api.video lets you quickly and securely deliver on-demand and live-stream videos directly from your website, software, or app. 

api.video

Glossary-Bitrate.svg

## What is video bitrate? 
The bitrate of a file is measured by the number of bits being transmitted over a period of time. For video it is typically measured in kilobytes per second (kbps) or megabytes per second (mbps).  

The bitrate of a video is most influenced by the size and quality of the video being transmitted. As an example a 4K video (3840 x 2160) has over 8 times as many pixels per frame than a HD video (1280x720) (8.2M pixels vs 921kpixels), and will therefore have a higher bitrate (assuming similar compression settings for both videos). (See table below for the bitrates delivered by api,video.)

Different compression [codecs](https://api.video/what-is/codec/) have a large effect on bitrate. As video compression algorithms improve, videos can be compressed more and more at the same quality, lowering the bitrate of the video.  As an example VP9 files are ~50% smaller than VP8, and AV1 files are [30% smaller](https://engineering.fb.com/2018/04/10/video-engineering/av1-beats-x264-and-libvpx-vp9-in-practical-use-case/#:~:text=Our%20testing%20shows%20AV1%20surpasses,however%2C%20due%20to%20increased%20complexity.) than VP9 For this reason, new codecs are under constant development.

If a video's bitrate exceeds the throughput of the network, the video will stall - it will playback faster than it can be downloaded.

## Adaptive Bitrate Streaming (ABS)

ABS is the ability of the video player to identify the display size, and the network capability of the device - and request a version of the video that will play for the end user.

## Bitrate at api.video

At api.video, all uploaded videos are converted into Adaptive Bitrate Streams. currently, our streams are encoded as follows:

|Resolution    |    FPS    |   Video Bitrate    |    Audio Bitrate    |
|---|---|---|---|
|240p|18|250 KBPS|96 KBPS|
|360p|25|800 KBPS|128 KBPS|
|480p|25|1400 KBPS|128 KBPS|
|720p|25|2600 KBPS|128 KBPS|
|1080p|30|4400 KBPS|128 KBPS|
|2160p (4k)|60|16000 KBPS|128 KBPS|  

&nbsp;  

This ensures that even on the slowest network connections, video can be played.  Typically video players will pick a video bitrate that matches the screen size or 80% of the available network speed.


Glossary-Bit-Rate-Control.svg

## What is Bit Rate Control?

Bit rate control is a crucial aspect of video encoding and compression, allowing content creators and video professionals to manage the quality, file size, and streaming performance of their video content. By carefully controlling the bit rate, users can strike a balance between visual quality and file size, ensuring their videos are optimized for various delivery scenarios and playback devices. 

## Understanding Bit Rate Control

The bit rate of a video file refers to the amount of data (in bits) that is processed or transmitted per unit of time, typically measured in kilobits per second (kbps) or megabits per second (Mbps). Higher bit rates generally result in better visual quality but larger file sizes, while lower bit rates can lead to reduced quality but smaller file sizes.

Bit rate control strategies allow video creators to manage this trade-off effectively. The two primary bit rate control methods are:
1. **Constant Bit Rate (CBR)**: In this approach, the bit rate remains consistent throughout the entire video, maintaining a fixed data rate. CBR is useful for ensuring a predictable and stable video stream, but it may result in quality fluctuations.
2. **Variable Bit Rate (VBR)**: VBR dynamically adjusts the bit rate based on the complexity of the video content, allocating more bits to scenes with more detail and movement, and fewer bits to simpler, less demanding scenes. This can lead to better overall quality and more efficient file sizes.

## Factors Influencing Bit Rate Selection
When choosing the appropriate bit rate for a video, several factors should be considered:
1. **Resolution and Frame Rate**: Higher resolutions and faster frame rates generally require higher bit rates to maintain visual quality.
2. **Content Complexity**: Videos with more movement, detail, and dynamic scenes typically require higher bit rates to avoid quality degradation.
3. **Delivery Platform**: The target platform or distribution channel, such as online streaming, broadcast television, or physical media, may have specific bit rate requirements or limitations.
4. **Bandwidth and Device Capabilities**: The available network bandwidth and the playback capabilities of the target devices can influence the optimal bit rate selection.

