Video Transcoding: Why is it Important in Livestreaming?6 min readReading Time: 5 minutes
In livestream, you may have come across the term ‘transcoding’. This is an important concept in modern media streaming technologes, especially when there is such a wide variety of playback devices and a growing consumption of online media.
Online video consumption has been unceasingly changing the media landscape. Video streaming increased from 19% in Q4 of 2019 to 25% in Q2 of 2020. With the availability of mobile devices and high-speed mobile internet connection, more people are turning into their small cell phone screens. In 2019, there were more than 175 million mobile media viewers in the U.S. That is approximately one in every two Americans.
You may have heard of the term ‘transcoding’. This is an important concept in video streaming, especially when there is such a huge variety and consumption of videos and media devices. Read on to find out what transcoding is, how it works, and why it is important.
What is Video Transcoding?
Transcoding, in the media context, means the process of converting a file from one format to another. It can be a file format, a video file, or an audio file. The outcome? For media viewers, this process makes video files available across different devices and platforms. For video producers, transcoding prevents placing a heavy strain on your computer due to large file sizes. And for streamers, it lifts the burden when you transfer or upload a video file to a website.
Why Do You Want to Transcode?
Imagine you have a media file of a two-hour movie with a size of 8 terabytes. Delivering such a large file on a website, let alone streaming to multiple devices and platforms, may cost you a lot of resources and even time. However, transcoding to a format with better compression can reduce the cost and difficulties when you deliver video content to a wide audience.
Here are three main reasons why transcoding is critical in video streaming and delivery:
- Your device or software doesn’t support the native format of your footage. If your video editing software or target device does not support your original file format, you’ll need to transcode it.
- The native footage takes up too much of your system resources. When your device does not have enough capacity to work on the original file, you’ll have to transcode the file to a lighter format. For example, you’re on a mobile device and want to watch an enormous 4K video.
- You have a file format that is obsolete or no longer supported by most modern media streaming devices (for example, HD DVD). To be able to play or work on those videos again, you’ll need to transcode that media file to a newer form of media.
Usage and Benefits of Transcoding
You can find the application of transcoding in many areas of content adaptation—that is, enabling one single media file to play across different devices. Mobile phone content adaptation is the most common use case of transcoding, especially when there’s a huge diversity of mobile devices.
Transcoding also applies to digital camera files. Files from most consumer digital cameras are transcoded to reduce the file size while maintaining the same quality.
A popular technology that involves transcoding is the Multimedia Messaging Service (MMS). This is the technology used to send or receive media messages such as image, sound, texts, and video via mobile phones. When you take a photo from your phone, for example, you’ll create a high-quality image of at least 640×480 pixels. If you send this image to another phone, the high-resolution image may be transcoded to a lower-quality file to fit the other’s device capacity. This reduction improves the experience on the recipient’s device (for example, faster load speed).
Another usage of transcoding is in home theater PC software to reduce disk space consumption. Video files are often transcoded from MPEG-2 to the H.264 or MPEG-4 format.
Offline and On-the-fly transcoding
There are two types of transcoding: offline and on-the-fly. Offline transcoding means you transcode files in advance. And on-the-fly, or real-time transcoding, means the process is happening as you’re watching the video.
Adaptive bitrate transcoding
Adaptive bitrate (ABR) is a critical technology of modern media streaming. ABR is a video streaming technique that detects the viewers’ bandwidth and device type, then dynamically adjusts the bitrates and resolutions of the video in real time. ABR allows all users to watch the same video file with reduced buffering, regardless of their network bandwidth or playback device.
In ABR, videos are stored on a server and transcoded in multiple different rates. Rather than having one single bitrate for a stream, ABR transcodes a file to various versions. There are tools that specifically provide this technology. But some streaming software programs like Castr livestreaming have the built-in adaptive bitrate feature that transcodes your media file to multiple formats as you stream, with zero setups needed.
Difference Between Transcoding and Encoding
“Transcoding” and “encoding” is often used interchangeably. But there’s a subtle technical difference between these terms. While both terms refer to the process of converting file formats, transcoding is converting a compressed media file, and encoding represents the conversion of an uncompressed video or audio file.
Another way to distinguish transcoding and encoding is that encoding takes an analog file and converts it to a digital format. Meanwhile, transcoding converts a digital file (or an already encoded file) into another digital format, for example, from a Flash file to an MP4.
- Transcoding: compressed, analog file to a digital file
- Encoding: uncompressed, digital file to another digital file
How Does Transcoding Work?
Transcoding involves two steps. First, your original media file must be decoded to an uncompressed file format (for instance, PCM for audio and YUV for video files). Next, the uncompressed file is encoded into the desired format.
There is another process called re-encoding or recoding.
In some cases, you may re-encode your data for several reasons. In video editing, if you want to edit files in a compressed format (edit on a JPEG image, for example), you will decode the file, edit, and re-encode it. This process removes the strain on your device during editing.
You may want to transcode to lower the bitrate of the media file without changing its file format, also known as ‘transrating’. This allows you to fit a media file into smaller storage space or over lower bandwidth. Transcoding can be used for image scaling, or known as ‘transsizing’. If your device is powerful enough, you can perform transsizing on playback.
File Types Used in Video Transcoding
Understanding different types of media files is essential when transcoding. You may often see terms like file formats, file types, and codecs.
File formats refer to how an audio or video file is stored on a computer system. A video file consists of a container, which has details like synchronization information, metadata, and subtitles.
A codec (a portmanteau of coder/encoder) refers to a device or software program that encodes or decodes a stream of digital data. In transcoding, video and audio codecs are the technologies used for data transmission, storage, encryption, and playback or editing.
Here is a list of the popular video file formats:
- MP4 (MPEG-4)
- MPEG2 PS, MPEG-2 TS
- LXF, GXF
Examples of video codecs:
- Windows Media 8