The Complete Guide to Live Streaming:
Ingest and Transcoding
The fourth step in a live-streaming workflow is transcoding the stream into a variety of different codecs, bitrates, resolutions, and file containers. While this step can be skipped, it’s essential to most streaming scenarios.
A media server located either on premises or in the cloud ingests the packaged stream, and a powerful conversion process called transcoding ensues. This allows broadcasters to reach almost any device — regardless of the viewer’s connection or hardware. Once transcoding is complete, multiple renditions of the original stream depart for delivery.
Let’s take a look at how it works.
Transmuxing, Transcoding, Transizing, Transrating
To optimize the viewing experience across a variety of devices and connection speeds, broadcasters often elect to transmux, transcode, transrate, and transize streams as they pass through the media server.
- Transmuxing: Taking the compressed audio and video and repackaging it into a different container format. This allows delivery across different protocols without manipulating the actual file. Think of transmuxing like converting a word doc into a pdf and vice versa.
- Transcoding: An umbrella term for taking a compressed/encoded file and decompressing/decoding it to alter in some way. The manipulated file is then recompressed for delivery. Transrating and transizing are both subcategories of transcoding.
- Transrating: Changing the bitrate of the decompressed file to accommodate different connection speeds. This can include changing the frame rate or changing the resolution.
- Transizing: Resizing the video frame — or resolution — to accommodate different screens.
Rather than creating one live stream at one bitrate, transcoding allows you to create multiple streams at different bitrates and resolutions. That way, your live streams can dynamically adapt to fit the screen sizes and internet speeds of all your viewers. This is known as adaptive bitrate (ABR) streaming.
What Is Adaptive Bitrate Streaming?
Adaptive bitrate (ABR) streaming involves outputting multiple renditions of the original video stream to enable playback on a variety of devices and connection speeds. Content distributors use adaptive bitrate streaming to deliver high-quality streams to users with outstanding bandwidth and processing power, while also accommodating those lacking in the speed and power departments.
The result? No buffering or stream interruptions. Plus, as a viewer’s signal strength goes from two bars to three, the stream automatically adjusts to deliver a superior rendition.
How Does Adaptive Bitrate Streaming Work?
The first step to adaptive bitrate streaming is creating multiple renditions of the original stream to provide a variety of resolution and bitrate options. These transcoded files fall on an encoding ladder. At the bottom, a high-bitrate, high-frame-rate, high-resolution stream can be output for viewers with the most high-tech setups. At the top of the ladder, the same video in low quality is available for viewers with small screens and poor service.
During the process of transcoding, these renditions are broken into segments that are 2-10 seconds in length. The video player can then use whichever rendition is best suited for its display, processing power, and connectivity. If power and connectivity change mid-stream, the video will automatically switch to another step on the ladder.
With adaptive bitrate streaming, mobile viewers with poor connections don’t have to wait for the stream to load. And for those plugged into high-speed internet, a higher-resolution alternative can play.
Cloud-Hosted vs. On-Premises Streaming Platforms
Adaptive bitrate streaming requires a trusted video transcoding solution. Some content distributors install a media server software on their own servers — both on premises and in the could — while those who want to get up and running quickly without any hassles often prefer a managed cloud service.
But how do you make the choice between on-premises and cloud-based transcoding? Let’s take a look.