The video experts blog
Video Transcoding: The Best Video Bitrates for Mobile Streaming [2022 Update]
The ways in which users access online video content from mobile devices have evolved in recent years. When the first iPhone came out, mobile streaming wasn’t possible due to incompatible video players. Even after this issue was resolved by the creation of HTML5 video players, mobile internet speeds continued to pose challenges.
Transcoding is a technique that’s helped broadcasters overcome these challenges by allowing them to stream multiple copies of their videos in sizes that are suitable for different internet connections. It can be tricky to figure out the best video resolution for mobile devices.
When considering transcoding services, it’s important to get the settings just right. Incorrect settings can translate into a poor-quality or even unwatchable video. Because many people today use so many different devices, proper settings are even more essential than just ensuring the acceptable video quality. It takes a little effort to ensure you are providing your viewers with the best video format for mobile phones.
In this post, we’re going to talk about video transcoding and how to choose the best bitrate settings for mobile phone viewers. We’ll start by digging deeper into the challenges posed by mobile devices before we get into the technical aspects of transcoding and video bitrate. From there, we will discuss some specific bitrate settings that broadcasters can use for reaching a mobile audience.
You’ll have a good understanding of how to select and provide the best video resolution for mobile devices by the end of this article. Surprisingly enough, this is a pretty simple process.
Table of Contents
- Streaming to Mobile Viewers
- What is Transcoding?
- What is Video Bitrate?
- Best Bitrate Settings for Mobile Phone Viewers
- What is Multi-Bitrate Streaming?
Streaming to Mobile Viewers
Over the past decade, smartphones and tablets have become increasingly popular. Mobile devices have given people access to endless amounts of information and media at the tap of a screen. The size and efficiency of these devices have changed the ways of the world, and have provided unprecedented convenience.
When smartphones first rose to popularity, the technology was not suitable for streaming video content. The standard video player, Adobe Flash player, was not compatible with mobile devices. Leaders in the online streaming community realized that by not serving mobile users, broadcasters would miss out on large potential audiences. This was great foresight, as more people access the internet now through mobile devices than traditional desktops.
That’s where the HTML5 video player and HLS delivery came into play. These technological updates made it possible to stream on just about any internet-enabled device.
However, challenges related to internet speed continued to prevail. Cellular data and WiFi connections weren’t nearly as strong or capable as Ethernet connections, but unfortunately, those are the only options for mobile devices. Without the support of a fast and reliable internet connection, viewers are subject to buffering and lagging, which detract from the viewing experience.
Today, WiFi and cellular data connections are stronger than ever. In most situations, they’re capable of streaming online video content, but there are still situations where the connection is less than ideal. This is mostly the case when streaming with cellular data.
Fortunately, there are techniques that broadcasters can use to bypass the current internet limitation of users to ensure the best quality streaming for all of their viewers.
What is Transcoding?
Video transcoding is the process of creating multiple renditions, or copies, of a video with different technical specifications. Video files are often bulky, so transcoding them makes it possible to stream them with different streaming setups.
For example, you may wish to reduce file sizes further or change the resolution of the video. It may also be necessary to use an alternate format to reach users on a specific device or operating system. That is what video transcoding helps you with.
In order to better understand transcoding, it’s important to have a clear understanding of video compression.
The natural format of a video is “uncompressed.” This means that each frame of the video is recorded as a standalone image. 30 frames per second is standard. However, uncompressed video often results in huge file sizes that are impractical for streaming over the internet.
As a result, most video cameras actually record compressed formats. This means that some data is thrown out to reduce file sizes. Compression is achieved through a variety of very clever methods, but the basics are easy to understand.
Let’s say the whole frame of your video is black for two seconds, for example, a subject could be entering a dark room. An uncompressed video might store all 60 frames as individual images.
Compression enables you to save space by instead saying “render all pixels black for the next 60 frames.” In practice, this can often cause some loss of quality.
There are a variety of different compression schemes used for reducing the file size of the video and then uncompressing it for playback. A major way in which these different compression schemes are implemented is in the form of the video codec.
A video codec, the name of which is a portmanteau for “coder/decoder,” is a for of media technology that’s used for encoding and decoding video files. Codecs are available in both hardware and software forms, but codec software is a little bit more relevant to video streaming since transcoding is such an important step in it. Transcoding requires a pretty thorough understanding of codec parameters and how they’re managed by software.
Currently, one of the most common codecs in livestreaming is H.264. It’s the most popular because it’s efficient and supported on almost every mobile device.
H.264 will likely eventually be replaced by H.265 and VVC. These two codecs are both updates to H.264 but are limited by the fact that they’re not yet widely adopted.
What is Video Bitrate?
Video bitrate is the amount of data being transferred between a source and destination during a given time. Bitrate and streaming settings can be manipulated at the encoder level to produce different qualities of video, such as Standard Definition or High Definition.
