How do the audio and video codecs work?

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For what purposes and how are codecs used?

Let’s start with the analysis of the name that is the result of the union of two words CODer and DECoder. In fact, through the codecs it should be possible both to decode multimedia, audio or video files, as well as to create them.
In reality, codecs do not always allow file creation and the reason is often legal or commercial in nature.

Its internal functioning is usually very complex, due to
to the nature of the processing they must perform. While the
The purpose is to allow the expansion capacity of the different players, so that they can see or let us listen to the content of the files written in a format that they did not understand at the time of their launch.

Regardless of the file format, the content is always the same, that is, a movie or audio, intended to be played.
So it was decided to introduce an additional software layer between the file and the player, which filters access to the file itself and that
always makes the player “see” the same type of object even if the file format varies.

In order to use codecs, you first need to know
its existence, which is why in Windows systems there are
parts of the log file, which collect information
on the different multimedia filters installed. Generally, your
Interaction with players is done through COM interfaces.
Simply put, when we tell our favorite player to open a media file, it will do nothing more than retrieve the list of installed codecs and try to open the file with
each. If one of the codecs is successful, the player will use it
to show us or listen to the file.

As we have seen, its use is completely transparent for the user and is completely managed by the player. Some players even manage the installation of the necessary codecs. However, it is also possible to install them manually. On Windows systems, codecs that use COM technology are generally in the form of DLLs that must be registered, a procedure that involves entering all public interfaces of the codec in the registry file.
To do this, you need to run the command
“Regsvr32 <dll name>” while uninstalling it
just add the “/ u” option to the first command.

Other operating systems use some interprocess communication mechanism other than COM, but the structure does not change. That is, it is always a filter to access the file.

The existence of different formats and related CODECs arises for technical and commercial reasons. Different multimedia companies usually prefer to define their own encoding formats, to optimize their use by their applications.
And in addition to this, by defining their own format, they are not obliged to pay user licenses
. This mainly applies to file generation; in fact, many codecs are simply decoders.

In this way, companies can add read support for various formats to their applications at no additional cost, while using their proprietary format for saving.

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What is a codec?

What does codec stand for?

The word codec is a new word invented to display the encoding and decoding programs of video and MP3 files (remember that a file [reading error] is a series of numerical values that make up a text, a song or a video consists of data from a file, a card, etc. etc., which are stored and transferred on a computer, on the hard disk, on an SD card or a USB stick, on a smartphone and transmitted via the Internet, Bluetooth , WIFI). There are several CODECs because different techniques have been developed to process a video or audio file in order to save memory and transmission space (so-called memory byte allocation or GIGA …). Sometimes our computer may not be able to read a video that we receive, downloaded from the Internet, or recorded by the home video surveillance system. Here there is a need to install a suitable codec for reading the video.

Where do you download a codec? Where can I find the right codec for reading the video? Where can I download the audio codec?
To find out which codec we need, we turn to small special programs that examine the contents of the file and find out which codec was used to encode the file and consequently for subsequent reading. In our article: How to find out the format of a video or song (here), we illustrate this process.

To download the required codec, we can do a search on Google, Bing or another search engine or connect to one of the many websites where codecs are collected both individually and in packages.

The best-known codec collection on the Internet is the K-LITE codec package, which you can download from the well-known Italian website html.it.

The most popular audio codec is undoubtedly MP3, the result of mathematical and psychoacoustic studies that allow you to compress an audio track in its original format, saving a lot of space. The introduction of the MP3 codec revolutionized the music world on the PC (and later on the advanced audio devices), since on average 90% of the storage space and thus the transfer of a file was saved by audio. The format used in Windows was called .wav (remember that the period followed by three letters indicates a file extension to indicate to the programs / operating system what a file contains and to match the correct reader / processor).

The best-known video codec for the Windows world was .avi (Interleaved Audio – Video).

What are audio and video codecs?

Codecs are software or hardware devices that digitally encode and decode (compress) an analog signal.

