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What is the standard bitrate for smartphone videos? Part 3

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What is the standard bitrate for smartphone videos? Part 3

Smartphone

Estimated audio bit rate
In the case of audio bit rate, “128 kbps” is basically a guide.

Smartphone bit rate

Generally, for lossy codecs like MP3, AAC, WMA, AC3, Vorbis, a voice bit rate of around 128 kbps is sufficient. On the other hand, if the video is geared towards sound quality, it should be around “192-320kbps”.

Three Points to Consider When Considering the Bitrate of Smartphone Videos

There are a few things to keep in mind when considering the bitrate of your smartphone video.

When creating a video, you should use the appropriate bitrate for factors like size, but when considering bitrate, you need to keep three points in mind.

Here, we will introduce three points to keep in mind when considering the bitrate of smartphone videos, so why not refer to what kind of points to keep in mind?

Bit rate notes 1: The numbers are just a guide.
The proper bitrate for smartphone videos is just a guide.

The bitrate of a video involves multiple factors, not just the size of the image. For example, if you want to save a video with a lot of movement in high quality and a video with little movement that you want to save in medium quality, the appropriate bit rate will be different even if the image size is the same.

So, consider the bitrate you need as a guide only.

Bit rate note 2: consider the resolution according to your purpose
Let’s decide the optimal resolution according to the purpose of the smartphone video.

Even if you call it a smartphone video, it does not mean that a video with almost no motion and a video with high motion should have the same resolution. It is important to select the one that suits your purpose, such as high resolution for videos showing precise movements and low resolution for videos with little movement.

Therefore, when considering the resolution of a video, consider what the video is about.

For seminar videos
Since the seminar video is almost motionless, no high resolution is required.

The seminars and training videos aren’t particularly poignant videos, so lower resolutions won’t be a problem. For example, there is not a big difference between a low image quality of about 300 kbps and a high image quality of about 1500 Kbps, so it is recommended to make a light and low quality video.

For promotional videos
For promotional videos, it is a good idea to have a certain resolution.

It is not attractive that the resolution is low and that the video does not look beautiful in the video for internal promotion. However, it depends on the content of the video itself, so if you are not sure about the resolution, it is recommended to prepare a higher resolution and a slightly lower resolution and compare them.

For sports videos
High resolution is best for sports videos.

The bit rate has the characteristic that it is required since the difference with the previous frame is greater, and it is necessary to set it higher for videos with a lot of movement.

Therefore, if the resolution of the sports video is low, the outline will be broken and the color will fade, resulting in a stressful video.

Bit rate note 3: consider file size
The higher the bit rate, the larger the file size.

Of course, it depends on the content of the video, but as the bitrate increases, so does the file size, so this needs to be taken into account.

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What is the standard bitrate for smartphone videos? Part 2

smartphone bit rate

Video Terms to Remember 1: Resolution
Resolution is the number of vertical and horizontal pixels in a video.

Smartphone BITRATE

The higher the resolution, the better the image will look. For example, if you prepare the same image with the same resolution of “640 x 360” and “2560 x 1440”, the latter will be clearer in detail.

Also, both the resolution and the pixel refer to vertical and horizontal pixels, but in the case of the number of pixels, it is expressed by the total number, so if the resolution is “1980 x 1080”, the number of pixels will be “2,138,400”.

Video term 2: frame rate to remember
Frame rate is the number of still images per second of video.

The frame rate unit is “FPS (Frames Per Second)”. Since a video is made up of a collection of continuous still images, the higher the frame rate, the smoother the video. However, the amount of data will increase accordingly.

Therefore, it is important to set the frame rate to the appropriate size according to the purpose of the video.

Video Term 3: Codec to Remember
A codec is a codec that compresses and decompresses audio and video data.

The larger the size of the video, the greater the amount of data, and the higher the quality, the larger the file size. Therefore, it is necessary to compress the data with a codec.

For example, there are types such as “MPEG-4” and “MPEG-2” for video codecs and “MP3”, “AAC” and “FLAC” for audio codecs.

Estimated bit rate suitable for smartphone videos

For smartphone videos, the standard bit rate is “300 kbps” or “600 kbps”.

Taking as an example the frame size that is often used for inline distribution, if the frame size is 480 x 270 px, 360 x 270 px, the bit rate is “300 kbps” and if the frame size is 640 x 360 px, 480 x 360 px, the bit rate is “600 kbps” will be a guide.

What is the standard bitrate for smartphone videos?

Bitrate

In this article, we’ll give you an overview of bit rates, guidelines for suitable bit rates for smartphone videos, and points to keep in mind when considering bit rates for smartphone videos, so check them out.

smartphone bit rate

What is the important bitrate for smartphone videos?
Bit rate is a term that refers to the amount of data per second.

