Understanding Video Bitrates and Codecs

Free Download Mp4Gain

Understanding Video Bitrates and Codecs

Video bitrate and codec are two important concepts that every video creator should understand. In this article, I will explain what they are, how they work together, and how to choose the right settings for your videos.

What is Video Bitrate?

Video bitrate is the amount of data that is encoded per second in a video file. It is measured in bits per second (bps), or kilobits per second (kbps) or megabits per second (Mbps).

The higher the bitrate, the more data is encoded, and the higher the quality of the video will be. However, a higher bitrate also means a larger file size.

What is a Video Codec?

A video codec is a software program that compresses and decompresses video data. It is responsible for encoding the video data into a format that can be stored or streamed, and then decoding it back into its original form when it is played back.

There are many different video codecs available, each with its own strengths and weaknesses. Some of the most popular video codecs include:

H.264: This is the most widely used video codec. It is a lossy codec, which means that some data is lost during the compression process. However, H.264 is very efficient, and it can produce high-quality video with a relatively small file size.
H.265: This is a newer codec that is designed to be more efficient than H.264. It can produce the same quality of video with a smaller file size.
VP9: This is a free and open-source video codec that is developed by Google. It is similar to H.265 in terms of efficiency, but it is not as widely supported.

How Do Bitrate and Codecs Work Together?

Bitrate and codec work together to determine the quality and file size of a video. The higher the bitrate, the more data is encoded, and the higher the quality of the video will be. However, a higher bitrate also means a larger file size.

The codec determines how the video data is compressed. Some codecs are more efficient than others, and they can produce the same quality of video with a smaller file size.

How to Choose the Right Bitrate and Codec for Your Videos

The right bitrate and codec for your videos will depend on a number of factors, including:

The intended use of the video. If you are uploading your video to YouTube, you will need to choose a bitrate that is compatible with YouTube’s streaming requirements.
The target audience. If you are creating a video for mobile devices, you will need to choose a lower bitrate than if you are creating a video for high-definition televisions.
The file size. If you are limited by the file size, you will need to choose a lower bitrate.

Final Words About Video Bitrates and Codecs

Video bitrate and codec are two important concepts that every video creator should understand. By understanding how they work together, you can choose the right settings for your videos to ensure that they are both high quality and have a reasonable file size.

I hope this article has been helpful. If you have any questions, please feel free to leave a comment below.

Bonus Tips

If you are not sure what bitrate or codec to use, you can always start with a high bitrate and then lower it until you find a balance between quality and file size that you are happy with.
You can use a video bitrate calculator to help you determine the right bitrate for your videos.
There are many different video codecs available, so it is important to do some research to find the best codec for your needs.

Free Download Mp4Gain

Mp4Gain Main Window

Mp4Gain Features

Free Download Mp4Gain

What is a bit rate? Basic bit rate knowledge required for video distribution.

Video Bitrate

Bit rate / bit rate

BitRate

Bit rate is the amount of data per second. Video quality is determined by factors such as “resolution”, “frame rate”, “bit rate” and “codec”. Bit rate is an important factor related to video quality. Therefore, this time, I will explain the basic knowledge of bit rates required for Internet video distribution.

” Table of Contents ”

1. What is a bit rate?
2. Relationship between video bit rate and video image quality
3. Estimated video bit rate
4. Advantages and disadvantages of a high video bit rate
1. What is a bit rate?
The amount of data per second is called the bit rate. Use bps as the unit. This is an abbreviation for Bit Per Second. For example, if it is written as 500 kbps, k is 1,000, which means “the amount of data of 500,000 bits per second.”

There are two types of video bit rates: “video bit rate” and “audio bit rate”. The total value of “video bit rate” and “audio bit rate” is the total bit rate (oval bit rate) of the video file.

Video Bit Rate / Audio Bit Rate

■ Voice bit rate
The audio bit rate is the bit rate associated with the audio in the video file. Generally, the audio bit rate is lower than the video bit rate.
The guideline for the audio bit rate is as follows.

