Transcoding

What is transcoding?

Transcoding is the process of taking a video file that’s been encoded, decoding it, making some kind of alternation to it, and then encoding it again. Since the encoding of data determines the type of compression, as well as the bitrate and resolution of the video, these are the things you can change during transcoding. 

How does transcoding work?

Let’s look at an example. You create a video using the MPEG-4 codec (a piece of software that got its name from its main function as coder-decoder). However, the source where you’re sending the file can only ingest files encoded with the H.264 codec. In that case, you would transcode it using the H.264 codec to get a file with a different type of compression. 

Other types of changes that happen during transcoding are more obvious since they affect the quality of video in a more immediate and visual way. These are:

• Transrating: a type of change where the bitrate of the video is lowered, reducing its quality and size for easier ingestion over lower-bandwidth connections. 
• Transsizing: a process of changing the resolution of the video, also reducing its quality and size and making it easier for ingestion over low-bandwidth connections.

What you can’t get while transcoding is a file with a different extension. That would require the change of the file format, and that’s not something that happens during transcoding. Transcoding changes the contents of the file. If you need to change the container, the process is called transmuxing.  

Encoding vs. transcoding

To better understand transcoding, it helps to know what encoding is as well. Encoding is the process of taking the data from the devices that capture video and audio information — your webcam, microphone, capture card, or streaming software — and converting it into a digital format you can send to streaming platforms. In a regular streaming setup, encoding plays a middleman role by helping the input and the output communicate. 

The encoder relies on a codec to dictate how the raw data from your webcam, for example, is compressed and formatted. H.264 is arguably the most popular codec for live streaming, and you can use it to create video files of up to 8K resolution. 

The important thing to remember is that, during the encoding, the various parameters that determine the quality and size of your video (such as compression, resolution and bitrate) are determined. That data is packed in a container, which is what holds the information about the structuring of the data and the file metadata, and at that point you have a video file. 

Why is video transcoding important to streamers? 

Broadcasting a stream solely at a high bitrate and resolution, without the option to downgrade the quality, might inadvertently prevent a sizable chunk of your audience from watching you. And that’s the problem transcoding solves. 

For example, you’re streaming live video to a network at its maximum recommended settings — a 1080p resolution at 60 frames per second with a bitrate of 6000 kbps. These are the highest recommended settings for Twitch. You never want to go over the maximum recommended settings because that can cause your stream to become unstable.

When the platform ingests your high-resolution, high-bitrate stream, it can transcode the stream to create an array of streams at different resolutions and bitrates. Then, the platform can use adaptive bitrate streaming to deliver the content that fits the viewers’ bandwidths the best.

On the viewers’ end, it would look like this: someone viewing your video on a desktop computer using a broadband connection with a high download speed would enjoy the full quality of your stream. If they have a temporary slowdown of their internet connection, the quality of the stream might be lowered to allow for an uninterrupted streaming experience.

At the same time, people can watch your stream on mobile devices at a lower resolution, with a lower bitrate and a significantly lower download speed requirement. Thanks to transcoding, you only have to make the one, original stream, and the platforms take care of the rest.

Do all platforms offer to transcode?

Even though it’s a very useful feature, transcoding isn’t supported by all platforms at all levels of access. This is one of the reasons behind the differing stream qualities on streaming platforms.  

Some platforms don’t offer much in terms of transcoding. These usually have rigid quality requirements that match the output on the platform. Other platforms, however, might offer some transcoding services.

Transcoding on Twitch

On Twitch, all streamers have access to transcoding as it’s available. Twitch Affiliates, however, get priority access to transcoding, while partners have full access to transcoding options. You can also freely choose to stream at lower bitrates and resolutions if you worry your audience might not be able to see you. Twitch is more flexible in that regard than other platforms.

Transcoding on YouTube

YouTube recommends you stream at a quality that ensures a stable live stream, and takes care of all the rest. That’s because it offers full transcoding of all streams. It will also give you the ability to use a variable bitrate for your stream, which is something Twitch doesn’t do.

Transcoding examples

Here are some ways transcoding is used:

• Changing a high-definition video file to a lower resolution
• Converting from a high-res editing format like Apple ProRes to a delivery format like H.264
• Converting a Windows Media File into an MP4 format so it can be played on another device
• Making videos uploaded to YouTube’s site available in multiple qualities and formats

Transcoding and streaming to multiple platforms

If you want to stream your video to multiple platforms at the same time, and use different quality settings for each one, you can use Restream for transcoding. Restream lets you push your live video to multiple platforms simultaneously and transcodes your stream to meet the requirement of the platform that offers lower-quality streams.

After you’ve purchased a certain amount of hours of transcoding from Restream, you’ll have the option to set it up to match the specific channels’ requirements.

FAQs