What are the Main Factors that Determine Video File Size

Have you ever wondered why the file size of some videos are much bigger than others? It can help to know exactly what factors determine video file size, and in some cases it may even allow you to reduce the size of some of yours.

The main factors that you need to know about that have a part to play in the video file size are:

  • Duration

As you can imagine longer videos tend to have larger file sizes, simply because there is more data in the video file. Although it may seem like the most important factor, it is actually just one of several however – but it does interrelate with the rest.

  • Video Bitrate

The video bitrate is the amount of data that the video utilizes per second. It is measured in bits per second, and it directly affects the video file size – which is essentially the video bitrate multiplied by its duration.

Different videos require different bitrates to be displayed without a loss of quality. The factors that affect the required bitrate are the resolution, frame rate, and video codec that is used to encode the video.

If the bitrate is not high enough, the quality of the video will suffer and compression artifacts may show up during playback.

  • Video Codec

As mentioned the video codec plays a role in determining the bitrate that is required. However, it is a bit more involved than that, as the video codec is what is used to compress the video data.

The codec will determine how efficiently the video data can be compressed. Some codecs can provide better compression ratios than others, and for example, the H.265 codec has up to a 50% better compression ratio than the H.264 codec.

The compression ratio for any given codec can differ depending on the content of the video.

That should cover the main factors that affect the video file size. As you can see they are very interrelated, and there are lots of other factors such as the resolution, and frame rate that play a role as well.

On top of that, it should be noted that video files may also contain other types of data such as the audio codec and audio data, and data for captions, menus, chapters, and so on. In most cases, this contributes a minimal amount to the overall file size of the video, however.

Based on these factors you should see how converting the video can help to compress it. If you want to see a way that can be done, you can refer to this guide on how to convert MP4 to AVI.

In fact you’ve probably realize that there are other ways to reduce the video file size, such as by lowering the bitrate or trimming the video itself. At the end of the day you should assess each video individually and determine the best way to reduce its file size – if that’s what your goal is.

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