Lossy codecs like MP3, AAC, WMA … 96kbps-128kbps
Sound quality oriented video … 192 to 320 kbps
A codec is a program that encodes (encodes) / decodes (decodes) video and audio data. A lossy codec is a codec that dilutes the data and reduces its weight without affecting it. For more information on codecs, see the following.

[Reference article] What is a codec? Basic knowledge of the codecs required for video distribution.
■ Video bit rate
The video bit rate is the bit rate of the video in the video file. Generally, the video bit rate value is higher than the audio bit rate. The appropriate video bit rate will differ depending on the size of the resolution and the content of the video, such as amount of movement / small amount of movement.

The guideline for video bit rate is explained in “3. Guideline for bit rate”, but the value varies depending on the image quality you want to deliver, such as 500 kps to 70 Mbps. Since the standard for audio is “approximately 96 kbps to 128 kbps”, the video bit rate occupies most of the bit rate of the entire video file.

It can be said that the higher the value of the video bitrate, the better the image quality, but that does not mean that “the higher the value, the better”. When displayed at a small resolution, the roughness is not as noticeable even if the bit rate is reduced. On the contrary, even if you encode at a high bit rate, you will not notice the difference in image quality, and in many cases the file size will only increase.

From now on, we will focus on the bitrate of the video.

What is the encryption mechanism? Part 2

Video Bitrate

However, in the case of moving images, the quality of the image at the time of encoding will vary depending on whether the video material has a lot of movement or the video material has little movement, even if the bit rate is the same. Therefore, it is necessary to thoroughly judge and encode not only the bit rate, but also the frame rate and keyframe settings, which will be explained later, according to the video material. I hope you understand that “there is a relationship between resolution and proper bit rate” as a determining factor for high definition.

videro bit rate

Point 2: Increase the frame rate if movement is important and lower the frame rate if image quality is important.
While the frame rate (number of frames) is set at 29.97 fps for televisions and 24 fps for movies, the frame rate is freely configurable for Internet video encoding. A video is a collection of continuous images (frames) like a flip book. The more frames per second, the smoother the movement.

In video encoding, the bit rate per second is fixed, so if you increase the frame rate, the number of images in the flip book will increase and the movement will be smoother, but the amount of data allocated per frame will decrease, so the image quality will be better to fall.
On the other hand, if you reduce the number of frames, the number of images in the flip book will decrease and the smoothness of the movement will be a little slower, but the image quality will improve because a large amount of data will be allocated to each frame. .

If you want to emphasize the smoothness of motion in a video with a lot of motion, increase the frame rate (video demo 1). On the other hand, if the video has little movement, it is not necessary to increase the number of frames as much (depending on the degree), so it is effective to lower the frame rate and give priority to improving the image quality

Point 3: insert “keyframes” at short intervals for moving images
A keyframe is a frame that exists as a single still image (an image that is not compressed between frames) and is the starting point for difference information. Depending on the encoder settings, the keyframes are inserted when there is a scene change and the difference information is inserted at regular intervals, such as XX frames and once every XX seconds.

■ Keyframes for moving images
In a moving image, things move or change significantly in a short time. Therefore, inserting keyframes at short intervals improves the reproducibility of small movements.
There is also the advantage that the search is smoother for images with many keyframes. The reason is that the search is based on keyframes, so the more keyframes you have, the easier it is to stop at the target scene. If the position where the search stops is not a keyframe but a difference information frame, the information is fetched to a nearby keyframe, but that time is short.
However, if you increase the number of keyframes too much, the keyframe bit rate will be taken over and the overall video quality will deteriorate, so be careful.
For moving images, the keyframe is approximately once every 3 seconds.

■ Keyframes for images with little movement
Since there is little difference information in a video with little motion, you won’t notice much difference in change even if there are few keyframes. However, if you insert keyframes for too long, search may not work properly and playback may take a long time to start. This is the opposite of the case where there are many keyframes, and if the rewind position is far from the keyframes, it will take time to read.
For those with little movement, the guideline for keyframes is approximately once every 6 to 8 seconds.

