Within the videos that many of us watch on a weekly basis, there are many separate components that all play a part in letting the video run smoothly. Many of us have heard of terms such as bitrate, codec, avi, etc, but not many people actually know what these terms mean. The fragmented nature of video files is one of the many reasons why video advertising sees so many more errors than display advertising, where only a simple image file needs to bee displayed. Today’s article will break down the many different components of a video file and how each plays a part rendering the video to the user.
Aspect Ratio
An aspect ratio is the relation ship between a video’s length and width in a ratio format. For example, a video that is 1000×500 has an aspect ratio of 2:1. The most common video aspect ratios today are 4:3 (fullscreen) and 16:9 (widescreen). Films in the 1970s used 4:3 aspect ratios as that was the aspect ratio of the films that they were shot on. These days, the majority of video files use the 16:9 aspect ratio to accommodate the modern tv screen.
Dimensions
The majority of video files today use video dimensions in multiples of 16. As an example, let’s look at the Youtube video sizes that we are all familiar with. Youtube videos use the 16×9 aspect ratio.
- 2160p: 3840×2160, 4K HD
- 1440p: 2560×1440 HD
- 1080p: 1920×1080 HD
- 720p: 1280×720 HD
- 480p: 854×480 Standard Definition
- 360p: 640×360 Standard Definition
- 240p: 426×240 Standard Definition
- 144p: 256×144 Standard Definition
Bit Rate
A video’s bit rate measures how much data a video contains, measured in megabits per second (mbps). In general, there is a linear relationship between bit rate and video quality. Higher quality resolutions such as 4K HD tend to have higher bit rates. In addition, more compressed video files will take up less space on a hard drive but have lower video quality. With high quality videos, households with weak internet connections will see constant buffering to allow for the video to play.
Frame Rate
A frame rate is exactly like it sounds. It is the number of frames that appear on the screen per second. With a frame rate of 60fps, there would be 60 images or “snapshots” shown per second. Videos with smaller frame rates are a source of those choppy images that we’ve all come across. (Note that this is different from the bit rate lag. Bit rate lag actually shows the user a smooth picture when it is playing, but buffer from time to time. Frame rate lag will constantly show the picture without buffering stops, but lag constantly).
File Size
The amount of space that the video file would take on a hard drive. This can be calculated by bit rate * duration.
Duration
This is simply the duration of the video.
File Format
File formats are the containers that hold the video files. These containers include everything from video codecs, audio codecs, and data. It’s important to note that many file formats and codecs can be mixed and matched.
A comprehensive pictograph on file formats by uscreen.tv can be found below.
Codec
This is the compression and decompression method used to compress a particular video file. The primary purpose of a codec is to pack up video files to save space and unpack them while a user watches the video. Because of poor codec quality and compatibility issues with the different file formats, it is not uncommon for users to experience playback errors when using different codecs.
Example video codecs:
- FFmpeg
- Xvid
- DivX
- H.264
- H.263
- MPEG-4
- MPEG-2
Audio
It’s important to note the audio files are actually separate from video files. However, they are held in the same file containers. The audio codec will have to work in conjunction with the video codec to display a video file. Sometimes, an audio codec may malfunction while the video codec works, resulting in a video without sound.
Example audio codecs:
- WAV
- AIFF
- MP3
- AAC
- WMA
- Opus
Sources
- https://support.brightcove.com/optimal-video-dimensionshttps://support.brightcove.com/optimal-video-dimensions
- https://www.jbistudios.com/blog/video-translation-101-frame-size-aspect-ratio
- https://www.techwalla.com/articles/video-bitrate-vs-frame-ratehttps://www.techwalla.com/articles/video-bitrate-vs-frame-rate
- https://www.any-video-converter.com/mac-tutorial/video-codec.php
- https://www.uscreen.tv/blog/the-quest-for-the-best-video-format-how-do-you-know-whats-best-for-you/
- https://www.dacast.com/blog/best-audio-codec/
It’s unwise to pay too much, but it’s worse to pay too little. When
you pay too much, you lose a little money – that’s all. When you pay
too little, you sometimes lose everything, because the thing you
bought was incapable of doing the thing it was bought to do. The
common law of business balance prohibits paying a little and getting a
lot – it can’t be done. If you deal with the lowest bidder, it is well
to add something for the risk you run, and if you do that you will
have enough to pay for something better.— John Ruskin
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