Bitrate is measured in bits per second or bps. Video bitrate, in particular, is measured in megabits per second (Mbps).
Best Bitrate Settings for Mobile Phone Viewers
Mobile device users have a few unique requirements. For one, data is precious. Although a lot of mobile users have unlimited data plans these days, even the most robust plans have their data limitations. For example, users on an unlimited plan may see a decrease in speed for every 30 GB that they use.
Furthermore, web connections in mobile environments can vary dramatically over short periods of time, so the streaming video has to be properly transcoded for the mobile environment. Due to this, optimizing file sizes for mobile video is essential. This involves reducing the bitrate, or the amount of data transferred per second in a streaming file.
At the same time, processing power and screen quality on mobile are advancing. Retina and Ultra-HD (4K) screens are becoming common on smartphones. Poor video quality is especially apparent on screens of this quality. Screen size is increasing too. The norm for smartphone screen sizes these days is around five inches. With these larger screens, a video that is too compressed or too small delivers a subpar viewing experience since flaws and artifacts become more magnified.
Fortunately for viewers (but unfortunately for broadcasters), there is a wide range of mobile devices on the market. It’s great for choice, but it also means that older devices don’t support the newer formats and file sizes that work best on more modern phones and tablets. With that said, here are our recommendations for a few different categories of users.
To reach every device, including older ones:
- Video bitrate: 400 kbps or less
- Frame size: 320 x 240
- Frame rate: 30 fps
- Audio bitrate: 64 kbps or less
These settings can reach just about every mobile device around, including old iPods, Blackberries, and more.
To reach almost every device, but deliver better quality:
- Video bitrate: 1100 kbps or less
- Frame size: 480 x 270 pixels (very low-end devices) or 640 x 360 pixels (plays better on iPhone 4G and Android phones)
- Frame rate: 30 fps
- Audio bitrate: 128 kbps or less
This should reach nearly every smartphone and tablet, but is too small for more modern phones.
To reach higher-end smartphones:
- Video bitrate: 3500 kbps (WiFi), 2000 kbps (cellular) or less
- Frame size: 1280 x 720 or 960 x 640
- Frame rate: 30 fps
- Audio bitrate: 160 kbps or less
These settings will typically work really well for most modern smartphones and tablets.
H.264 Profile Settings
Of course, choosing the right video bitrate for mobile isn’t the only thing to consider. That’s why we included frame size, frame rate, and audio bitrate information here. However, another important consideration is the H.264 profile you use.
An H.264 profile is a set of parameters that define the capabilities of the encoder. These parameters include the maximum number of reference frames, which can be used to predict other frames. Those frames, along with other parameters, determine the quality of the output stream.
In general, we recommend the “baseline” profile for all mobile devices. It ensures backward compatibility and delivers good quality with minimal delay.
What is Multi-Bitrate Streaming?
Multi-bitrate streaming allows broadcasters to stream multiple renditions of a video at the same time and gives viewers access to a video with a bitrate that makes sense with their internet speed. An adaptive bitrate video player determines the best bitrate for each individual viewer and automatically pushes the optimal rendition. It is the best way to achieve the best video resolution for mobile devices for all of your viewers.
These techniques allow broadcasters to simultaneously stream to users with fast and slow internet connections without sacrificing the quality of experience for either. Users with faster internet can watch crystal clear high-resolution content, while users with slower internet can watch lower-resolution content without lagging or buffering. This helps ensure the best video format for mobile phones and tablets.
Bitrate Settings for Different Resolutions
As we discussed earlier, different bitrate settings yield different picture quality. Here are the bitrate combinations for the most common video resolutions.
|Name||Ultra-Low Definition||Low Definition||Standard Definition||High Definition||Full High Definition|
|Video Bitrate (kbps)||350||350 – 800||800 – 1200||1200 – 1900||1900 – 4500|
|Resolution Width (px)||426||640||854||1280||1920|
|Resolution Height (px)||240||360||480||720||1080|
The “main” profile contains the baseline parameters for h.264 encoding, while the higher profiles add significantly to the codec. Put simply, higher profiles support higher quality, while the main profiles emphasize speed and efficiency.
Delivering video to mobile devices is increasingly common, but it requires high quality coupled with manageable file sizes. The settings we’ve discussed here should help you deliver excellent video to your viewers.
As you choose an online video platform (OVP) for hosting your streams, you should look out for transcoding support. Luckily, most well-rounded OVPs should include video transcoding tools in their offerings. These tools are essential to make multiple versions of each video file you host.
You should also look out for adaptive bitrate streaming support. That way, viewers can automatically be sent the version of the video that works best for them.
Dacast offers support for these and other professional broadcasting tools. Try our live streaming platform risk-free for 14 days and test all of our features for yourself. Sign up today to start streaming for free.
For exclusive offers and regular live streaming tips, you can also join our LinkedIn group. This group offers a professional environment to network with industry insiders and connect with streaming professionals.