Tips and Training >> Definitions >> Codec

What is a Codec?

The word Codec is a combination of two words "coder" and "decoder". A piece of each word is used to create the commonly used word “Codec”. Think of this as a coder and decoder. There are many variants of codecs and they all perform this "encode" and "decode" function with some form of compression or reduction in size of source video and/or audio.

A Codec can be software based or it can be hardware based. Coding and decoding video and audio signals is required to convert video and sound into bits of information that can be transmitted, and translated.

The H.264 codec is used in many applications from DVD's to YouTube videos. It is a standards based codec that many manufacturers have adopted and therefore with this codec, broad cross-compatibility between video enabled devices is possible. However, there are many different types of codecs including some that are only for audio.

A Codec allows the ingesting of sound and video into electronic form. That electronic form of sound and video can be transmitted, copied, moved and rendered into other forms. This means that through the use of a Codec, information as represented by sound and video can be encoded and them moved and transformed. A Codec that allows for the ingest of audio and video is “encoding” those signals into a form that can then be decoded after movement or manipulation. The decode process requires a codec also and so coder / decoder functions require devices to include codecs whether they are hardware, software or cloud based.

Why are Codecs Important?

While Codecs are often invisible to users, they are extremely important because without them video and audio conferencing would be impossible. Codecs are intended to make video and audio conferencing cross-compatible between hardware systems. However, in addition to hardware codecs that are manufactured by Polycom and Cisco Systems, many cloud based software tools also enable video conferencing. Each session of video and audio communication must invoke the use of Codecs to operate. As there are many different Codecs, each with their own method of encoding audio and video, the choice of Codec is critical to enable successful conferencing. Each cloud based platform uses its own Codec selection for its service. This can create incompatibilities.

Various providers of cloud-based video conferencing services select Codecs and manage video and audio in their own way. As such, successful interoperation between video conferencing systems and tools is not assured. Zoom, WebEx, Teams, Apple Facetime and other services use both interfaces and Codecs that may not be interoperable. Gateway services whether provided by the cloud operators or 3rd parties can work around these incompatibilities.

TKO VideoConferencing (“TKO”) is a high quality provide of video conferencing support services. The company provides gateway access portals that allow Zoom, Teams, WebEx, Polycom and Cisco systems to interoperate in video conference sessions, webcasts and for both Town Hall and All Hands Meetings. TKO manages gateway services that can support mixed Codec conferences that allow successful communication between major video conferencing platforms.

Codecs in Videoconferencing and Webcasting

When used in video communications such as video conferencing, as the name implies, a Codec (Coder/Decoder) must be at both the source and destination of a communications link. The coder encodes the signal for data transmission and the decoder converts and expands the signal into audio and video that can be played when received.

In order for two or more video conferencing systems to communicate they must negotiate their video and audio codecs at the start of the connection (video and audio are encoded using their own distinct codecs). This is done in an important process called “capabilities negotiation”. In this negotiation, video conferencing systems “agree” on the codec or codecs being used and so once that is done, the systems can exchange audio and video with agreed encoding and decoding techniques that follow the agreed Codec’s rules.

The name of the Codec is often taken from the underlying encoding method. For example, the list of codecs that follow, the underlying standard is used as the encoding / decoding method. Video codecs commonly used in video conferencing applications are: H.264, H.263+, H.263, H.261. Common audio codecs are: G.711, G.722, G.728, Siren Audio and AAC. Note that audio codecs can be embedded in the containers of video codecs such as H.264.

Does Zoom Video Conferencing use a Codec?

Yes. Zoom Video Conferencing is a cloud-based video communications service that does use codecs both to encode and to decode video and audio from cameras and microphones. When using Zoom, user devices must be enabled to allow both video and audio access for the Zoom application. Once Zoom has access to video and audio, it is the Codec’s job to turn them into a communication signal that can be interpreted by other Zoom conferencing users.