## Optimizing Bit Rate for Video Delivery
Striking the right balance between bit rate, quality, and file size is crucial for delivering high-quality video content efficiently. This may involve experimentation, testing, and adjusting the bit rate settings based on the specific requirements of the project, the target audience, and the delivery ecosystem.

Effective bit rate control can significantly enhance the user experience by ensuring smooth playback, minimal buffering, and the preservation of visual fidelity, making it a fundamental consideration in video production and distribution.  

&nbsp;  

At api.video, we understand the importance of bit rate optimization in delivering high-quality video content. Our platform provides robust tools and features to help you manage the bit rate of your videos, ensuring they are optimized for seamless playback across a wide range of devices and platforms. Whether you prefer the consistency of Constant Bit Rate or the adaptive nature of Variable Bit Rate, api.video empowers you to find the right balance between file size and visual quality, delivering an exceptional viewing experience for your audience. [Sign up now](https://dashboard.api.video/register)!

Glossary-buffer-buffering.svg

## What is buffering in video playback? 

**Buffering** is the state where video playback stops because there is no video available locally on the device. This state is typically reached when a video has partially downloaded, but playback has reached the end of the downloaded video. With no more video to play, there is nothing for the player to do, other than stop the video.  Often a spinner (or other symbol indicating 'please wait') is displayed. A common synonym for buffering is stalling.

**Buffer**: A video buffer is the amount of video that is downloaded and available on the device for playback. This is video that is ahead of the current playback mark.

small_how-to-stop-buffering-when-live-streaming-620x315.jpeg

thumbnail_how-to-stop-buffering-when-live-streaming-620x315.jpeg

how-to-stop-buffering-when-live-streaming-620x315.jpeg

In many video players, you can see the buffer as a differently colored line. Usually, you can see how many seconds of the video have been played, but also the amount of video seconds in the buffer. And of course, thow much of the video has not yet been downloaded.

In [HLS](https://api.video/what-is/http-live-streaming-hls/) video streaming, it is common for the player to have 2 segments of video in the buffer before video playback can begin.

The goal of adaptive bitrate streaming is to ensure there is enough video in the buffer by changing the video quality to adapt to the network speed. When the network slows down, the player begins requesting a lower quality video (smaller in size so will download faster). This prevents the video buffer from emptying - which leads to a stall or buffering state of the video. 

Glossary-Bumper.svg

## What is a video bumper?

Just like cars have a front and rear bumper, videos can have short intro and exit clips that denote the beginning and end of a video.

Bumpers are usually short (under 10 seconds, but typically around 5 seconds long) that describe the brand and the topic of the video that is being presented. They help set the stage for the content, so the viewer knows what to expect when watching your video.

## The video welcome (intro) bumper

The Introduction bumper will be the first thing your viewers see when your video starts playing. Typically, there is text describing the content of the video, with perhaps a company icon, and maybe the name of the person presenting during the video. This allows you to catch the viewer's attention, and reinforce brand awareness for your company.  It also helps make your videos look polished, as clearly there was editing done to create and add the bumpers.

The following bumper:

intro-bumper-example.jpg

* api.video logo at the top center, and asks viewers to "start building with api.video." This reinforces that the viewer will learn from api.video while watching.
* Title: a.video demos. api.video hosts all of its demo applications at a.video, so this video is describing a demo hosted at this domain.
* Second title: bumper.a.video. The demo app to be discussed is bumper.a.video 

Seeing this information allows the viewer to understand what the video will be about.

## The video exit (outro) bumper

At the end of the video, it is often desirable to give your viewers a call to action on what they can do next with the knowledge gained during the video.

In the case of the video above, we want to thank our viewers for watching, but also remind them that they can try out the demo at [bumper.a.video](https://bumper.a.video)

So we created the following image:

outro-bumper-example.jpg

We thank the user for watching, and suggest that they try out our application to add bumpers to a video.



