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What is bitrate in a video? | Improve QUALITY

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Video Bitrate

Bitrate is, without a doubt, one of the main characteristics that determine the quality of a video.

I’m glad you made it this far to continue learning about video. If you still don’t know about video or editing, remember that you can learn the basics with my video courses (among others).

bit rate

What is video bitrate?

The bitrate or bit rate is the amount of information per second that the video has. It is measured in megabits per second and is directly proportional to its quality.

Generally, we tend to confuse the size of the video with its quality, thinking that 4k size is the video that offers the highest quality. However, this is flatly incorrect.

A high bitrate offers quality: Size VS Quality

Continuing with the topic I was talking about, it is very common for videos with 4k (at least those from professional cameras) have a higher bitrate. This is what makes the video look better quality, mainly, regardless of whether the video is larger or smaller.

How do you notice the difference between a high bitrate and a less high one?

The bitrate tends to show significant differences not simply when recording, but when editing. As I have already told you, with a bitrate of 10-15 mbps / s (at 25 fps) you have more than enough for most jobs. However, and if you are very exquisite, you may want to use a higher bitrate to have more margin for error when correcting and color grading. By the way, if you are interested in learning about color correction and color grading, check out my course.

With a higher bitrate you will notice the following differences than with a lower one:

Sharpness increase.

Superior ability to edit color without the appearance of banding or other unwanted disturbances.
Greater file weight (the higher the bitrate, the larger the file occupies).
However, this is not to say that it will be noticeable for most jobs. If you work in events, I assure you that you will not have a problem.

Bitrate types

If you are one of those who want to know more about everything you study, you can stay and delve deeper with me.

There are two types of bitrate, the constant bitrate and the variable bitrate.

CBR: this is the bitrate that always, whatever is on the plane, the exact same transfer rate will be used. The good news is that a video recorded at a specific size and bitrate will always occupy the same amount. However, it is not the most efficient.
VBR: this is the variable bitrate, and it consists in that a different bitrate will be applied depending on the information that is being recorded. Obviously, if you are recording a super dark black background, you don’t need as much information as if you are recording a scene with a very wide color gamut and a histogram that is padded from blacks to whites. In this case, the bit transfer rate will vary according to the needs of what is being recorded. Of course, we will try to keep an average (the chosen one).
How to know the bitrate of a video, both on Windows and Mac?
I am going to explain to you, both for Windows and Mac, how to find out the bitrate that a video clip has. This is very good because you can see that a video loses quality the more compressed it is. And one of the ways to compress it is by lowering the bitrate.

Windows: right-click on the clip> properties> details tab> video section> total bit rate
Mac: you open the video with the quicktime player> while it is playing press cmd + I> data rate
It is important that you pay attention to whether this data is in kbps or in mbps, because the first is 1000 times less than the second (so that you take it into account in case you want to compare looking from two different computers).

When to compress a video by lowering its bitrate?

There are times when you have already finished editing the video and obviously want to compress it. For this I recommend that you learn about codecs and video formats.

Obviously when you compress the video you will lose quality (the bitrate will decrease). This, a priori, should not be noticed in excess if it is a good compression, since you will no longer edit that video.

Of course I am talking about compressing the final file, never the raw ones used to create the video. You always have to lower the bitrate or compress the final file (in case you want to compress) to avoid losing image quality.

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Bit rate factor – how does it contribute to video quality?

Bit rate is a very important factor for good video quality. In the camera settings we now find more numbers next to the resolution. The one behind Mbps interests us more now. This is the information about the bit rate.

Video Bit Rate

This number indicates how much information is processed in the video per second. The higher this rate, the better the quality. Of course, the final file the camera produces will increase with the bit rate.

In this way, you can also calculate how much information is available for each frame, that is, each individual image. Suppose you are shooting with 25p and you have an available bit rate of 100 Mbps. That would mean that each image carries 4 Mbps of information. If you shot 50p at the same bit rate, it would only be 2 Mbps per image! The result would be a loss of image quality.

Color depth factor – How does it contribute to video quality?

Bottom line: color depth is the maximum number of different color shades that a camera can display. Of course, the same applies to monitors, printers, televisions, etc.

The colors in general in our image consist of additive combinations of the three basic colors red, blue and green.

The gradations in each tone are again given in bits. Videos consist of pixels, that is, square image points. Each of these pixels carries with it certain color information. The higher the bit rate of the color depth, the more different shades of color each pixel can have.

The total number of color tones is calculated by adding 2 to the power of the number of bits; for an 8-bit camera, for example, that would be 256 colors per base color. Now you have to multiply the other two basic colors again to determine the total number of possible color tones. This means that an 8-bit sensor can display 28 * 28 * 28 colors. That’s over 16 million shades!

Thus, a 10-bit camera can display more than 1 billion colors, a 12-bit camera 68 billion colors, and a 14-bit camera even more than 4 billion color combinations.

Summary:

Many users are not fully aware of how bit rate influences video quality.
People usually see numbers next to the name of the format (Mp4, MOV, AVI) and do not know exactly what it is.

Here we have tried to explain that the higher the bit rate, the more colors.
Perhaps you think that speaking of so many millions of colors, and it is enough, but it is not like that. Actually reality has a practically infinite number of color gamut, so to capture it with realism, it is necessary to have as many colors as possible.

