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The difference between progressive download and streaming delivery

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The difference between progressive download and streaming delivery

Streaming

When a business or organization publishes a video on the web or operates a video service, it is important to select a video distribution method.

streaming

On this occasion, we will explain the characteristics and differences between the two distribution methods, “progressive download” and “streaming distribution”.

What is progressive download?
Progressive download is a delivery technology that downloads data such as video and audio and plays them at the same time.

Sometimes referred to as “pseudo-streaming,” the video data is played back as it is saved as a temporary file on a terminal such as a PC or smartphone.

Thus, once the video data is downloaded, it can be freely viewed offline without having to go through the internet.

What is streaming distribution?
Streaming is a technology that transfers audio and video data, plays it back in sequence, and distributes the data to terminals such as PCs and smartphones without saving it.

Streaming distribution uses a dedicated streaming server for video and audio distribution and transfers only the data required for playback, making it suitable for distribution of long duration video such as movies.

Due to the technology to play while data is transferred, if the communication environment is poor, the data reception cannot be maintained and the video may stop in the middle.

Advantages and disadvantages
Let’s take a look at the pros and cons of “progressive download” and “streaming”.

Progressive discharge
merit
Even if the communication environment is bad, smooth playback is possible after the data download is complete.
Since the video data is saved as a temporary file in the terminal, the saved video data can be played repeatedly as long as the cache remains.
Operation is possible without preparing a dedicated streaming server
* Recently, streaming servers are becoming more common.
Demerit
Since the entire video file is downloaded to the terminal and distributed, it is easily copied and no copyright action can be taken.
* Recent video data security
Large video files put a strain on your bandwidth, so they take time to play.
As the number of concurrent viewers increases, the server will become overloaded and viewing will become difficult.
Transmission delivery
merit
Only the video being played is transferred to the user, so if the communication environment is stable, you can comfortably watch long and large-capacity videos.
Since there is no data left on the device, copyright-related measures such as data redistribution and falsification are higher than progressive downloads.
* Recent video data security
By using a CDN, a stable distribution is possible even if the number of concurrent viewers increases.
Reference: What is a CDN that is often used for video distribution?

Demerit
Stable playback is not possible unless the communication environment is protected.
A dedicated streaming server needs to be set up, which requires upfront and running costs.

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Video Distribution Advantages and Disadvantages of High Bitrate Part 2

Bitrate

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.

Bitrate

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.

Video distribution Advantages and disadvantages of a high bit rate

Bitrate

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 a formula
Oval bit rate = video bit rate + audio bit rate

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.

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.

Detailed explanation of bit rates for video and music files

Detailed explanation of bit rates for video and music files

CBR (Constant Bit Rate)

Bitrate is an unavoidable experience in video editing and music production.

VBR

The word bit rate sounds a bit complicated, but of course, video and audio files. It is also often found in various situations, such as mobile phones and internet lines.

What is the bit rate? It’s surprisingly useful to remember it sensually, so remember it.

I think the person who visited this page is a beginner asking “What is bitrate?” , So I would like to explain it in the easiest and simplest way possible.

Bit rate basics
To briefly explain the bit rate, it refers to the amount of data per second for communication, such as video files, music files, and the Internet.

The so-called reproduction and communication are data streams. This stream uses a unit called bps (bit per second) to indicate how many bits flow in one second (per second).

I think it is easy to understand if you can imagine the road that a car passes by. The car is the data and the data stream is the road.

Taking into account that a road with many cars carries many people and luggage, it can be said that a lot of data (information) flows. This is called high bit rate.

On the contrary, if there are few cars in motion, it can be said that little data (information) flows. This is called a low bit rate.

A state in which the amount of data is large and the bit rate of the stream is high

A state in which the amount of data is small and the bit rate is low

Should the bit rate be high?
A high bit rate means a large amount of information. If there is a lot of information, it sounds great, like high image quality for videos and high sound quality for music, but it has a big disadvantage.

The disadvantage of a high bit rate is that it increases the data capacity of a single file. If the data capacity is too large, it can take time to send data to someone or move data between hard drives, making it difficult to manage.

Therefore, the codec was developed to reduce data capacity while maintaining high image quality and high sound quality. I’ll talk about codecs another time, but you need to set the bitrate keeping in mind the balance between image quality, sound quality, and file capacity so that the data capacity is easy to handle.

How to check the bit rate
You can check the bit rate by looking at the detailed information of video files and music files on both Windows and Mac.

How to check bitrate in Windows 10
Click Properties in the context menu of the video or audio file for which you want to check the bit rate.

Variable bit rate

Variable bit rate

Variable Bit Rate

Variable bit rate

Variable Bit Rate

The bit rate fluctuates in a video or music data file. More efficient compression is achieved by increasing the bit rate (large amount of data) in the large change part (vigorous movement) and decreasing (decreasing the amount of data) in the small change part. You can expect the effect of reducing the amount of data while maintaining the quality or the effect of improving the quality while maintaining the amount of data, but it is generally used for the first purpose.

