This document describes the current method of setting DRM keys using an additional stage to dynamically generate ISM manifests. This will be deprecated as part of on-going development of new DRM functionality (multiple keys, key rotation, etc.)
Remix VOD enables server side mixing of content to produce a single output stream. Clients and playback devices see the stream coming from a single origin and having a timeline without any discontinuities.
The solution makes use of two Unified Streaming Platform products:
- Remix, to create a single presentation from multiple input sources
- Origin, for Just-In-Time packaging/transmuxing to all supported streaming formats
Remix VOD allows for the following use cases:
- Bumper for Everyone (Ratecard, Dubcard, Promo)
- Virtual Subclips (Highlights or Skip-over)
- Pre-, Mid-, Post-Roll (VOD)
Playout Origin for content, this takes the remixed MP4 created by Remix and plays out all streaming formats, optionally with DRM applied.
Uses Apache mod_ext_filter and mod_proxy_http to proxy requests to Remix and run mp4split to generate an ISM on the fly with DRM keys and other options.
Based on a SMIL playlist Remix compares the listed sources and produces a single remixed MP4.
Creates a playlist based on a request URL.
This is the most important integration point as it provides the mapping of a request URL to the source media that will be used to produce the final presentation.
The ISM, Remix and SMIL generation processes can be relatively intensive, so caching proxies are used to reduce latency and minimise unnecessary load.
This can be any HTTP caching proxy, e.g. Apache httpd with mod_cache and mod_proxy, NGINX, Varnish.
The SMIL Origin must return a SMIL 2.0 (Synchronized Multimedia Integration Language) playlist.
SMIL functionality supported by Remix¶
- 'outputDescription' meta element in head to point to target profile
- Without setting this, the first clip in the playlist will be used for the target profile
- 'seq', sequence of clips to playout
- 'par' combine multiple files into a single clip as part of the sequence, e.g. if different bitrates are stored in separate source files
- 'clipBegin', 'clipEnd', to select only parts of the clip rather than whole
- currently only supports using the "wallclock(ISO 8601)" format, not all formats included in SMIL 2.0
- can also be applied to 'par' elements, as an extension
A SMIL playlist for a simple use case that will play a pre-roll bumper and 30 seconds of Tears of Steel looks like this:
<?xml version="1.0" encoding="utf-8"?> <smil xmlns="http://www.w3.org/2001/SMIL20/Language"> <head/> <body> <seq> <video src="http://sample-content/logo_5s_dref.mp4"/> <video src="http://sample-content/tears-of-steel-dref.mp4" clipEnd="wallclock(1970-01-01T00:00:30.000Z)"/> </seq> </body> </smil>
An example for a use case with pre- and mid-roll advertisements using Sintel as the main content, targetting Sintel for the output profile:
<?xml version='1.0' encoding='UTF-8'?> <smil xmlns="http://www.w3.org/2001/SMIL20/Language"> <head> <meta name="outputDescription" content="http://storage/main/sintel/sintel_dref.mp4"/> </head> <body> <seq> <video src="http://storage/ads/origin/origin08_x264.mp4"/> <video src="http://storage/main/sintel/sintel_dref.mp4" clipEnd="wallclock(1970-01-01T00:00:30.000Z)"/> <video src="http://storage/ads/capture/capture10_x264.mp4"/> <video src="http://storage/main/sintel/sintel_dref.mp4" clipBegin="wallclock(1970-01-01T00:00:30.000Z)" clipEnd="wallclock(1970-01-01T00:01:00.000Z)"/> </seq> </body> </smil>
An example based on different bitrates in separate MP4s, using <par> to combine these MP4s into a single item:
<?xml version="1.0" encoding="utf-8"?> <smil xmlns="http://www.w3.org/2001/SMIL20/Language"> <head> </head> <body> <seq> <par> <video src="http://storage/path/to/files/file_1280.mp4" /> <video src="http://storage/path/to/files/file_1024.mp4" /> <video src="http://storage/path/to/files/file_768.mp4" /> <video src="http://storage/path/to/files/file_480.mp4" /> </par> <video src="http://local-storage.unified-streaming.com/demo/tears-of-steel/tears-of-steel-teaser-no-jpg.ism" /> </seq> </body> </smil>
Storage for Remix VOD can consist of any form of attached storage (a mount point on the filesystem) or HTTP accessible storage such as S3.
The only requirement is that content must be accessible at the same path from both Remix Origin and Unified Origin, e.g. if using network attached storage mounted to /storage, the mount must be the same on all Remix Origins and Unified Origins.
Remix VOD is flexible when it comes to deployment options, as both Unified Origin and Remix are stateless and work over HTTP. This means it can easily be deployed on both physical or virtual hosts, or using container technology such as Docker.
Our GitHub Remix Demo has each component running in a separate Docker container, and uses Docker Compose to deploy and configure them to produce a working environment.
Supported OS and software versions¶
Remix requires Apache 2.4.x.
Recommended OS and web server versions are:
|Alpine Linux v3.11||Apache/2.4|
Remix VOD can be deployed using various approaches:
- Bare metal
- Virtual machines as for instance Amazon EC2
- Container environments managed by for instance Kubernetes
- Content encoding profiles should match
- Remix uses a set of heuristics to make "best fit" matches of tracks between separate source media
- Video aspect ratio changes can cause playback quality issues depending on the player as it may stretch the content to fit the expected aspect ratio
- Some audio differences will cause playback to break and so cannot be
matched, for example,
- sample rate mismatch
- channel count difference