So far, “What is the encoding mechanism? Five points to consider for encoding HD video [Part 1]”, “Understanding the appropriate bit rate for the resolution you want to distribute”, motion oriented or image quality I explained three points how to change the “frame rate” and “how to insert keyframes” depending on whether it is important. In [Part 2], we will explain “the advantages and disadvantages of bit rate settings

What is the encryption mechanism?

Video Bitrate

5 points to consider for HD video encoding

Video Bit Rate

Encode

The image quality of Internet videos is almost proportional to the bit rate. However, if the bit rate increases unnecessarily, the file size will increase. “Keep bit rate low”, “Reduce file size” and “Reduce load time” are linked, and there is nothing to say if you can encode in high definition while keeping the bit rate low.
Also, at the beginning, I wrote that “image quality is almost proportional to bit rate”, but I think some of you may have experienced that “I increased the bit rate and encoded, but I am not satisfied with the quality of the image. “So, this time, I will explain five points that are often used to do high definition video encoding.

Encoding Mechanism
First, I will briefly explain the encoding mechanism.
An image is a collection of continuous images (frames), and by changing this in a short time like a flip book, it appears that you are visually moving. Japanese television images are 29.97 frames per second (short for 29.97 fps / frame per second) and most movies and animations are standard 24 fps. Since a large number of frames are required for video, the amount of data is also huge. Therefore, data compression is indispensable for distributing videos on the Internet.

When coding

“Prediction in frame” that compresses data within a frame
“Prediction between frames” that compresses data into consecutive frames
The information is reduced to the extent that it does not affect the visual sense and the data is compressed.

■ What is in-frame prediction?
There are various methodologies for data compression, so I will skip the details here, but the basic idea of within-frame prediction is to divide a frame into small blocks called cells and the colors adjacent to each other in the block. they are the same or similar, they are compressed together.
For example, if there is information “blue blue blue blue blue blue blue blue blue blue red red yellow yellow yellow” information in the divided block, the amount of data can be reduced by combining this with “blue 11, red 2, yellow 3”. It’s an image.

An example of data compression in in-frame prediction (image)

■ What is cross-frame prediction?
However, in the case of video with a time axis, the number of frames is large, so there is a limit to the overall weight reduction based solely on the prediction within the frame. On the other hand, in the prediction between frames, based on the idea that “the contents are similar before and after the consecutive frames”, the cells that do not change from the previous frame reduce the amount of data by reusing information, and the cells that change is converted to data as difference information.

Point 1: learn a suitable bit rate guideline for resolution

The above three are excerpts of the same 640x360px image, but the file sizes are different at 1MB, 250KB, and 50KB. The image quality of 250 kB is lower than that of 1 MB and is much coarser at 50 kB. This is because the amount of data allocated per pixel is reduced, resulting in poor image quality.

The same phenomenon can be said of the videos. Bit rate is the amount of data allocated per second and affects the image quality of the video. If you want to view a video on a large screen, such as viewing it full screen on a computer or TV monitor, you need a sufficient bit rate according to the resolution. On the other hand, when displayed at a small resolution, the roughness is not as noticeable even if the bit rate is reduced. On the contrary, even if you encode at a high bit rate, you will not notice the difference in image quality, and in many cases the file size will only increase.

What is the bit rate?

What is the bit rate?

The bit rate, or as they also say the width of the stream, is the amount of data transmitted or processed in 1 second. The concept mainly applies to multimedia content, for example, video bit rate is nothing more than the amount of video information that is displayed on the screen in one second. To measure the bit rate, the designation “Kbit / s (kbps)” is used, that is, kilobits per second, less frequently Mbit / s, and so on. The more information that is transmitted during a specific period of time, the higher the quality of the image.

When people say “low bit rate video” they are generally referring to low quality video. Blur, opacity, and pixelation are characteristic features of such video, while high-bit-rate video has a detailed image with a rich color gamut. Like video, audio also comes with low and high bit rates. Music with a low bit rate loses in the frequency range, words and chords become less distinguishable, and itself takes on an unnatural sound, as if it were an electronic sound.

