Audio Out Timing

There is a Sony A7xxx menu item called "Audio Out Timing," which is poorly described in the manual and on the internet. There are two choices - Live, and Lip Sync.

There is a slight delay in the viewfinder or monitor Video, of approximately 1/15 second (2 frames at 30 fps). this is probably due to processing, and is nearly universal in video cameras too. If you record externally, you must select the Lip Sync mode.

• In the Live mode, the audio is sent without a delay, so that you can listen over headphones and watch the action and listen to any bleed sound without a delay or echo (flam) effect. If you record audio/video externally via the HDMI port, the sound will precede the video by 1/15". Recordings made internally are exactly synchronized regardless of the Audio Out Timing mode.
   
   
  
• In the Lip Sync mode, the audio is delayed so that it matches the display, and incidentally, the HDMI video signal. That way you can record to an external device in perfect sync.
  

I noticed this while recording a string ensemble, using a Ninja Inferno recorder. On review, there was an almost indiscernible delay from the audio to the strings and fingers. 1/15 second is not very long, but to a trained musician, hundredths of a second are important. I shot a short video of an electronic metronome, and played it back one frame at a time. The lag was clearly visible and quantifiable, well outside the normal tolerance of the nearest frame.

There is no comparable option in the video cameras I use. The audio is perfectly synchronized with the video, for both internal and external recording.

Thanks for that info Ed.

I assume the same applies to sound captured from an external source and plugged into the camera line/ext socket?

I'm not sure it's even an issue for anyone doing 'serious' music or sound track recording though. I imagine they'll be recording wild sound into something with decent quality, rather than the noisy camera input. Then lip-synching in post.

I've never remarked whether natural, distance-induced, delay is noticeable with telephoto 'closeups'. 1/15" is equivalent to a 23 metre distance delay, which would be about right for an auditorium-based mic and camera recording the back row of an orchestra. And since that's where the percussion usually is, a drum strike could easily show that much delay.

Funny how we accept such phenomena in real life, but not on the screen.

I assume the same applies to sound captured from an external source and plugged into the camera line/ext socket?

It does, but the purpose of the Live setting seems to be unique to Sony, and perhaps other hybrid video cameras. I find it useful to monitor the sound in real time, but can ignore even a substantial delay, for example imposed by BlueTooth.

Percussionists in a classical ensemble stand at the back (20.-25'), and are trained to anticipate the beat so that the sound reaches the conductor at the right time. It is possible to insert delays when recording so that mics in the back are synchronized with those in front. I don't bother because my miking is thin enough that bleed and cancellation are negligible. I can easily add delay in post (1 mic/channel).

I record audio separately, and synchronize in post using the video sound track as a guide. Audio lag is usually less than one frame (30 fps), which is as close as you can edit anyway.