That’s the delay we’re looking to measure.įinally at only £2 this app is cheap enough that EVERYONE who’s likely to be at the remote end of a contribution link can have it on their phone or tablet by default, so the chances of finding someone to hold it up in front of the camera are much higher. This got me thinking - if all copies of the app are in sync, then that means that a copy at each end of a contribution link are in sync at the moment the video is capured, but by the time that video frame as travelled over the link it will be frozen in time and will be very slightly in the past. Secondly it synchronises over the internet to a Network Time server using the NTP protocol so you know that all running copies of the app are exactly in sync down to some ridiculous level of accuracy. So first of all it’s a nice clock app that emulates some of the iconic clocks found in radio studios and TV galleries around the world - you know, the one with the digits AND the analogue sweeping LED display? No? OK. It costs £2 and is developed by Markus Gömmel Read on, however, to find out how you can measure lipsync in a bit more of a rough and ready way (albeit to within 1/60th of a second accuracy) using ONLY an iOS app!ĬAVEAT: these techniques are a lot better than just trying to ‘eyeball’ things, but they do not replace a proper professional tool if you are doing this for real for big broadcast uses. They work very well but they are very expensive (The one linked is over £200) so their use is limited to expensive broadcast setups and it’s impractical to ensure that everyone at the end of a contribution link has one. There are professional broadcast products that are designed to measure lip-sync. Lipsync is exactly what you would expect - when someone talks in vision is the audio in sync with the video? Do their lips move at the right time? It’s very off-putting to watch when the lipsync is out so having an easy way to check it is very helpful. That’s how you avoid those long pauses at the start of live contributions. It’s useful to know this for lots of reasons but mainly so you can accurately predict when to cue someone in if they are contributing to a live programme. Sometimes it’s referred to as ‘glass-to-glass delay’ where the glass in question is the camera lens at one end and the monitor you are viewing at the other. In this context Latency means how long it takes for your audio and video to get compressed, encoded, travel from sending end to receiving end and the get decoded and de-compressed to be displayed on a screen or PC monitor or mobile device. If you work on any kind of broadcast contribution path or live web streaming at some point you are going to want to check both latency and lip-sync. Need to measure latency and lip-sync? There’s now an App for that!
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