Video · Practical guide
Audio and video out of sync at events: IMAG, recording and streaming
If sound and picture arrive at different times, first identify where you notice it: on the room screen, in a recording or on the live stream. Compare those paths during rehearsal with the video and audio crews. IMAG is the live camera image shown on the venue's screens.
Identify the destination and viewing position
Ask which part of the program was affected and what the person was watching and hearing. In the room, record their position too. Keep observations of the stage, screen and recorded file separate so the crew can repeat that part of the rehearsal.
Use the same content marker for comparisons. The time someone opened the stream is useful context, but it does not identify the same moment within the program.
| Destination | What to compare | What to record |
|---|---|---|
| Room screen / IMAG | Person on stage, screen image and sound at the observation position | Camera, path to the screen and observer's position |
| Local recording | Visible and audible reference in the file that was actually recorded | File name, recorded signal and point checked |
| Remote reception | Picture and sound within the same playback | Link, device, connection and content marker |
Test every camera against the same reference
With the audio lead, prepare a reference that can be seen and heard during rehearsal. A hand clap can work: note which microphone captures it and which camera shows the gesture. It helps reveal an offset but does not replace a calibrated measurement.
If the cameras share one voice mix, switch through them and record the cuts. If one is in sync and another is not, keep both samples before compensating that mix. Repeat the test with the clips and remote contributors planned for the event.
To compare IMAG, you can frame the actual gesture and its image on the screen in the same shot. Label and save the clip: it helps show the difference without assigning a precise measurement to it.
Compare the start with a later section
Record the reference at the start, later on and after planned routing changes. Note whether the offset appears steady, grows or changes after a cut. That description helps choose the next test; it does not establish the cause yet.
For comparisons between the recording and remote reception, see OBS and Sync Offset (Spanish). If you are combining independent recordings, also check a recording that starts in sync but drifts later (Spanish). Keep the original files and the settings used for each sample.
ATEM Mini Pro: identify the input carrying the voice
If the microphone feeds Mic1/Mic2 and the sound arrives before the picture, check the ATEM Mini Pro analog audio delay (Spanish). Measure the offset and compare another recording. Save the setting together with the event's video format.
vMix 29: check the shared voice input
If several cameras share a voice mix, record the camera cuts. In vMix 29, check the input Delay (Spanish) for the input carrying that voice. When testing compensation, repeat the cuts and compare the recording with remote reception.
SX40/S8: check which part of the path ULL covers
If you use an SX40/S8, check the ULL requirements (Spanish). Prepare the source and canvas before testing. The documented path starts at the processor; the camera and switcher are outside that figure.
Check the result after an adjustment
Save the previous setting and the adjustment tested. Repeat the same sequence and check voice, picture and reference markers at each destination. If one camera improves while another gets worse, record both observations before deciding what to do next.
If an equipment detail is missing or a path remains untested, note what needs checking and who will check it. Associate the agreed setting with the model, format and signal path tested so it can be reproduced later.
Bring the samples and worksheet to the technical meeting
Complete the sync section of the signal worksheet: camera, destination, sample, adjustment and result. Include the conference signal map with the equipment and paths you will actually use.
To review the design with GLMedia, send the program, venue, plans, models and samples. See video processing, cameras and streaming and audio systems for the paths that need coordination.
Frequently asked questions
Does a delayed live stream mean picture and sound are out of sync?
Not necessarily. Compare picture and sound within the same playback to assess sync. Separately note how much later that program moment arrives compared with the room: that comparison concerns live-stream delay.
Is testing sync on one camera enough?
Test all planned cameras and sources. If they share a voice mix, save a sample of each camera cut before compensating the mix. One camera may be in sync while another remains offset; keep both samples for comparison.
What should I check if picture and sound start in sync but drift later?
Compare a visible and audible reference at the beginning and later on. Note whether the gap increases or changes after a cut or routing change. If you are working with independent recordings, also follow the section on a take that starts in sync but drifts later in the recording guide.
Is a hand clap enough to sign off the setup?
It provides a diagnostic sample. To complete the rehearsal, test voices, camera cuts and clips from the actual program, and check every intended destination. A hand clap alone leaves those checks outstanding.
What should I send GLMedia for a sync review?
Send the program, plan, equipment models, signal paths, labeled samples and the position where the issue was observed. Include the worksheet with confirmed information and outstanding checks.
Does the ATEM Mini Pro analog delay apply to HDMI audio?
The documented procedure applies to the analog Mic1/Mic2 inputs. Identify how the voice enters the system before choosing an adjustment; this procedure does not document compensation for HDMI audio.
In vMix 29, should I check Default Input Audio Delay or the input's Delay?
For the voice input in use, check General → Delay in its settings. Default Input Audio Delay sets the value for new inputs. Save the previous setting and, after testing a change, compare camera cuts, the recorded file and remote reception.
Does Tessera SX40/S8 ULL measure latency from the camera to the LED wall?
The specification covers the path from the processor input to the LED. To assess latency in your setup, also test the camera, switcher and other upstream stages.