It will happen to you that at least once in your life you cannot play a video file like a movie or a piece of music and wonder what the reason for this obstacle is. The bug in the above cases is the program for watching movies and listening to music: it does not have the required codecs.

Audio and video codecs are key elements for the proper functioning of a computer system, even if they are not known to the public. Without a suitable codec, however, computers (or smartphones and video game consoles and even decoders that watch TV at home) would not be able to play music or display pictures from a film. Our ability to relax and watch a movie or listen to the music of our favorite actor or singer depends on the codecs.

What are audio and video codecs?

An acronym for encoder / decoder is a codec or software device that converts an analog signal such as the sound wave of a song into a digital data stream. This way, your computer or other computing device can easily play photos, videos and songs. Codecs are also used to reduce the size of audio and video files that result from analog-to-digital conversion. Without compression technology, digital files would be huge and difficult to manage from computers and smartphones.

Two compression techniques

There are two compression techniques: loss and loss. The first system is lossless and the second is lossless. Let’s take another example. Let’s say we want to insert analog video with lossy compression: we have a small file, but not exactly good audio and video quality. If we choose the second technique (no loss), the file is “heavier”, but has a higher audio and video resolution.

The best quality

Compression removes some of the elements that make up the video. Lossy compression codecs remove more data than lossless compression codecs. In recent years we have been working to optimize the quality of compression. For example, the new HEVC standard (High Efficiency Video Coding), also called H.265, offers a better ratio of quality to compression. In practice, unlike the old H.264 codec, you can compress more without sacrificing audio and video quality.

What is a codec exactly

Has it happened to you that you download a video file and then you cannot use it in your player? Or that you finally finish editing your video clip and it takes years to upload to the Internet? You might think it is a problem with your file. You are not wrong, only the question is more specific: it is about the codec and container you are using.

Maybe they are somewhat strange terms, but they are gaining more and more popularity due to the growing community in online video and audiovisual production. So if you plan to start your career as a youtuber, take into account the information, because if you end up with a final video with a weight of 1 GB it will not be fun waiting for it to go up …

What is a codec?

Those who do video editing know full well that storage space can be a problem. It is better to have the material you record in its original format, but most of the time this involves a considerable amount of GB of space. For example, if you record an hour of content with an HD camera, you may need … up to 410 GB! This is difficult to keep it, much more if you want to transmit it to other media. This is where the topic gets interesting.

The term codec refers to the video or audio compression and decompression process. It is a tool that encodes video using algorithms and converts it into information. This way you can decrease the file size.

The choice of the codec depends on different factors. You must mainly take into account the means of reproduction for the final product. However, encoding is not enough for its reproduction, it is also required to “pack” the information in order to present it. We are talking about containers.

What are those containers?

Suppose you just finished editing a video. The final file contains both images and audio, so you require a way to display it just as you prepared it. This “package” is basically what many refer to when they talk about the format of a file. So a container can accept different codecs, while players can use certain containers. For example, the VLC player accepts almost all containers.

Lossy and lossless codecs (lossy and lossless)

There are different types of compression, as we will see later. However, all of them can be divided into two categories: with or without loss. Loss of what? Quality. For example, in the case of audio files, it is not the same to listen to a song in FLAC (Free Lossless Audio Codec) format to one in MP3 (MPEG Audio Layer III). The first is coded in such a way that almost no information is lost when compressing, that is, fidelity is maintained.

The same goes for the video. Wanting to save storage space, lossy files, ie lossy, are compressed. This makes them much easier to manage. However, it is unavoidable to deal with data loss and therefore image or audio fidelity. On the other hand, when you want to maintain the highest possible quality and have no space problem, lossless or lossless compressors are used. Again, it all depends on the purpose of your file. Will it be a web video? A projection? Film contest?

Video codecs

Below you will find a list of the most popular codecs. We will not go too far into others, since an average consumer rarely requires those who are specialized.