Bit rate types

It is not enough to understand what the video or audio bit rate is. To successfully work on programs for editing and converting multimedia content, you need to know what types of bit rates exist. These are constant, variable, and average, and each of them can be used in a specific situation.

Constant bit rate

Constant refers to a bit rate that does not change throughout the file, providing an accurate estimate of the size of the output material. On the other hand, it is not very suitable for multimedia with dynamically variable audio and video streams, as it does not provide an optimal balance of size and quality. Constant bit rate is mainly used at home level, as well as when processing files with relatively constant picture and sound characteristics.

Variable bit rate

In files with variable bitrate, the latter is changed by the codec for each frame according to its characteristics. For example, in frames that are not very informative and easy to encode, the video bit rate is lowered, which saves space, and this saving can differ significantly. Variable bit rate technology is often used to achieve the best quality / size ratio. The downside of this method is the unpredictability of the final size of the media file.

Average bit rate

A more flexible option is the averaged bitrate, which is a hybrid of the first and second types. Unlike Variable Bitrate, by choosing Average Bitrate the codec can only work within the user defined range. Professionals use this method when creating large projects, allowing you to achieve high-quality encoding with a relatively small file size. The precision of calculating the size is much higher.

How to find out the bitrate of the file

Novice users are often interested in how to find out the video bit rate and if special programs are needed for this. With few exceptions, it is not necessary to use third-party tools for these purposes, since the bit rate of the file can be obtained by the operating system itself. Right-click on the video file and select “Properties” from the menu. Then switch to the “Details” tab in the window that opens and look for the item “Data transfer rate”. This will be the bitrate of the video. In the case of audio files, the item will be named “Bitrate”. If the required information is missing from the properties, for example in the case of MKV files, use the MediaInfo utility.

What bit rate value to set

But much more relevant is the question of what bit rate should be set for a video when creating or converting it. It will not be possible to answer it unequivocally, it all depends on the situation and the purpose of the content. If you focus on average values, you should configure 2.5-5 Mbit / s for video and approximately 192 kbit / s for audio. When choosing, you should also consider the video format. Therefore, for 1920 x 1080 SDR video, the bit rate is better to set 8 and 12 mbps (60 frames / s), and for HDR video with the same resolution – 10 and 15 mbps, respectively.

What is the bit rate?

Bit rate measures the speed at which information can be transmitted between two locations. The standard unit for this speed is “bits per second”, but a kilo or mega value is often prepended to indicate the high speeds of modern digital technology. Communication technology measures speed as a function of bit rate, especially on the Internet. The transfer rate indicates how fast the data can be downloaded. This measure is also widely used to describe audio and video. higher rates mean higher quality.

In its simplest form, bit rate describes how many bits per second are transmitted between two different locations. The higher the rate, the faster information can be exchanged between them. For this reason, the bit rate can be particularly important for communication technologies such as broadband, as it defines how quickly a user can download or upload information.

The standard unit for bit rate is bits per second (bps). However, this measurement is often too small to be practical in modern communication technology, as millions of bits can be transmitted per second. To solve this problem, the device is usually prefixed by a different letter indicating its size. For example, kbit / s means kilobits per second or 1000 bits per second. Megabits per second are written as Mbit / s and represent millions of bits per second.

Bit rate is an important measure for a large number of different areas of computing. Broadband, for example, is often specified as a certain number of Mbit / s, with speeds of around 2 Mbit / s being common. Fiber broadband, which is much faster, can deliver speeds of up to 5 Mbps. This measure also describes the speed of mobile connections such as 3G and Bluetooth.

Audio and video quality are commonly reported in terms of bit rate, with higher rates indicating a higher quality picture or sound. In multimedia, this metric is a quick way to show how much information is stored in each second of recording, so higher rates lead to increased quality. The bit rate can depend on a variety of factors, including whether the information has been compressed.

The standard bit rate for audio is between 100 and 160 kbit / s, while higher quality recordings can reach up to 320 kbit / s. Video speeds can be significantly higher for Blu-ray discs with speeds up to 40 Mbps. Standard DVDs are only about 9 Mbit / s, so there is a difference in quality.