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Transcoding - Why Is It Vital for Streaming
If you’re thinking about streaming media, you probably fall into considered one of camps: Either you already know something about transcoding, or you’re wondering why you keep hearing about it. In case you aren’t certain you need it, bear with me for a number of paragraphs. I’ll explain what transcoding is (and isn’t), and why it may be critical on your streaming success — especially 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; and then somehow altering and recompressing it. For instance, you might change the audio and/or video format (codec) from one to another, akin to changing from an MPEG2 supply (commonly utilized in broadforged television) to H.264 video and AAC audio (the most popular codecs for streaming). Other primary tasks might include adding watermarks, logos, or other graphics to your video.
Transrating refers specifically to altering bitrates, reminiscent of taking a fourK video enter stream at 13 Mbps and converting it into one or more decrease-bitrate streams (also known as renditions): HD at 6Mbps, or different renditions at three Mbps, 1.eight Mbps, 1 Mbps, 600 kbps, etc.
Transsizing refers specifically to resizing the video frame; say, from a resolution of 3840×2160 (fourK UHD) down to 1920×1080 (1080p) or 1280×720 (720p).
So, once you say "transcoding," you may be referring to any combination of the above tasks — and typically are. Video conversion is computationally intensive, so transcoding usually requires more powerful hardware resources, together with faster CPUs or graphics acceleration capabilities.
What Transcoding Is Not
Transcoding shouldn't be confused with transmuxing, which will also be referred to as repackaging, packetizing or rewrapping. Transmuxing is if you take compressed audio and video and — without changing the actual audio or video content material — (re)package it into different delivery formats.
For example, you may need H.264/AAC content material, and by changing 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 far smaller than for transcoding.
When Is Transcoding Critical?
Merely put: Transcoding is critical whenever you want your content to achieve more finish users.
For instance, let’s say you want to do a live broadforged utilizing a camera and encoder. You could be 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. However for those who attempt to stream it directly, you will have a number of problems. First, viewers without ample bandwidth aren’t going to be able to view the stream. Their players will be buffering consistently as they wait for packets of that 1080p video to arrive. Secondly, the RTMP protocol is no longer widely supported for playback. Apple’s HLS is much more widely used. Without transcoding and transmuxing the video, you will exclude nearly anybody with slower data speeds, tablets, mobile phones, and connected TV devices.
Using a transcoding software or service, you possibly can simultaneously create a set of time-aligned video streams, each with a distinct bitrate and frame size, while changing the codecs and protocols to reach additional viewers. This set of internet-pleasant streams can then be packaged into several adaptive streaming formats (e.g., HLS), permitting playback on almost any screen on the planet.
Another widespread instance is broadcasting live streams utilizing an IP camera, as can be the case with surveillance cameras and site visitors cams. Once more, to succeed in the largest number of viewers with the absolute best quality allowed by their bandwidth and gadgets, you’d need to support adaptive streaming. You’d deliver one HD H.264/AAC stream to your transcoder (typically located 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 is likely to be the same server as your transcoder) package these renditions into one or more adaptive streaming codecs before delivering them to finish users.
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