agnostic (can be used with almost any streaming encoding) It supports standards-based APIs for browser based DRMs: Encrypted Media Extensions (EME) Media Source Extensions (MSE) The major downside is no compatibility with Apple Devices/iOS
- 14. MICROSOFT SMOOTH STREAMING MSS Microsoft created it in 2008 Targeting the smooth delivery of HD contents over IIS Based on fragmented MP4 files
- 15. MICROSOFT SMOOTH STREAMING MSS MSS supports: Adaptive-bitrate streaming (High Quality) Includes CPU utilization for adaptive-bitrate streaming Supports the common H.264 codec The major downside is MSS limits the use of Smooth Streaming to CDNs using Microsoft Products
- 19. DIGITAL RIGHTS MANAGEMENT DRM DRM refers to the algorithms and processes DRM enforces copyright compliance when consuming video content Without DRM, content can be easily copied DRM is not visible to the consumers DRM is also used offline to provide copyright protection for CDs, DVDs, and BluRays
- 20. DRM TECHNOLOGIES Fairplay: Cipher Block Chaining encryption The only option for Safari and is only used by Apple devices Widevine: Developed by Widevine Technologies, bought by Google Used on Android Devices natively, in Chrome, Edge (soon), Roku, Smart TVs PlayReady: developed and maintained by Microsoft Supported on Windows, most set-top boxes and TVs
- 21. DRM TECHNOLOGIES
- 22. DRM TECHNOLOGIES
- 24. DRM IN OTT?
- 27. DRM ENCRYPTION KEYWORDS COMMON MEDIA APPLICATION FORMAT (CMAF) There are primarily two protocols in use today – MPEG-DASH and HLS MPEG-DASH uses the mp4 container and HLS uses the MPEG-TS (ts) container for its video files Duplicate contents (doubled storage size) When also adding DRM If we use the 3 hypothetical DRM providers with 3 different encryption standard, then we need 2*3=6 copies of the video The CMAF specification was created Store files in the fragmented mp4 container format (fmp4) With support from both MPEG-DASH and HLS, we now create only one set of videos, store it in fmp4 format
- 28. DRM ENCRYPTION KEYWORDS COMMON ENCRYPTION SPECIFICATION (CENC) If different DRM technologies use different encryption standards We still need to store multiple copies of each file For this purpose, the MPEG developed the CNEC Videos can be encrypted using either CENC (AES-128 Counter-CTR) or CBCS (AES-128 Cipher Block Chaining-CBC) The implication of CENC A content provider needs to encrypt videos only once and any decryption module can decrypt it Note: Exposing the encryption algorithm is not a problem as long as the keys are strongly protected.
- 29. DRM ENCRYPTION KEYWORDS ADVANCED ENCRYPTION STANDARD (AES) AES is a symmetric-key algorithm: encryption and decryption are performed using the same key It has three variants based on the key-length: 128, 192, and 256 bits. The longer the key, the harder it is to crack. Cracking the AES-128 without the key would require a “billion times a billion years” and a super- computer
- 30. HOW DRM WORKS? ENCRYPTION Communications between the requesting playback software and the license server are encrypted Each segment is encrypted according to the MPEG Common Encryption (CENC) specification The MPEG-CENC standard is comprised of XML style formats The MPEG-CENC standard requires a minimum of a key and key id to run Standard content encryption is done according to the Advanced Encryption Standard (AES) Using 128-bit keys and a Cipher Block Cipher block is either Counter Mode (CTR) or Cipher Block Chaining (CBC) Only the audio and video data within a segment is encrypted
- 32. DRM DECRYPTION KEYWORDS ENCRYPTED MEDIA EXTENSIONS (EME) Encrypted Media Extensions (EME) is a JavaScript API EME is an extension to the HTMLMediaElement specification EME provides an API that enables web applications to interact with content protection systems EME allows playback of encrypted audio and video EME is designed to enable the same app and encrypted files to be used in any browser, regardless of the underlying protection system
- 33. DRM DECRYPTION KEYWORDS CONTENT DECRYPTION MODULE (CDM) Content Decryption Module (CDM) is a software that decrypts and optionally, decodes + displays the video. Every DRM provider provides its own: Mechanism to create a license request (using the KeyID, device identifier, signing the request, etc.) Mechanism to understand the license response received from the DRM License Server (the response is encrypted too) and extract the decryption key Rules around storing the license locally on the client, license renewal, expiry, etc CDMs (Content Decryption Modules) is built into browsers such as Chrome, Firefox, Microsoft Edge, Safari
- 34. DRM FLOW Obtain the movie & its manifest from the CDN Extract the KeyID from the manifest Create the license request Send the license request to the license server Wait, listen, and receive the response from the license server. Use the decryption key from the server to decrypt the content Decode the decrypted content Display the decoded movie
- 37. HOW DRM WORKS? DECRYPTION When a web player identifies protected content: It calls on processes and interfaces defined by Encrypted Media Extensions (EME) Browsers will initiate a license request process License requests are generated by Content Decryption Module (CDM )(all of the decryption is done by CDM) Passed to the players through the EME (EME is just simply an interface) The player calls the appropriate function on the EME interface Then the sessions are updated by the CDM The EME interfaces with the CDM handles the decryption of the segments on browser or OS level
- 38. HOW DRM WORKS? CLIENT-SIDE The license acquisition using the EME starts from the playback client Creating a key session unique to the client, device, and the metadata found in the segments The CDM then generates a signed key message. The client then sends then secured message to the license server The license server returns the requested license With the resulting decision of whether or not the client is granted playback rights to the requested content If not, playback is halted and an error is shown. In successful communications scenarios, the client updates the session data with a returned license The content decryption is handled fully by the CDM In some circumstances, the license is cached for a set time and can be used to playback protected content offline The license and the decrypted data must not be accessible to clients other than the licensed content requester Therefore, the private keys and decrypted data are kept in a secure environment within the browser, operating system, and hardware (if supported), like Trusted Execution Environments.
