Live streaming is an exciting way to engage audiences all over the world. In fact, if you listen to the statistics, live streaming’s popularity is growing at an exponential rate. The real-time nature of live video is a huge part of the medium’s success, but it’s also part of what can make it so challenging.
From a production standpoint, you’re building the plane while it’s flying. But Vimeo Live is here to help. We’ve assembled a list of the key terms you’ll need to get your live event up and running, and keep you looking professional in the process.
Some words in this glossary might look familiar. But don’t forget, the nature of live can alter the meaning of even the most traditional aspects of filmmaking. So let’s get to it.
Live streaming: the act of streaming live video online to many viewers at once. Due to the interactivity between the viewer and broadcaster, live streaming is an entirely new storytelling medium.
Compression: with regard to live, compression increases processing efficiency, and thus decreases the overall size of the video being streamed. The industry standard is H.264 (better known as MPEG-4). Vimeo uses this compression for both our uploaded and live videos.
Encoding / transcoding: when video is first recorded it exists in one of a variety of formats, depending on your recording equipment. Encoding is the process of converting raw, analog, or broadcast video files to digital video files.
Cloud transcoding: utilizing a network to provision encoding machines the moment they are requested, as opposed to having dedicated machines waiting, unused.
Hardware encoder: a computer dedicated to encoding and processing video. Hardware encoders, like our pals at Telestream, offer optimized performance and come preloaded with broadcast software.
Software encoder: a software program that encodes and broadcasts live video. There are many types, but all are programs installed on a computer, and they can be customized based on the specifications of the machine on which they’re running.
Frames and frame rate: frames are the series of still images that make up your video. Think of these like the pages of a flipbook. The less motion per frame and the more frames per second, the smoother the video. Frames are measured in frames per second (FPS), the number of frames displayed per second of video. Frame rate directly affects compression and is one of the main factors in encoder settings. The two most common frame rates are 30fps and 60fps.
Bitrate: the rate at which the packets of data are being transported from point to point. This is typically measured in kilobytes per second, and can vary based on both source and receiver network connections, video compression, and resolution.
Streaming server: a machine that receives the stream and performs certain processes such as encoding or compression. A streaming server then transmits the packets of data to the player, where viewers can watch.
RTMP (Real Time Messaging Protocol): the media streaming protocol used for live streaming from a broadcaster to the Vimeo Live backend. Developed by Adobe, this protocol is used to transfer video over the internet. It’s the web address that provides the path for data to be passed from the broadcast software to the streaming server.
RTMPE: similar to RTMP, but different. RTMPE is the encrypted media streaming system based off RTMP.
Stream key: an alphanumeric key that allows encoding software to identify and communicate with the streaming server.
Ingest point: the point at which a streaming server begins receiving a signal from a provisioned broadcast.
Inter frame prediction: a method of video compression utilizing existing frames’ shared elements to predict and pre-load the same elements in future frames. This process greatly increases compression rates and allows us to process more video (per second) than what would otherwise be possible. Think of this as copying and pasting objects from one page to another, instead of drawing them over and over.
Key frames: also known as I-Frames, these are completely processed frames of digital video. They are the largest frames to process, since there’s no prediction used to display them. In fact, these are the base from which “delta frames” predict motion and copy objects. In encoding settings, key frame duration is an important one to consider. In general, forcing a key frame every two seconds is optimal for live streaming.
Delta frames: these are the frames that follow key frames in the group of pictures (GOP) sequence. These frames are easier for machines to process because they use prediction algorithms to pre-load where objects will be in their next frame based on information from other frames. This is the process known as “inter frame prediction.” There are two types of delta frames:
- P-frames: (predictive) frames only use elements from previous frames to predict motion of objects, and use that information as a processing short-cut.
- B-frames: (bidirectional) frames use elements from previous and upcoming frames to predict motion of objects, and use that information as a processing short-cut. These frames are more versatile than P-frames, but take slightly longer to process.
GOP (group of pictures) sequence: this is the typical structure of video frames for compression using inter frame prediction. This can vary, but the structure is usually:
I-Frame | B-Frame | B-Frame | P-Frame | B-Frame | B-Frame | P-Frame
Content delivery network (CDN): a network of global servers that allows users to access websites (which could be based anywhere) from a machine that’s geographically local. For example, if a user in Hong Kong wants to check your England-based site, they’ll automatically connect to the CDN’s machine in Hong Kong, which has a copy of all information accessible on the server in England. The CDN greatly improves network connection, and user experience, by shortening the cable run.
Chat: this feature allows viewers of a live stream to post live comments that run alongside the video player. This chat occurs in real time, and it’s an excellent way for viewers to communicate with the on-camera personnel, as well as each other. Live chat is one of the defining elements of live streaming as a medium, and is included in Vimeo Live.
Shadow ban: the process of blocking a user from the chat whereby the user can still continue to post, but none of their messages appear to any other users. This feature is to combat those who would abuse the chat, or become obstructive to the chat or the event itself.
Live support: a feature within the event setup where you can chat with a member of our support team to troubleshoot issues regarding your current setup process or event.
Simulcast: any live event that is streamed on multiple platforms simultaneously. Simulcasted live streams can include content that’s airing live on television in addition to digital platforms, or they can be exclusive to digital platforms, like Vimeo.