Two ways that Zoom allows users to join video conferences are through a Web based application or through an application that can be downloaded to a local computer. These two methods of joining a Zoom call use different computer, tablet or phone resources to code and decode audio and video. This means that using a Web based version of Zoom versus a downloaded application-based version of Zoom affects how the coding and decoding process is managed. Users of Zoom do not need to directly make choices about the Zoom Codecs that are used, but in choosing whether to use the Web based application versus a downloaded application, users are making a choice about which system resources are available to the codecs. This is important because encoding audio and video requires processing power and system resources.

Do Zoom Phone Callers use a Codec?

Yes. Zoom allows telephone callers to join Zoom Video Conferences. Telephones encode audio from callers into a format that can be transmitted through to other telephone callers. In addition to that telephonic encoding, Zoom’s service uses Codecs for both audio and video to create an ability for telephone callers and video conference callers to communicate in the same conference session. The audio from a telephone caller in a Zoom call is encoded by a Codec into a form that is compatible with the audio from video callers. In this way, audio from both video callers and telephone callers can be exchanged.

Does Microsoft Teams Video Conferencing use a Codec?

Yes. Teams Conferencing does use codecs both to encode and to decode video and audio from cameras and microphones. When using Teams, access to both video and audio is required at the user’s device. While video is technically optional in the video session as it can be muted, the Teams application needs access to video resources such as a webcam in order to be able to include a live video signal into the video conferencing codec. In the absence of a video signal, the application still encodes video as no data and so the video codec is still utilized by the application itself. Video conferences use both Video and Audio Codecs and so even while video is muted or unavailable at the user’s device, the Codecs in use still process video as empty.

The key point of understanding regarding Codecs is that they are part of every video conferencing session. Further, which Codecs will be used in the session are negotiated at the start of each session. So whether a user mutes their video or audio at the beginning of a session, has no direct impact on Codec selection during the meeting. Video and Audio Codecs are negotiated at the meeting start regardless of whether the sources for them are muted. This allows users to later unmute their audio and/or video and participate fully in the video conference.

Consider Codecs like boxcars on a train. Once the train is in motion, the boxcars move with the train whether they are loaded or empty. Once a video conference is in session, the Codecs move between video conferencing systems. Users can add a payload to the Codecs at any time and that is like adding Audio and Video into the boxcars of a moving train.

Does Microsoft Teams Require Phone Callers to use a Codec?

Yes. Teams phone callers are assigned an Audio Codec by the Teams application when they call into a session. No specific action is required of a Teams Audio Caller to select an Audio Codec as this is done by the Teams application. Teams use of an Audio Codec means that the sound from a telephone caller is available to a Teams session as a source that can be mixed with audio from other callers and also from video callers. Teams “mixes” all of these audio sources so all parties can talk with one another. The interaction with audio between all parties is made possible by use of Audio Codecs in the Teams session.

Does Cisco WebEx Video Conferencing use a Codec?

Yes. WebEx does use Codecs for both telephone callers and video callers into a WebEx session. WebEx uses the audio from cameras and microphones whether users are connecting from a telephone, a tablet or a computer. Just as with Zoom and Teams, when using WebEx, application access to both video and audio is required at the user’s device for them to be available in a conference session.

Video and Audio Codecs encode the video and audio signals from a user’s device and then those signals are used in the WebEx session. Audio and Video, once encoded by their respective Codecs, can be exchanged and mixed so that each session participant can either see and hear in the meeting. Through the use of Codecs, WebEx provides all meeting participants the ability to see and hear all parties in the session.

Does WebEx Require Phone Callers to use a Codec?

Yes. WebEx, automatically encodes audio from phone callers using an Audio Codec. Once encoded, this audio can be mixed with the audio that has been encoded from video conference callers so that all parties can hear one another. Just like with Zoom and Teams, the Audio Codec is automatically engaged by WebEx so telephone callers can hear and be heard in the WebEx session.

Contact TKO for help today

background