Should you’re thinking about streaming media, you probably fall into one in every of two camps: Either you already know something about transcoding, otherwise you’re wondering why you keep hearing about it. If you happen to aren’t positive you need it, bear with me for a number of paragraphs. I’ll explain what transcoding is (and isn’t), and why it might be critical for your streaming success — particularly if you want to deliver adaptive streams to any device.
So, What Is Transcoding?
First, the word transcoding is commonly used as an umbrella time period that covers a number of digital media tasks:
Transcoding, at a high level, is taking already-compressed (or encoded) content; decompressing (decoding) it; after which by some means altering and recompressing it. For instance, you may change the audio and/or video format (codec) from one to another, corresponding to converting from an MPEG2 supply (commonly utilized in broadforged television) to H.264 video and AAC audio (the most popular codecs for streaming). Other basic tasks may embody adding watermarks, logos, or different graphics to your video.
Transrating refers specifically to altering bitrates, akin to taking a 4K video input stream at 13 Mbps and changing it into one or more decrease-bitrate streams (additionally known as renditions): HD at 6Mbps, or other renditions at 3 Mbps, 1.8 Mbps, 1 Mbps, 600 kbps, etc.
Transsizing refers specifically to resizing the video frame; say, from a decision of 3840×2160 (4K UHD) down to 1920×1080 (1080p) or 1280×720 (720p).
So, when you say “transcoding,” you is likely to be referring to any combination of the above tasks — and typically are. Video conversion is computationally intensive, so transcoding often requires more highly effective hardware resources, including faster CPUs or graphics acceleration capabilities.
What Transcoding Is Not
Transcoding should not be confused with transmuxing, which may also be referred to as repackaging, packetizing or rewrapping. Transmuxing is once you take compressed audio and video and — without changing the actual audio or video content material — (re)package it into totally different delivery formats.
For example, you might have H.264/AAC content material, and by altering the container it’s packaged in, you can deliver it as HTTP Live Streaming (HLS), Clean Streaming, HTTP Dynamic Streaming (HDS) or Dynamic Adaptive Streaming over HTTP (DASH). The computational overhead for transmuxing is much smaller than for transcoding.
When Is Transcoding Critical?
Simply put: Transcoding is critical once you want your content material to achieve more finish users.
For example, let’s say you need to do a live broadforged using a camera and encoder. You is perhaps compressing your content material with a RTMP encoder, and select the H.264 video codec at 1080p.
This needs to be delivered to online viewers. But in case you try and stream it directly, you will have a few problems. First, viewers without enough bandwidth aren’t going to be able to view the stream. Their players will be buffering continually as they wait for packets of that 1080p video to arrive. Secondly, the RTMP protocol is not widely supported for playback. Apple’s HLS is much more widely used. Without transcoding and transmuxing the video, you will exclude virtually anybody with slower data speeds, tablets, mobile phones, and related TV devices.
Using a transcoding software or service, you may concurrently create a set of time-aligned video streams, each with a distinct bitrate and frame measurement, while converting the codecs and protocols to reach additional viewers. This set of internet-friendly streams can then be packaged into several adaptive streaming formats (e.g., HLS), allowing playback on nearly any screen on the planet.
One other widespread example is broadcasting live streams using an IP camera, as could be the case with surveillance cameras and traffic cams. Again, to succeed in the most important number of viewers with the best possible quality allowed by their bandwidth and gadgets, you’d wish to assist adaptive streaming. You’d deliver one HD H.264/AAC stream to your transcoder (typically positioned on a server image in the cloud), which in flip would create a number of H.264/AAC renditions at completely different bitrates and resolutions. Then you definitely’d have your media server (which might be the identical server as your transcoder) package those renditions into one or more adaptive streaming formats earlier than delivering them to end users.
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