## What are captions?
Captions are the transcription of spoken dialog into written text that is displayed during video playback.  Captions can also describe actions that occur in the video.  Subtitles are similar, but are often a translation of the captions into a different language, and do not contain the descriptions. While initially introduced as an accessibility feature for those who are deaf or hard of hearing, captions are increasingly popular for video playback.  Amongst the reasons:

1. Autoplaying video on the web must be muted. By adding captions, users tend to linger on the autoplaying video.
2. Videos can be watched at a lower volume - allowing parents to watch videos while children sleep (or the other way around).
3. Accents. Sometimes, the audio can be hard to understand, and the captions help resolve this issue.

## Types of captions
You might think that captions are all the same, but there are multiple types. Let's go over some of the most common ones:

* **Closed Captions** (CC) - CCs are a transcription or translation of the dialogue and other audio information when sound is unavailable or not clearly audible. 
* **Open Captions** - These are like closed captions except you can't toggle them on and off as you can with CCs, they're there the whole time.
* **Subtitles** - While these are basically the same thing as CCs, HTML5 gives them a slightly different definition. Subtitles are transcriptions or translations of dialogue when sound is available but not understood by the viewer. For example, if something is spoken in a foreign language.
* **Subtitles for the Deaf and Hard of Hearing (SDH)** - These subtitles can contain extra information about the audio that the deaf might not be able to understand. For example if a song is playing, or there are special sound effects in the scene. 

## How are captions stored? 
In the old days, for analog TV, captions were hidden on the 21st line of the vertical blanking interval (VBI) of a video signal. (A VBI is the time between the end of the final visible line of one frame of video and the next one. It's specific to analog TVs.) To see the invisible line, you'd 'decode' when viewing using the TV remote. 

Today, digital video displays are still designed to handle the analog style of captions, which is called CEA-608. CEA stands for Consumer Electronics Association. However, the new style of captions, called CEA-708 or sometimes EIA-708 (Electronic Industries Alliance) captions are now preferred. This is because CEA-708 captions let you have multiple text sizes, 64 text colors, 64 background colors and 8 different font options. You can also change the opacity of the background and dropshadow your text (although I'm not sure why captions need dropshadowing). Additionally, CEA-708 captions support special characters and symbols, allow multilingual capability and they don't have to be positioned on line 21, instead they're embedded in the video stream. 

## Caption delivery: the VTT file

The Video Text Track (VTT is a standardized file type to deliver captions.

For each caption, the VTT file identifies a start and end time for each string of text. For example, if you were Rick Rolled, you might see this caption:

```
5
00:00:44.030 --> 00:00:47.260
Never going to let you down.
```


## Captions with api.video

Captions are added to a video using the [Upload caption](https://docs.api.video/reference#post_videos-videoid-captions-language) endpoint.  

The captions can appear by default by adding #show-subtitles to the [player URL](https://docs.api.video/delivery/video-playback-features), or using the showSubtitles option with the [player SDK](https://docs.api.video/sdks/player/apivideo-player-sdk).

You can read more in our [tutorial](https://api.video/blog/tutorials/how-to-add-captions-to-your-videos/)


Glossary-Bit-depth.svg

## What is bit depth?

Bit depth describes the level of detail for the color information stored in an image. The higher the bit depth an image has, the more colors it can store. The more colors that can be stored, the smoother and more accurate an image looks. The lower the bit depth is for an image, the more likely you are to see sharp delineations between color changes in the images. Sharp changes that don't look like an image in real life are referred to as banding. 

An image depicting the difference between 24-bit and 8-bit color 

bit-depth.png

In the image presented above you can see how increased bit depth (the image on the left) yields a smoother image, while less bit depth results in what is known as banding - where you can see separate bands of color instead of a smooth blend between the colors. With techniques like [dithering](https://api.video/what-is/dithering/), you can conceal banding with varying degrees of success and avoid going up to a higher and more data expensive quality level. It depends on the image, the technique you use, and how high quality you need the final output to be. 