The amount of data that can be sent and received in one second, and the unit is “bps (bit per second)”. For example, at 1 bps, 1 bit of data can be sent and received per second, and the higher the bit rate, the more data can be transferred.

Therefore, when making smartphone videos, it is necessary to consider the bit rate that viewers can comfortably watch.

Relationship to screen size
The larger the screen size, the greater the amount of data required and, conversely, the smaller the screen size, the less the amount of data.

Therefore, there is a reference bit rate for each screen size. If the screen size is 480 x 360, the bit rate is 500 to 700 Kbps, if it is HD 1280 x 720, it is around 2000 Kbps, and if it is full HD 1920 x 1080, it is around 4000 Kbps It is a guideline for the bit rate.

Three video terms to remember in advance

When creating a video, be aware of the video terminology.

In recent years, there have been many cases of video distribution in companies. However, there are many technical terms in the video, so you need to know the meaning of the terms in order to understand the video properly.

Here are three video terms to remember beforehand, so why not take a look at what they are?

What if the bit rate is high?

Bitrate

High bit rate = a lot of data can be transferred per second

bitrate
.

Sounds like a good thing.

The network cameras managed by my company send the captured video data to a personal computer for viewing over the network.

If you want to see the video, you want to see a beautiful video that moves sharply with high image quality, right?
However, the amount of data in a beautiful image is surprisingly large …

In such case, if the bit rate is high, a lot of data can be transferred per second, so you can deliver beautiful images to your computer. On the other hand, if the bit rate is low, the amount of data that can be transferred per second is small, resulting in choppy and poor quality moving images.

“Then the bitrate should be high anyway!”

… That is not the case.
In fact, in a surveillance camera system, there are the following disadvantages to increasing the bit rate.

Disadvantages of high bit rate!
Transferring a large amount of data increases the load on the network line and equipment.

There is an upper limit to the bit rate that can be transferred depending on the network environment. This depends on the LAN cable you are using, the performance of the hub, etc., but it will be difficult so I will skip it. Just think that there is an upper limit for the bit rate depending on the environment.

“So what happens if it exceeds the upper limit?”

In the case of video from a network camera, the connection often drops. If you exceed the upper limit, the line will be punctured and you will lose connection with the camera. The image may be interrupted for a moment, but if it is too bad, you will not be able to see the image from the camera at all.
If this happens, it will be very troublesome …

Also, if the bit rate is high, a large amount of data will reach the browsing computer and the recording NVR. When a lot of data arrives, the computer or NVR will not be able to process the data, which may cause abnormal operation (reboot, etc.).

Therefore, the System Kay NVR defines the maximum bit rate that can be supported as a specification. The bit rate that the entire NVR can process such as performance and bandwidth limit per channel are described in the specifications.

Video distribution Advantages and disadvantages of a high bit rate

The video bit rate is calculated separately for video and audio and added together.

Bit Rate

The sum of the video and audio bit rates is called the oval bit rate (total bit rate).

Expressed in the formula
Oval bit rate = video bit rate + audio bit rate

Will be.

High bit rate benefits
The higher the bit rate, the better the picture and sound quality, and the lower the bit rate, the worse the picture and sound quality.
However, note that if the video bit rate is high, there are cases where the video bit rate is high and the image quality is good, but the audio bit rate is low and the sound quality is poor. On the contrary, there may be cases where the image quality is poor and the sound quality is good.

High bit rate video basically has the advantage of improving image quality and sound quality, but you also need to understand the disadvantages.

Disadvantages of high bit rate
The higher the bitrate, the more net bandwidth is consumed and the more playback load is applied.
For example, increasing the bit rate from 500 Kbps to 1000 Kbps doubles the net bandwidth usage and doubles the playback load or more.

It is easy to increase the bit rate for high image quality, but if you increase the bit rate too much, the CPU will become overloaded and you may not be able to reproduce it well, so be careful.

Especially when the radio wave of the smartphone is bad or the band is limited, it may not play smoothly at a high bit rate.

Even if the bit rate is increased, the image quality and sound quality do not improve above a certain level.
In fact, increasing the bit rate does not mean that the image quality and sound quality will increase without an upper limit.

For example, if the image quality of the original video material shot by the camera is 100, even if it is converted at a high bit rate by video editing software or encoding software, a high-quality video with a quality of 100 or more image of the original video will be created. You can not.

No matter how high the bit rate is, if the quality of the original video material is poor, the quality will not be better.

