The video format conversion bit rate

Image quality, i.e. clarity, is a combination of several factors, in addition to bit rate and resolution, including frame rate.

Video formats basic knowledge quote: We tell you about MKV, MP4, H.265, bitrate, color depth, etc. – 4K Knowledge Encyclopedia – 4K China Forum – 4K123!

This tutorial is meant to cover some basic video and audio concepts and terminology. You can answer the following frequently asked questions in more detail:
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What is the difference between these MP4/MKV formats? Which image is better?
How is the video bitrate calculated? Why is it the same 1080p video, some big and some small?
In what format is the image information stored in the video? Is it the same red, green and blue as the monitor?
What exactly does 8bit/10bit mean? Why is it necessary to watch 10-bit video on an 8-bit monitor?
yuv420/444 What do these signs mean? Which is better?
What exactly do lines, planes, textures mean? Why does the video have high and low frequency?
The higher the bitrate, the better the video quality?
This tutorial will be described in detail in the following modules:
1. Encapsulation format (MP4/MKV…) vs media format (H.264/FLAC/AAC…)
2. Basic video parameters: resolution, frame rate and bit rate
3 Image rendering method: RGB model vs YUV model
4, color depth
5, medium chroma sampling
6, low frequency and high frequency in space: plane, texture and line
7, low frequency and high frequency over time: dynamic8
, clarity and brief description

image quality 1. Packet format (MP4/MKV…) vs. media format (H.264/FLAC/AAC…)
MP4+MKV is the most common type of video files you download. These files are actually similar to a package and their suffix is ​​the packaging method of the package. These packages contain video (image only), audio (sound only), subtitles, etc. When the player is playing, please unpack the package first.(The professional term is called separation/division), take out the video, audio, etc., and then play it.

Since they’re just one package, that means the suffix doesn’t guarantee what’s inside or how much. Each element of the package, we call it a track, generally has the following:

Video (Video): In general, there should be, but there are exceptions, such as external audio track in mka format, in fact, there is no mkv video. Please note that when we talk about video, we do not include sound.
Audio (audio): Generally speaking, there should be, but in some cases it is muted, so there is no need to bring it.
Chapter: The segment information that came with the original Blu-ray disc. If the file is checked out, you can see the effect with the chapters in the player:
.potplayer right click screen, option-play-show marker/chapter marker in progress bar.mpc -hc
right click screen, option-setting-on Progress bar shows chapter mark subtitles
(Subtitles): Sometimes the file comes with subtitles, and the subtitles are not directly embedded in the hard subtitles of the video, so they are packed together in the packing container.
Others may have attachments etc which are not listed one by one. There is not necessarily a single track for each type, as MKVs with multiple audio tracks are often seen.

Each track has its own format. For example, it is often said that the video is H.264, the audio is AAC, these are the formats of each track.
Common video formats are H.264 (can be subdivided into 8bit/10bit), H.265 (currently also subdivided into 8bit/10bit), RealVideo (common in early rm/rmvb), VC- 1 (Microsoft-led, common in wmv). Basically H.264=AVC=AVC1, H.265=HEVC.
There are four common audio formats: FLAC/ALAC/TrueHD/DTS-HD MA, which are lossless, and AAC/MP3/AC3/DTS (Core), which are four lossy.

MKV vs MP4, the main differences are:

1. MKV supports encapsulation of FLAC as audio, while MP4 does not. But MP4 can also encapsulate lossless audio tracks (like ALAC, although it is generally believed that the efficiency of ALAC is not as good as FLAC)
2. MKV supports encapsulation of subtitles in ASS/SSA format, but MP4 does not. The subtitles produced by the general subtitle group are in ASS format, so internal subtitles are more common in the MKV format.
3. MP4 is an industry standard and its compatibility with video editing software and playback devices is generally better than MKV. That’s why vcb-s basically chooses the MP4 package for those videos that are optimized for mobile devices.
Beyond that, the two formats are largely interchangeable. For example, they all admit

What is the bitrate of the mp4 video?

The mp4 video bitrate is usually set to around 800.

The basic algorithm is: bit rate (kbps) = file size (KB) * 8 / time (seconds), for example, D5 disk, the capacity is 4.3G, which takes into account the different audio formats, it is calculated as 600M, (so the remaining capacity is 4.3*1024-600=3803.2M), so the video file should be no more than 3.7G.

And if the capacity of the video file is 3.446G and the length of the video is 100 minutes (6000 seconds), the calculation result: the bit rate is approximately equal to 4818kbps (3.446*1024*1024*8/6000= 4817,857).

Bit Efficiency:

1. The bit rate in sound refers to the amount of binary data per unit time after converting the analog sound signal into a digital sound signal, which is an indicator to indirectly measure the audio quality. The principle of bitrate in video is the same as in sound, both refer to the amount of binary data per unit of time after the analog signal is converted to a digital signal.

2. In channel coding, a source data block of symbol size K is mapped to a codeword of symbol size N through coding, and K/N becomes the code rate, where assumes that the symbol table before and after encoding does not change.

The frame rate of 29.97 is the best.

usually:

1080*720 split resolution is about 5000K;

720*576 resolution is about 3500K;

640*480 resolution is about 1500K.

Extended information:

Some code rate principles:

1. Bitrate is proportional to quality, but file size is also proportional to bitrate.

2. If the bitrate exceeds a certain value, it has little effect on the image quality.

3. DVD capacity is limited, whether it is 4.3G standard, overdubbed or D9, there are limits. The information in the computer is represented by binary 0 and 1, and each 0 or 1 is called a bit, which is represented by a lowercase b, that is, bit (bit); uppercase B is byte, ie byte, one byte = Eight bits, ie 1B=8b; the capital K in front means 1024, that is, 1024 bits (Kb) or 1024 bytes (KB). Indicates the size of the file, usually using bytes (KB) to indicate the size of the file.