When discussing bit depth, you'll hear things like this codec or color space is 8-bit, or this is 10-bit, 16-bit or similar. If someone says this is 8-bit color, what they're saying is that there are 2^8 possible values for red, green and blue in the image. That means you can have up to 256 values per color. How many values are possible changes rapidly as you increase bit depth. For example 10-bit appears to be a slight increase from 8-bit until you realize that this is a way of saying there are 2^10 possible values (or 1024 values) per color (red, green, blue). It's a big quality increase, and therefore requires a lot more storage. 

As you can see, high quality color can become expensive quickly. So it's important to determine the level of quality you need. For example, you want the highest bit depth possible when you're capturing video footage because this gives you the most choices later when you process it. You can always drop information to create images with lower bit depth, but you can't add color information that you don't have. 

## What is the autoplay attribute in HTML5? 
Autoplay is an attribute commonly used in the HTML5 video tag. It tells the browser that the developers would like the video to play automatically when the webpage loads.

The actual implementation of autoplay is not as straightforward. We'll walk through the options in order of ease of implementation:

## General autoplay settings

* On mobile Chrome and Safari (and in most other browsers), videos will only autoplay when paired with the [muted](https://api.video/what-is/muted/) attribute. Of course, without audio, you might want to consider adding [captions](https://api.video/what-is/captions/) to your video.

* If a user has interacted with video on your website in the past, videos with autoplay set will play automatically with audio.  Each browser has different criteria to make this occur.  This is can hard to test, since once you interact with the page - you'll see the video autoplay.

## api.video autoplay settings

* api.video player: You can set the ['force autoplay'](https://docs.api.video/reference#patch_players-playerid) attribute to true, and all videos viewed with this player will autoplay (they will be muted).  

* Player SDK: Setting the autoplay attribute will result in the video playing as soon ias it is loaded.

```
   player.loadConfig({
      id: "<VIDEO_ID>",
      id: "<VIDEO_ID>",
      autoplay: true,
      hideControls: true,
   });
```

* api.video video: You can set the player to autoplay in the url by adding #autoplay to the end of the player url.

small_bit-depth.png

thumbnail_bit-depth.png

Glossary-Autoplay.svg

Glossary-Aspect-ratio.svg

## What is aspect ratio?
Aspect ratio refers to the ratio of the width and height dimensions of a video. You can calculate the ratio by dividing the width and height by the greatest common divisor of both.

For a video that is 1920 pixels wide and 1080 pixels in height, the greatest common divisor is 120, resulting in an aspect ratio of 16:9.

The two most common aspect ratios for video are 4:3 (e.g. 640x480) and 16:9 (1920x1080 or 1080p). With vertical video, popular for mobile device recording, the common aspect ratio numbers get reversed and 16:9 becomes 9:16.

The square aspect ratio, 1:1, is also becoming popular because of social sites like Instagram that allow square video as an option.

## What is the history of the aspect ratio?
When film was first starting out, everything was shot in 4:3. This was the standard for motion pictures, so it was easy to create everything like this. However eventually, people began experimenting with different aspect ratios, especially wider ones, which could help to create a more immersive experience for film goers. As it turns out, wider aspect ratios do a better job of mimicing how we see the world around us. To be able to stretch films wider and wider, film creators originally used anamorphic lenses. These lenses distorted captured images vertically, allowing them to be stretched out later and look 'right' on wide screens. These lenses are still used today. 

## What are the most popular aspect ratios?
The most commonly used aspect ratios today are: 
- 4:3 - It's what film started out on, but today it's more likely to be used for television and computer screens.
- 16:9 - Most cameras shoot with this aspect ratio, but this is more likely to be used for TV than any other medium. 
- 1.85:1 - This is slightly wider and shorter in height than 16:9. It's used for television, but it's used for TV shows that are going for a more cinematic look-- thus the slight additional width and smaller height. There is a slight letterbox (band of black at top and bottom of video) on video shot in this aspect ratio.
- 2.35:1 and 2.39:1 - These are used for films that are going to appear on the big screen. These aspect ratios always give a more immersive, filmlike quality to whatever's being shot. They're great for the cinema, but because they result in a bigger letterbox, people don't like this aspect ratio as often if they're watching something on TV.