Let’s think about the optimal bitrate for each video.
When creating a video, you need to think about how to set the optimal codec, resolution, frame rate, and bit rate yourself.

Then
The higher the bit rate, the better the picture and sound quality.
If the bit rate is high, the network and the playback terminal will be overloaded.
Even if the bit rate is increased, the picture quality and sound quality should not be higher than that of the original video material.
It is useful to remember that.

Also, almost all video editing software, encoding software, YouTube, and other free video publishing services commonly used when creating and publishing videos have preset settings with preset codecs, resolutions, frame rates, and bit rates.

However, the image quality of the presets is not always optimal, so use this bit rate knowledge when you need to make fine adjustments.

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.

MP3 bitrate types

MP3 bitrate types

Mp3 Bitrate

Bit rate

bitrate

CBR stands for constant bit rate, that is, a constant bit rate that is set by the user and does not change when the part is encoded. Therefore, every second of the part corresponds to the same number of bits of encoded data (even when encoding silence).

VBR stands for variable bit rate, that is, a variable bit rate or variable bit rate that the encoder program dynamically changes during encoding based on the saturation of the audio material being encoded and the encoding quality set by the user (for example, silence is encoded with the minimum bit rate). The downside to this encoding method is that VBR considers the quietest snippets to be “negligible” audio information, so it turns out that if you listen too loud, these snippets will be of poor quality, while CBR makes quiet and loud snippets with the same bit rate …

ABR stands for Average Bit Rate, that is, Average Bit Rate, which is a hybrid of VBR and CBR: the user sets the bit rate in kbit / s and the program varies it, constantly adjusting it to the specified bit. Velocity. Therefore, the codec will be careful to use the maximum and minimum possible bitrate values, as it runs the risk of not conforming to the bitrate specified by the user. This is a clear disadvantage of this method, as it affects the quality of the output file, which will be slightly better than using CBR, but worse than using VBR (with the same file size).

MP3 codecs

The type of programs required to convert file formats. The most common MP3 codecs are:

mp3PRO-codec (uses SBR frequency transform).
LAME codec
fraunhofer-codec

The concepts of pixel, video pixel, point.

The concepts of pixel, video pixel, point.

In computer graphics, the term “pixel”, broadly speaking, can mean different concepts: the smallest element of the image on a computer screen; a separate bitmap element; dot of the image printed on the printer.

Therefore, to avoid confusion, use the following terminology: in ideopixel: the smallest element of the image on the screen; pixel – a separate element of the raster image; dot is the smallest item produced by the printer.

The display screen is divided into a fixed number of video pixels, which form a graphical grid (raster) of a fixed number of rows and columns. The size of the graphics grid is generally expressed in the form NxM, where N is the horizontal number of video pixels and M is the vertical number. On modern displays, graphical grids are used: 640 x 480, 800 x 600, 1024 x 768, 1240 x 1024, etc. The image on the display screen is created by selectively illuminating certain video pixels on the screen with an electron beam. For an image to be perceived by the eye, it must be made up of hundreds or thousands of video pixels, each of which must be illuminated. ”

Raster graphics are photo quality images. If the pixel sizes are small enough (close to the size of video pixels), then the raster image looks no worse than a photograph. Raster graphics effectively represent photo-quality images.

A large amount of memory is required to store bitmaps.

The bitmap file stores the color information for each video pixel as a combination of bits. Simple bitmap images take up a small amount of memory (several tens or hundreds of kilobytes). Photo-quality images typically require several megabytes. Therefore, a large amount of memory is required to store bitmaps.

Bitmap becomes distorted when scaling.

The bitmap may lose its appeal after scaling or rotating it. For example, areas of solid color can take on an odd pattern (“moire”); curves and straight lines that seemed smooth can suddenly become sawtooth. If you reduce and then enlarge the bitmap to its previous size, it will become blurry and uneven, and the filled areas may be distorted. Bitmaps have very limited options for scaling, rotating, and other transformations

Tasks for which raster programs are used.

Raster graphics allow you to create photo-quality images. After all, what are raster graphics? It is an image that consists of pixels, small squares, each of which is assigned a specific color. On any screen, the information is displayed exactly in raster form.

What do the concepts of pixel, video pixel, point mean?

In computer graphics, the term “pixel”, in general terms, can mean different concepts:

· The smallest element of the image on the computer screen;

· A separate element of the bitmap image;

· Dot of the image printed on the printer.

Therefore, to avoid confusion, we will use the following terminology:

· Video pixel: the smallest picture element on the screen;

· Pixel: a separate element from the raster image;

· Dot: the smallest element produced by the printer.

In this case, for the one-pixel image on the computer screen, one or more video pixels can be used.