DV and HDV

Do you remember the tapes or cassettes to record video? This type of capture uses the DV codec, the standard defined by various electronic sales companies. Over time, HDV emerged, as they had to adjust to the demand for high-definition video.

H.264 / MPEG-4 AVC

Platforms like YouTube have made the popularity of this codec grow quite a bit, as it is their recommendation to upload your videos. It is one of the most suggested thanks to the fact that it considerably reduces the file size without sacrificing much image fidelity. Multiple cameras use the codec, as do web video and Blu-ray.

Microsoft VC-1

Microsoft has its encoding mode for Blu-ray content. It also works in your Microsoft Silverlight tool.

MJPEG (Motion JPEG)

Many video cameras used to capture material with this codec. Its name comes from the group that created it, the Joint Picture Experts Group. If the name seems familiar to you, it is because they are the same ones that created the JPEG still image compression codec.

MPEG-1

Before H.264 there was MPEG-1. This used to be the standard for online video, although the emergence of new formats has left it behind.

MPEG-2

This format is merely for compressing information to DVD video.

WMV (Windows Media Video)

This is another codec that has practically disappeared. It focuses on the Microsoft family.

Audio codecs

As we mentioned before, codecs can be used with or without data loss. As for audio, there is a huge difference not only in quality (especially with good headphones), but also in the file size. Do you prefer an entire album in MP3 or a few songs in FLAC?

ACC (Advanced Audio Coding)

YouTube, Android, iOS, iTunes and more have adopted this compression method as their standard. AAC was devised as the next step for MP3, although it still has a long way to go. However, AAC tends to be of better quality. It is a lossy codec.

FLAC (Free Lossless Audio Codec)

Recommended for true audiophiles. Its development is open source and is considered a great alternative to MP3 or CD if you want to get the best possible quality. It is also recommended because it can compress a file by up to 60% without loss of information.

MP3 (MPEG-1 Audio Layer 3)

It is currently the best known format for audio. It is not of the best quality, but its compression quality is what has made it so successful. It ignores the information that corresponds to the sounds that we do not hear in our hearing range, thus eliminating “irrelevant” space. It can be reduced between 75 and 95% of the original size.

Windows Media Audio (WMA)

This is another of Microsoft’s products. It never really took off, the MP3 format took care of it. It has two versions, one with and without loss of information, although the same extension (WMA) is used for both.

Containers

You have finished editing your video. You have already chosen the codec and now you must choose the means by which you can transport and reproduce the information you have assembled. We leave you the best known. Define which one is indicated according to the purpose of your product.

ASF (Advanced Systems Format)

This is a format that belongs to the Microsoft family. Its supported file types include .asf, .wma, and .wmv. The container works well if your devices are Microsoft, but it is not well received by other systems, not to mention the loss of popularity with other containers.

AVI (Audio Video Interleave)

We have all come across this one in one or the other download. It is still in multiple instances, but don’t consider it your first (or second) option if you’re creating content.

AVCHD

This format works with the content captured with video cameras.

Flash

Adobe has its own container, which was originally created by Macromedia. Many have made it clear that it is a limited container. For example, Mozilla Firefox no longer supports such files.

MKV (Matroska Multimedia Container)

This format increasingly gains more ground thanks to its versatility. It accepts almost any audio and video codec. It also has the ability to have multiple video, audio and text channels. It is open source, so it has a generous community.

MP4

It is one of the most popular containers. It works with the H.264 codec, making it ideal for working with online audiovisual content. As for audio, it usually uses AAC or AC3 codecs. It was created by the Motion Pictures Expert Group.

MPEG and BDAV MPEG-2

Both are used for discs, the first for DVD and the second for Blu-ray. Generally the file extensions with this codec are TS, VOB, MPG and SVCD.

Quicktime

Now we see the turn of the Apple family. Part of its appeal is the separation of information into different channels (video, audio and text). It also allows for better editing of the metadata. It compares a lot with the MP4 container.