DVR: DVR allows live content to be played back anywhere within a predetermined timeline.
Slate: this is an image or short video clip that’s deployed in a broadcast software to “cover up” a live stream for a certain amount of time. They’re called slates because they’re the digital equivalent of the painted slates of wood used to display messages in the early days of film. Some common slate messages are “We’ll be right back,” “We are experiencing technical difficulties,” and “Thanks for watching!” While a slate is deployed, a broadcaster can be free to adjust settings, troubleshoot, or even take a restroom break without the viewers knowing. For streams simulcasted from television, slates are often used to cover up commercial breaks that are unauthorized to be streamed online.
Monitoring: watching the live stream as if you’re a member of the audience. This is usually done from the production area during streaming to be sure the event isn’t experiencing any technical problems from the viewer’s perspective. Monitors can refer to the screens themselves, as well as the people watching them.
Backhaul: content that is being recorded live, but isn’t being broadcasted. For example, if a basketball game goes to a commercial break, the cameras will continue rolling, even though the viewers are just watching commercials (or a slate). Backhaul content is seen in the producers’ software and typically not shown to viewers. If it’s live to viewers, it could indicate a technical problem in the broadcast software.
Hot mics: microphones that are live and recording while the event is on a break. Think: commentators at a sporting event talking to each other during a commercial break. This is something to watch out for, since the speakers assume they’re not live. The best way to troubleshoot here is to have your producer deploy a slate over your live stream.
Natural sound: sometimes referred to as “nat sound,” this is naturally-occurring audio. Colloquially known as white noise or background noise, natural sound is a potential obstacle in live streaming, but is fairly easy to manage. Live producers will usually listen for natural sound in their monitors before anything else to confirm that audio is being properly recorded. The wind is a good indicator of natural sound at an outdoor event, as is the dull roar of a crowd at a sporting event.
Audio visual sync: the relationship between audio and video tracks of a live broadcast. If the sync is off, either the video will be ahead of audio, or vice versa. Checking sync is important before going live, because it’s one of the most frustrating technical problems for viewers to experience during a live event.
Video artifacting: a specific type of pixelation where objects in a video appear distorted. This differs from regular pixelation because only certain objects or portions of the screen will appear pixilated, not the entire frame. Video artifacting is often indicative of a problem with compression settings.
Dropped frames: these signify the loss of video frames during the encoding/compression stage. This occurs when more data is being transferred than the machine’s CPU is able to process. This results in a live stream looking like it’s skipping, while audio falls further out of sync with each dropped frame. This usually requires restarting your machine, so having a backup machine is the best protocol. If that doesn’t work, this issue can also be that your encoder settings are incorrect.
Broadcaster: the title given to the client(s) who are delivering media to the live backend.
Fiber: a fast and reliable solution used to transmit the live stream from the event source to the encoder destination. For large scale events, live stream production crews will rent fiber in the ground. Fiber is also often used as a redundant source (with satellite) for the largest scale events.
Satellite: a fast, reliable (and expensive) solution, used to transmit the stream from the event source to the encoder destination. For large scale events, live stream production crews will rent a satellite for distribution. It’s also often used in remote locations, or as a redundant source (with fiber) for the largest scale events. Note that bad weather negatively affects the satellite’s signal strength.
Uplink: the connection from a production truck to the satellite for the master live stream.
Downlink: the connection from a satellite back to the specific encoding site or full production studio.
Delay: depending on the type of live stream, there may be an intentional delay on the production side. For example, you may want to cut out before something sensitive hits end viewers, insert lower thirds throughout the stream, or censor mature language.
Redundancy: this is a good production practice, and refers to a variety of backup techniques during a live stream.
A fully redundant live set includes backup camera feeds, backup data source streams coming out of the mixer, backup RTMP streams, backup signal types being sent, backup encoders for each master feed, backup streams or profiles for playback, and backup CDNs that each set of streams are being served from.
Lower thirds: a media term for graphical elements on the bottom of the video, which are overlaid on top of a stream through a switcher (e.g., the title of the person on camera).
Bugs: a media term that represents graphical elements, which are overlaid on top of a stream with a switcher (e.g., the logo of a brand).
IP camera: an internet protocol camera, or IP camera, is a type of digital video camera commonly employed for surveillance, which — unlike analog closed circuit television (CCTV) cameras — can send and receive data via a computer network and the internet.
Ingest: the act of consuming video that’s sent from a broadcaster in the live backend.
Chopping: the clipping of recorded live media. This is for the purpose of ending the test period at the beginning of the live stream, so that viewers don’t join the live stream in a DVR scenario.
Switcher: also known as a “video mixer” or “vision mixer,” the switcher is a device used to select between several different video sources. In some cases it can be used for compositing (mixing) video sources together to create special effects. This is traditionally hardware, but there are many software solutions coming out as well.
Wowzers! There’s a lot to take in, but you can keep referring back to this handy glossary for all things live video. If you master the terms above, you’ll have the tools and technology you need to document some show-stopping live events.
We’ll be adding lots more insight on all things live video, so keep your eyes up and ears down on our Video School blog. In the meantime, if you’ve got some live stream definitions that you are itching to share with the world, comment below and we’ll do our best to define ‘em. Maybe not at live stream speeds, but definitely at human brain speeds.