Transcoding – Why Is It Vital for Streaming Leave a comment

If you happen to’re thinking about streaming media, you probably fall into one in all camps: Either you already know something about transcoding, or you’re wondering why you keep hearing about it. For those who aren’t certain you want it, bear with me for a couple of paragraphs. I’ll clarify what transcoding is (and isn’t), and why it might be critical on 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 term that covers a number of digital media tasks:

Transcoding, at a high level, is taking already-compressed (or encoded) content material; decompressing (decoding) it; and then somehow altering and recompressing it. For example, you would possibly change the audio and/or video format (codec) from one to another, reminiscent of changing from an MPEG2 source (commonly utilized in broadcast television) to H.264 video and AAC audio (the preferred codecs for streaming). Different fundamental tasks may embody adding watermarks, logos, or different graphics to your video.

Transrating refers specifically to changing bitrates, such as taking a 4K video input stream at thirteen Mbps and changing it into one or more decrease-bitrate streams (additionally known as renditions): HD at 6Mbps, or different renditions at three Mbps, 1.8 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, when you say “transcoding,” you is likely to be referring to any mixture of the above tasks — and typically are. Video conversion is computationally intensive, so transcoding normally requires more highly effective hardware resources, together with 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 while you take compressed audio and video and — without changing the precise 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 possibly can deliver it as HTTP Live Streaming (HLS), Easy 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?

Merely put: Transcoding is critical while you want your content material to achieve more end users.

For example, let’s say you need to do a live broadsolid utilizing a camera and encoder. You could be compressing your content with a RTMP encoder, and select the H.264 video codec at 1080p.

This must be delivered to on-line viewers. However for those who try to stream it directly, you will have a number of problems. First, viewers without enough bandwidth aren’t going to be able to view the stream. Their players will be buffering always 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 far more widely used. Without transcoding and transmuxing the video, you will exclude nearly anyone with slower data speeds, tablets, mobile phones, and connected TV devices.

Utilizing a transcoding software or service, you’ll be able to concurrently create a set of time-aligned video streams, every with a distinct bitrate and frame measurement, while changing the codecs and protocols to succeed in 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 instance is broadcasting live streams using an IP camera, as would be the case with surveillance cameras and visitors cams. Once more, to reach the biggest number of viewers with the best possible quality allowed by their bandwidth and gadgets, you’d want to support 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 definately’d have your media server (which may be the identical server as your transcoder) package these renditions into one or more adaptive streaming formats before delivering them to finish users.

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