horshack Posted January 9 Share Posted January 9 I have a project where I need to precisely match the timing of video to audio. In the course of setting that up I noticed what appeared to be a fixed audio lag/skew in my S5 video. It's worst as 60p and occurs in both 1080 and 4K. I created a video to demonstrate what I'm seeing: Setup Arduino UNO R3 board running code I wrote that turns on the LED at the same time I turn on a buzzer. The LED+sound stays on for 100ms, then is turned off for 100ms. Repeats continuously. This creates 6 frames of the LED on+buzzer, then 6 frames of the LED off with no sound (for 60p recording, which is 16.66ms/frame, so 6 frames in ~100ms). S5 is configured for 4K 60p 1/250. That fast shutter speed was selected to always catch the LED turning on within a single frame. There is a lav mic into the S5 that is positioned right next to the buzzer on the Arduino. Observed Behavior I expect the video to show the LED turning on at the same time the audio waveform shows sound from the buzzer, or within 1 frame of each other, to account for any timing skew between the start of an S5 frame and the start of the LED+buzzer. Instead the S5 shows 2-3 frames of the LED on before the waveform shows sound from the buzzer, indicating that the audio is lagged/skewed by 30ms to 50ms. The lag is slightly less if I record the same setup over HDMI instead of internally. I also compare the S5 to the Sony ZV-1 recording the same setup, which shows the expected behavior of <= 1 frame lag between LED and audio. Quote Link to comment Share on other sites More sharing options...
kye Posted January 10 Share Posted January 10 2 hours ago, horshack said: I have a project where I need to precisely match the timing of video to audio. In the course of setting that up I noticed what appeared to be a fixed audio lag/skew in my S5 video. It's worst as 60p and occurs in both 1080 and 4K. I created a video to demonstrate what I'm seeing: Setup Arduino UNO R3 board running code I wrote that turns on the LED at the same time I turn on a buzzer. The LED+sound stays on for 100ms, then is turned off for 100ms. Repeats continuously. This creates 6 frames of the LED on+buzzer, then 6 frames of the LED off with no sound (for 60p recording, which is 16.66ms/frame, so 6 frames in ~100ms). S5 is configured for 4K 60p 1/250. That fast shutter speed was selected to always catch the LED turning on within a single frame. There is a lav mic into the S5 that is positioned right next to the buzzer on the Arduino. Observed Behavior I expect the video to show the LED turning on at the same time the audio waveform shows sound from the buzzer, or within 1 frame of each other, to account for any timing skew between the start of an S5 frame and the start of the LED+buzzer. Instead the S5 shows 2-3 frames of the LED on before the waveform shows sound from the buzzer, indicating that the audio is lagged/skewed by 30ms to 50ms. The lag is slightly less if I record the same setup over HDMI instead of internally. I also compare the S5 to the Sony ZV-1 recording the same setup, which shows the expected behavior of <= 1 frame lag between LED and audio. I see a delay in the audio from my GX85, and where it matters I just re-align them manually. If it matters to you, just include an event at the beginning of each clip that allows you to align it in post. This is why the clapperboard is used in making movies - it allows the picture and sound to be aligned. If it matters then you should also ensure that the timing is stable over time, so there are no drifts over long takes. Quote Link to comment Share on other sites More sharing options...
horshack Posted January 10 Author Share Posted January 10 21 minutes ago, kye said: I see a delay in the audio from my GX85, and where it matters I just re-align them manually. If it matters to you, just include an event at the beginning of each clip that allows you to align it in post. This is why the clapperboard is used in making movies - it allows the picture and sound to be aligned. If it matters then you should also ensure that the timing is stable over time, so there are no drifts over long takes. Yep, I've started using the Arduino just for that purpose, to have a precise video/audio sync lead-in. Quote Link to comment Share on other sites More sharing options...
horshack Posted January 10 Author Share Posted January 10 Follow-up. After my earlier post I've determined the issue appears specific to the AAC audio codec, which is the codec utilized for all the lower bit-rate MP4 mode files. If I switch to LPCM the issue doesn't occur - LPCM is utilized for all of the higher bit-rate MOV mode files. Here's a new video comparing the two audio codecs: sanveer and kye 1 1 Quote Link to comment Share on other sites More sharing options...
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