⇨  Bit rate
Source: Asahi Shimbun Publishing Co., Ltd. “Books to open when you have problems with your computer” Information on books to open when you have problems with your computer

Explanation of the ASCII digital glossary.jp “Variable bit rate”
Variable bit rate
Bit rate at which the amount of data changes per unit of time. With the variable bit rate, the bit rate per unit of time can be adjusted according to the state of use of the line and the amount of data to be transmitted, so that the data can be transferred efficiently. Also, when compressing video to mpeg, etc., a compression method by changing the bit rate value according to the video.

Digital Daijisen “Variable Bit Rate” explained
Kahen-Bitrate [Variable Bit Rate]

“Variable bit rate” used in a system, for example, when compressing audio and video data. By changing the bit rate, it corresponds to the amount of data in the scene. VBR. VBR control. → Constant bit rate

What is the difference between CBR / VBR / ABR in audio / video conversion?

What is the difference between CBR / VBR / ABR in audio / video conversion?

CBR vs VBR vs ABR

Bit rate is an index that determines the quality of compressed video and audio. Bit rate is the number of bits per second, and generally the higher the bit rate the higher the quality. However, the file size will increase accordingly.

ABR vs CBR vs VBR

The compression method is the behavior of the bit rate at the time of compression, which is the constant bit rate method (CBR), the variable bit rate method (VBR) or the average bit rate method (Averate Bit Rate, ABR). be classified

Constant Bit Rate (CBR) functions

The compression method with a constant bit rate is called the constant bit rate (CBR) method. Since the bit rate is fixed, it is not only easy to predict the file size after compression, but it is also possible to search for the playback position at high speed. However, in the video there are scenes with little movement and scenes with a lot of movement. problems with such as quality change.

WAVE and uncompressed AIFF are also CBR.

advantage
It is possible to predict the size of the file after compression.
You can search the playback position at high speed.
Disadvantage
Quality tends to vary
Variable Bit Rate (VBR) Features
The compression method by changing the bit rate is called the variable bit rate (VBR) method. The VBR scheme places the jitter data with a high intense bit rate, the jitter is compressed by lowering the loose position, in its entirety the quality is kept constant can be compared with the CBR can be compressed with high quality if it is said. However, the size of the compressed file is unpredictable because the bit rate changes from moment to moment. Also, it takes longer to find the playback position than CBR.

advantage
Easy to control quality
High quality

Disadvantage
Difficult to predict compressed file size
It takes time to find the playback position.
Average Bit Rate (ABR) functions
Although the bit rate is variable, the compression method with a constant average bit rate is called the Average Bit Rate (ABR) method. Although the bit rate fluctuates with this method, the size of the final file can be predicted to some extent because it is compressed so that the average bit rate of all data is constant. This allows you to keep the quality as VBR and predict the file size as CBR. However, it takes longer than other methods because the data must be scanned at least once before compression.

advantage
It is possible to maintain quality to a certain extent.
File size can be predicted to some extent
Disadvantage
The compression process takes time

How to get the correct bitrate

How to get the correct bitrate
appropriate

bit rate

Here’s a simple way to get the correct value:

Bit Rate

Don’t increase the frame rate too much
Change the codec type
Check the resolution
If you’re taking up too much CPU on your computer with high-bit video, try the following.

Don’t increase the frame rate too much
Don’t lift too much

Since the frame rate is edited with basically the same settings as the frame rate when recording a movie, if you don’t increase the frame rate too much at the shooting stage, you can naturally keep the bit rate low and reduce the amount of data. may. Even if the resolution is a bit high, if the frame rate is low, like 24fps, there is no problem even if the value is low.

Change the codec type
Change type

By changing the type of program called a codec that compresses and converts audio and video data, it is possible to save high-quality videos even at low values. The codec type can be configured at encoding time, and the recommended codec is determined by the medium the video uses, so try switching to a better performing codec within the recommended encoding and range.

Check the resolution
check

Unless you have a specific purpose, the quickest way to lower the bitrate is not to edit with high image quality, such as 4K video. High-resolution videos have a large amount of information, so it is only natural that the bit rate is high.

So if lowering the resolution doesn’t reduce viewer comfort, try lowering the resolution a bit.

abstract
In this article, I explained the term bitrate, which is a must for anyone editing video. It seems a bit difficult compared to frame rate and resolution, and you should be able to set the proper bit rate by referring to this article.

By setting a suitable bitrate, you can create a video that is easy to handle with a small amount of data while maximizing the quality of the video.

The following article explains in detail how to edit videos.

[Video Editing Guide] Explains how to edit videos in 7 steps

Anyone can easily create video ads and video content. It acquired the number one share in the advertising and media industry for the second year in a row. (* 1) It has been introduced in more than 400 companies, mainly large companies, advertising agencies and production companies.