Definition and explanation of the term bit rate

Bit rate denotes a unit in which the relationship between the amount of data and time occurs. It is measured in the unit of bits per second. Common abbreviations for bit rate are bit / s or bps. The output quantity of information units in relation to digital multimedia formats limited by a constant output time is designated on a timeline.

Bit rate is used in video and audio compression. Encoding is possible with constant (short CBR) and variable (short VBR) bit rate. The variable bit rate aligns the encoding with the content of the multimedia content. In the case of a predominantly quiet scene in a movie, for example, fewer units of information are required relative to time. However, in scenes with a lot of movement, the bit rate increases. This is intended to allow optimal use of storage space with high image quality at the same time when compressing with a codec. Often times the required memory space is also less when encoding with a variable bit rate compared to a fixed rate.

Constant bit rate

Constant bit rate describes a compression method for video and audio content during storage and transmission. A constant data rate is used, regardless of the complexity of the respective signal. The same amount of data is always produced per unit of time.

Constant bit rate is often used in multimedia broadcasts. The reason for this is the limited streaming capabilities. By using constant bit rate, optimal quality is achieved with the same data throughput. In some cases, however, it may also happen that amounts of data are “given away”. This is the case when the content to be encoded requires a lower rate than specified. This is especially true for videos with quiet scenes or very quiet audio files. The constant bit rate is used, for example, for video CDs or Internet radio.

Variable bit rate

In addition to the constant bit rate, encoding with a variable bit rate is also possible. Here is audio and video content in constant quality at different bit rates depending on the content stored or transmitted.

This solution has established itself in the media storage field as it offers higher quality with less memory consumption at the same time. When encoding with a variable bit rate, individual sections of a medium receive different compressions depending on the complexity of the content. This enables the highest possible quality to be achieved with low memory consumption.

For a long time, encoding with the help of variable bit rates was considered insecure. In the meantime, however, the technology has matured, so good results can also be achieved by converting a medium with a variable bit rate. The downside of this method is that you cannot predict before conversion how big the file will be in the end. In most cases, only a minimum and maximum bit rate can be set. Individual encoders also offer the option of specifying how large the file should be before converting it.

Average bit rate

A third compression method is the definition of an average bit rate. A medium is converted at a variable bit rate. This enables a fixed file size to be achieved while maintaining high quality. For this variant of media compression, some codecs offer the option to compress in two passes. This allows the average bit rate to be reached very precisely.

In the first pass, the material is analyzed and then compressed in the second. Basically the method corresponds to that of variable bit rate, but an average bit rate allows you to calculate the size of a file. A deviation tolerance can be specified for individual programs.

Nominal bit rate

Nominal bit rate indicates the average bit rate that is achieved by encoding with a variable bit rate. Despite the possible fluctuations that arise in the various VBR modes, a quality assessment can be made.

The nominal bitrate concept was introduced by the developers of the OggVorbis codec. This should make it easier for MP3 users to start using variable bit rate. Many Mp3 codec users were only used to compressing an audio file with a fixed bit rate.

What is the constant and variable bit rate in an MP3?

The FLAC format is more modern and with less loss of quality than MP3 but with a much larger file size, so MP3 remains one of the most widespread and used digital audio formats. With MP3 encoding at 320 kbps, excellent quality is achieved for most domestic digital audio players and for the human ear itself. But what is the difference between MP3 with a constant bit rate and a variable bit rate? Let’s clear the doubt.

Constant Bit Rate vs. variable bit rate

The variable bit rate coding method, known by the acronym VBR (Variable Bit Rate), is intended to achieve the highest audio quality evenly throughout the entire music track by performing an intelligent bit allocation during The coding process. That is, the Bit Rate varies to keep the audio quality as constant as possible throughout the file. In general, the MP3 encoding method with a variable bit rate produces a higher quality level than the constant bit rate coding for a similar Bitrate encoding.

Constant bit rate coding (CBR – Constant Bit Rate), meanwhile, is an encoding method that, instead of varying the bit rate, varies the audio quality to adjust to a fixed and constant bit rate at length of the MP3 file.

When to use a Constant Bit Rate?

If your priority is to get a certain MP3 file size, or at least a more or less predictable size, you should use a constant Bit Rate encoding.

When using a constant Bit Rate, the final file size is predictable although the quality of the MP3 audio will not be constant along the audio track.

When to use a Bit Rate Variable?

Bit Rate Variable encoding was developed for use when the main priority of MP3 encoding is a consistent quality throughout the track and the final file size is not the most important.

In an audio track some sections will be more difficult to code than others. Coding with Constant Bit Rate will encode the audio at the same Bit Rate set in advance, both in these more complex sections and in the easier sections. On the contrary, the coding with Bit Rate Variable will assign less bits in the easiest sections and will assign more bits when the section requires it because of its complexity. In this way, VBR encoding achieves a more uniform audio quality throughout the entire MP3 while the CBR achieves a constant Bit Rate.

In other words, if you use Constant Bit Rate the quality will be varied to reach the specified Bit Rate while using a Variable Bit Rate the Bit Rate is varied to achieve the highest possible and uniform quality.

All this does not mean that you don’t have to specify a Bit Rate for VBR encoding. Normally a fork will be specified, for example, 192-320 kbps, which means that a minimum of 192 kbps will be allocated for the easiest sections and up to a maximum of 320 kbps in the most complex sections of the music track.

The negative part is that MP3 encoding with Bit Rate Variable is not supported by some players. For me this disadvantage is part of the past and only if you try to play an MP3 in a really old player will not be able to read the file.