Audio out of sync (FCP)

I broadcasted a live show on the internet (Boinxtv-CamTwist-FlashMediaLiveEncoder-Ustream), it went really well. The English show last 2hours.
I used 2 Panasonic AGDVX-100B on a new MacBookPro 17inch with express card (Too slow, I will return it to Apple tomorow).
We recorded the audio for rebroadcast. I didn’t change any preference, so the format was Apple Intermediate Codec at 24 FPS.
I converted the video file into pro res 422LT with MPEG Streamclip to work better in final cut.

I am trying to sync the mixed audio to the recorded show in final cut. The begining is sync but after 25 minutes, the is almost 2-3 sec of delay between the audio and the video!

I tried reconverted the video source (Apple Intermediate Codec) in pro res with quick time 7 (pro) and it’s the same problem!

For now I manage to change the speed of the audio to make it match (not perfect but it’s better).

May be next time I should record directly in apple pro res? Or should I broadcast 30FPS? I don’t know?

Can anyone help me with this? thanks

Make sure you use the latest version of BoinxTV. In 1.8 I think, we had the issue that at 24fps an AV sync issue may appear. With 1.8.1 this glitch was fixed.

But there is another thing you should try: Open the application “Audio/Midi Setup” in /Applications/Utilities/. Select the playthrough device you are using in BoinxTV (e.g. “Soundflower 2ch” if you are streaming). Note the Format/Sampling rate of the device on the “Output” tab ( Now select your input device (e.g. a Mixer, audio interface or microphone) and adjust the Format/Sampling rate on the input tab to the same rate as the output rate of the playthrough device ( If it is not possible to adjust the input device, simply adjust the playthrough device to match the input device. As soon as the two devices match, start BoinxTV and record. That should solve all A/V sync issues.

Hi Bastian

Thanks for your help, l ran some test on my Imac and it worked well, no problem before the show, the sync was good.

During the show, the audio feed in the built in input was 44Khz, I didn’t check the settings ( from the macbook pro 17inch 2.3GHz), thinking It was OK. I retruned the macbook pro to apple because the percentage was 400%… Next time I will get the macpro!

I recorded the first show (English 120min) in Boinx tv (30fps this time in apple intermediate codec), Everything went well except the high %. I didn’t have time to convert for final cut in boinx tv because the next show was 30minutes after. I also recorded the second show and after convert for final cut by boinx tv.

After I tried to convert the first show with boinx tv but I coudn’t select the first show. So I converted it with compressor into Apple Intermediate Codec with AAC audio at 48kHz.

The first show in final cut pro, I had to change the speed 99.9% to sync the audio remixed with the video exported. The audio didn’t match (44 vs 48 Khz).

I didn’t need to change the speed to sync the second show (converted in FCP codec by Boinx tv)

Question 1) Is there a good way to convert with boinx tv into a codec that will work with Final Cut Pro even if you didn’t converted it at first. Is there a way to do it later?

Question 2) Is there a way to put the show on a 2nd and also 3rd screen? The 1st screen is for the mixer (preview etc), the second screen is for the live screen. And I would like to use a 3rd screen also with the live screen.

Question 3) Is it possible to put on a 3rd screen only few layer preselected.

  1. Normally if you record to AIC, you don’t have to convert for FCP. It won’t hurt though. If you simply drop the BoinxTV recording into a blank FCP Sequence, FCP will ask you if it should match the Sequence settings to the movie. Click yes and you can start editing it. Conversion is only necessary if you need to match a specific setting. In FCPX you don’t have to worry at all. FCPX will take care of that for you.

  2. A 2nd screen isn’t a problem, You can either use fullscreen playout our pop put the preview windows. A 3rd screen is an issue as this has to be on another graphics card, to display there, huge amount of video data need to be copied through the data bus, as graphics card cant communicate directly. This creates a bottleneck and most of the times a serious performance issue.

  3. See 2)

1)Putting the AIC into FCP works OK, but I have a sync problem (I have to change the speed of the audio to 99.9%)! When I convert for FCP, it worked without changing the speed of the audio (to solve the sync problem) with the 2nd show!

Is there a way for boinx tv to convert the AIC video for FCP afterward to avoid sync problem?

On our set, there is a TV that shows the preview so the guys who are interviewed, can watch when we present a video (prerecorded), but I don’t want them to look at theTV and be disturbed by themselves during the interview… SO we put a piece of cardboard in front of the TV and remove it when it’s time to see a short video. I wanted to know if there is a way with boinx tv to make sure they only see the videos but on internet broadcast the show?


You can do a custom QuickTime export from the export sheet, simply Adjust it to your needs (could even be ProRes 422) and use this export instead of the Built in FCP Export.

There is no such functionality that would allow for that.