## Why do aspect ratios matter? 
Aspect ratios evoke different kinds of feelings in viewers. Even an untrained viewer will feel different when they see a really wide, cinematic shot vs. a smaller, narrower television type shot. The wider aspect ratio can be used to create more dramatic landscapes while narrower shots can be used to give a more everyday feel. The psychological effects of aspect ratio on a story's theme, narrative and dramatic tension is a popular topic of debate. 

## Aspect ratio and api.video
At api.video, because content is transcoded to [HLS](https://api.video/what-is/http-live-streaming-hls/) so that it can easily be streamed across the web, the aspect ratio by default is 16:9. 

## What is an Artificial Intelligence?

Artificial Intelligence (AI) refers to the simulation of human intelligence in machines programmed to think and learn like humans. In the context of video technology, AI encompasses a wide range of techniques and applications that enable computers to perform tasks that typically require human intelligence, such as visual perception, speech recognition and language translation.

## AI Technologies in Video Processing
AI in video processing relies on several key technologies:
1. Computer Vision: For analyzing and understanding visual content
2. Speech Recognition: To transcribe and understand spoken words in videos
3. [Natural Language Processing](https://api.video/what-is/natural-language-processing/): For understanding and generating human language
4. [Machine Learning](https://api.video/what-is/machine-learning/): To improve performance through experience
5. [Neural Networks](https://api.video/what-is/neural-networks/): For complex pattern recognition and decision-making  

&nbsp;  

These technologies work together to enable sophisticated video analysis, editing, and generation capabilities.

## Applications of AI in Video Technology
Artificial Intelligence has revolutionized various aspects of video technology. In content analysis, AI can automatically categorize, tag, and describe video content, making it easier to search and organize large video libraries. For editing, AI-powered tools can suggest cuts, transitions, and even create rough cuts based on content and style preferences. In visual effects and enhancement, AI algorithms can upscale video resolution, reduce noise, and even generate complex visual effects.

AI also enables personalized content delivery by analyzing viewer preferences and behavior to recommend relevant videos and create tailored viewing experiences. Moreover, advanced AI models, particularly [Generative AI](https://api.video/what-is/generative-ai/) systems, can create entirely new video content from textual descriptions or combine elements from existing videos in novel ways.

## Challenges and Ethical Considerations

While AI offers tremendous potential in video technology, it also presents significant challenges.
- Bias and Fairness: AI systems can perpetuate or amplify biases present in their training data, potentially leading to unfair or discriminatory outcomes.
- Privacy Concerns: The ability of AI to analyze and understand video content raises questions about surveillance and personal privacy.
- Creative Control: As AI becomes more involved in content creation, there are concerns about maintaining human creativity and authorship.
- Transparency: Many AI systems, especially deep learning models, operate as "black boxes," making it difficult to understand their decision-making processes.

## The Future of AI in Video Technology
The future of AI in video technology is poised for significant advancements. We can expect to see more multimodal AI systems that integrate visual, auditory, and textual understanding more seamlessly, enabling more comprehensive video analysis and generation. Advancements in hardware and algorithms will likely allow for more sophisticated AI operations to be performed in real-time, even on mobile devices. We can also anticipate more tools that facilitate creative collaboration between human artists and AI systems, enhancing rather than replacing human creativity. Future AI systems may be able to understand and respond to emotional cues in video content, enabling more nuanced content analysis and creation.

As AI continues to evolve, it will undoubtedly transform the landscape of video technology, offering new possibilities for content creation, distribution, and consumption while also presenting new challenges to be addressed by technologists, policymakers, and society at large.

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Bitrate

What is video bitrate?

Adaptive Bitrate Streaming (ABS)

Bitrate at api.video

Resolution	FPS	Video Bitrate	Audio Bitrate
240p	18	250 KBPS	96 KBPS
360p	25	800 KBPS	128 KBPS
480p	25	1400 KBPS	128 KBPS
720p	25	2600 KBPS	128 KBPS
1080p	30	4400 KBPS	128 KBPS
2160p (4k)	60	16000 KBPS	128 KBPS