Video size is often illusive and random to most people. Large, long HD films may only be several hundred MB, while a quick, daily-shot video from your phone could also be several hundred MB. This unpredictability is compounded by the common belief that reducing video size inevitably lowers the quality, which can make things even more confusing.
In this article, I’ll explain what’s behind the video size myth and help you understand how large a video should be, giving you more clarity the right size for your HD 5 minute video.
What is a Video and What is Video Compression?
A video is essentially a sequence of images, often referred to as frames, that are displayed rapidly in succession to create the illusion of motion. Depending on the video’s frame rate (fps), these images are shown at a rate of 30 frames per second (fps) or higher. This means that for every second of video, there are 30 individual images playing in quick succession.
Now, imagine trying to store all of these frames in their raw form. Let’s break it down with a simple example:
| One 1080p Image | One Second of 1080p Video ( 30 fps ) | One Minute of 1080p Video ( 60 seconds ) |
| 1MB | 30MB | 1,800MB ( 1.8GB) |
Clearly, storing video in this raw format would be incredibly inefficient and take up a huge amount of storage space. Fortunately, there’s a more efficient way to store video: compression.
Video Compression
The key to making videos smaller lies in recognizing the similarities between consecutive frames. In most cases, the images from one frame to the next are very similar. For example, if you’re watching a video of someone walking, their body position will be slightly different from one frame to the next, but the background and most of the image will remain the same.
To capitalize on this, video compression techniques store only the differences between consecutive frames rather than storing each frame in full. In simple terms, only one full image among few seconds is saved, and the following frames only store the changes or differences from those full images. This technique is known as video compression.
What are the Factors that Affect the Video Size
Video Codec
While the concept of video compression sounds simple, the real challenge lies in identifying these similarities. This task is the job of video engineers who design compression algorithms, which is what we know as video codecs. These are the algorithms that figure out how to compress the video by detecting similarities between frames. Common codecs include H.264, HEVC (H.265), VP8, and VP9.
When you watch or upload a video, these codecs are typically packed into formats like MP4. Most of the time, you don’t need to worry about which codec is being used. However, newer codecs tend to offer better compression ratios. For example, HEVC (which is newer than H.264) can compress video more efficiently while preserving higher quality.
Video Content and Scene Complexity
Aside from the algorithm used, the content of the video itself plays a huge role in determining its file size. Here’s why:
• Still Images / Low Motion: In videos where very little is moving (like a still image with minimal changes between frames), the compression algorithm can achieve a very high compression ratio. This allows it to reduce the file size significantly without losing much quality.
• Rapid Movement / Complex Scenes: On the flip side, videos with rapid movement or complex scenes (like sports footage) present a challenge for compression. Since the frames differ greatly from one another, it’s harder for the algorithm to find similarities between them. As a result, the compression ratio will be lower. Further attempts to compress the video may reduce the image quality significantly.
Why Are iPhone Videos So Large?
If you’ve ever wondered why videos shot on your phone end up being so large? The answer lies in how your mobile device handles video encoding. Unlike professional video encoding softwares on computers, most smartphones (including iPhones) use hardware encoding that compress video at a constant bitrate. This means that, regardless of how much or little movement is in the video, the device applies a consistent level of compression across the entire video.
Hardware encoding doesn’t take full advantage of analyzing similarities between frames. It is designed because mobile devices usually lack the computational power to do such in-depth analysis on the fly. Consequently, videos from mobile devices may be larger than expected, and re-encoding or compressing the video later can often yield a much better file size with minimal quality loss. Read more about our blog upon how to compress a video on iPhone.
How Large a 5-Minute HD Video Should Be?
The truth is, the size of a 5-minute HD video can vary greatly. As much as it might sound unhelpful, the answer really is it depends. The file size is influenced by a number of factors:
1. The Video Codec: Different codecs offer different levels of compression. For example, HEVC (H.265) will compress the video more efficiently than H.264, which means you can expect a smaller file size with similar quality.
2. Motion and Similarity Between Frames: Videos with a lot of movement or changes from frame to frame will have a larger file size, as the compression algorithm will have a harder time finding similarities to reduce the data. On the other hand, static scenes with minimal movement will compress more effectively and yield a smaller file size.
3. Compression Methods: Not all compression methods are equal. If you don’t use the most efficient compression method for your video, you might end up with a file that’s much larger than it needs to be.
In that sense, some platforms provide general guidelines for video sizes:
| Netflix | Youtube | |
| Bitrate Suggests | 5Mbps-7Mbps | 8Mbps-12Mbps |
| HD 5min Video Size Based on Bitrate | ~225MB | ~375MB |
| Reference | Link | Link |
However, these guidelines don’t necessarily apply to your specific video. Your video’s content, motion, and codec choice will all affect the final file size.
Redpandacompress’s Automated Compression
To make things easier, Redpandacompress provides an automated compression tool that analyzes your video specifically and determines the most suitable compression settings. This ensures that you get the best possible size without compromising on quality. If you’re wondering how large your 5-minute HD video should be, give it a try here: Redpandacompress.com.
Fei is a skilled software engineer. He previously worked at Google and now at a startup. His expertise includes web media processing, cloud architecture, complex algorithms, and AI training and deployment. Beyond work, Fei enjoys diving into new knowledge and is a big fan of strategy games.