Audio and video synchronisation

[g3yjr]

I have video working from a PiCam and audio from a C270 Webcam, but the audio leads the video by some seconds.

Is there a setting I can tweak to get synchronisation?

Graham

[g3yjr]

I suppose one way is to input audio and video into OBS on a PC, but I want to use Portsdown4 as the DATV transciever, so is there a way to delay the audio in order to allow me to sync with video?

Graham

[g0mjw]

You could invest £3 in a USB audio dongle perhaps? I think the problem is that you are using a camera rather than an audio source. The audio dongle seems to work best with the PI camera. Note if you are using MPEG2, I found latency builds up over time at low SRs.

[g3yjr]

Mike,

Yes I'm using the audio dongle for audio out. I tried it with a mic in, but the level was way too low. I think I'll need a pre-amplifier.

I guess that is a 'no' to an adjustable sync setting?

OK re MPEG-2.

I'll try some mic amplification into the dongle.

73 Graham

[g0mjw]

I don't think there will be an adjustable offset. Not sure why the audio level would be low from the dongle but it might be the microphone perhaps. These tend to be designed for active microphones and headsets. The several seconds delay doesn't sound right but that might be because it is coming from a camera source.

If you want to adjust the delay you can but it would involve modifying a script and it would be over-written by the next update. I don't know if Dave can include an audio offset adjustment, or if there already is one in the config menus, but it is usually better to stick to the supported hardware.

Mike

[G8GKQ]

Hi Graham

You can adjust the Mic Gain for the USB Mic dongle. Menu 3, Set USB Mic Gain. Might be worth checking.

There is no easy way to adjust the Lip Sync between the Pi Cam and a C270 used as a microphone. The system is optimised for the USB audio dongle to be used with the Pi Cam.

Dave

[g3yjr]

Mike,

yes I don't really want to get into making repeat amendments to code. I use the usual Ebay white dongle for audio, plugged straight into the USB on the RasPi. For video I am using the High Quality PiCam.

The output from my mic into the audio dongle is probably quite low. Also I get plenty of mains pickup, but that has let me do a test: I get about 2.5s video delay using the Audio=USB Mic setting. (Touching the mic boosts the hum - I guess the audio dongle input screen may float, so I will try tying it to earth).

Using the C270 webcam mic and the Audio=Webcam setting, I seem to get the same delay.

Dave, thanks for the reminder about the Mic Gain setting. I've set it at 30, the maximum.

With the sync optimised for the audio dongle in the software, I'm puzzled why I get a delay. The s/w version is 2023 02 031. The voltage into the RasPi4 is 5.1V min.

Thank you for your comments.

73 Graham