- 39. THANK YOU MUHAMMED ASIM YILDIZ
Editor's Notes
- #3: Basically, protocols are technical processes that facilitate the transfer of data from one program to another. In streaming, this means the transfer of your video files to and from your encoder, streaming host, and eventually, the video player where your audience views your stream.
- #9: As a consequence, each client will first request the manifest that contains the temporal and structural information for the media content, and based on that information it will request the individual segments that fit best for its requirements. The adaptation to the bitrate or spatial resolution is done on the client-side for each segment, e.g., the client can switch to a higher bitrate – if bandwidth permits – on a per-segment basis, or to a lower bitrate – if bandwidth decreases. This has several advantages because the client knows its capabilities such as the received throughput, delay, device capabilities (e.g., screen resolution), etc. best.
- #12: H.265 codec, which delivers twice the video quality at the same file size as H.264.
- #13: Microsoft, Adobe, Apple, Samsung, Akamai, Cisco, Dolby, Ericsson, Qualcomm, Intel, Bitmovin
- #16: Microsoft also includes the CPU utilization as an indicator for the stream switching decision which is especially valuable for mobile devices such as smartphones and tablets. This means that if the CPU utilization is high, the client reduces the stream quality and resolution which furthermore reduces the CPU performance needs of the decoding process and guarantees a continuous decoding without stalls.
- #27: Adaptive bitrate technology on DRM
- #31: Encryption is a technique used to keep data confidential and prevent unauthorized people from reading it. Encryption uses a “key” to convert input data (plaintext) into an alternate form called ciphertext. It is almost impossible to convert the ciphertext back to plaintext without the key. However, practically speaking, decryption without the key is possible, and encryption algorithms are designed make reverse-engineering extremely expensive – in terms of time, money, and computing resources needed. Apple FairPlay supports only AES-CBC cbcs mode. HLS supports only AES-CBC cbcs mode (irrespective of CMAF) Widevine and PlayReady support both AES-128 CTR cenc or AES-128 CBC cbcs modes. MPEG-DASH with CMAF supports both AES-128 CTR cenc or AES-128 CBC cbcs modes. MPEG-DASH without CMAF supports only AES-128 CTR cenc mode. Similarly, when we encrypt a movie with a particular key, we need to create that association and provide that to the DRM license server (our receptionist, if you will). In DRM, a “KeyID” provides the association between an encryption key and a movie. It is a unique string of characters generated at the time of creating an encryption key for a particular movie. The Encryption Key and the KeyID are stored in a secure server (Key Store) that works alongside a DRM license server. When a client needs to play an encrypted movie, it requests the DRM license server for the decryption key by providing that particular movie’s KeyID. If the DRM license server is happy with the request (authentic request), it will ask the Key Store to provide the decryption key associated with that KeyID.
- #34: DRM vendors test and certify these CDMs to ensure that the license requests are formed correctly and as per specifications. they do not leak the decryption keys they do not leak the decrypted and decoded movies they securely store the decryption keys based on the license specifications (store the key for X days, for example) safely transport the video to the screen without leaking it For the above reasons, CDMs in browsers are closed-source, and this is a source of contention in the industry and public. They are not-trusted because the public cannot see what’s inside the CDM’s source code.
- #35: The player takes care of obtaining the movie, parsing the manifest, extracting the KeyID, making the requests to the DRM License Server, etc. A separate module (called the CDM or Content Decryption Module) takes care of creating the license request, decrypting & decoding the content. The video player is a JavaScript program that uses the EME APIs to transmit messages between the CDM and the License Server.
- #37: The player takes care of obtaining the movie, parsing the manifest, extracting the KeyID, making the requests to the DRM License Server, etc. A separate module (called the CDM or Content Decryption Module) takes care of creating the license request, decrypting & decoding the content. The video player is a JavaScript program that uses the EME APIs to transmit messages between the CDM and the License Server.
- #39: From the perspective of the content requester –..;....