Converting NTSC audio to PAL

[Richard Crowley]

Audio is not recorded in Frames Per Second (FPS).
Audio is recorded in “samples per second”.
The standard sample rate for video is 48,000 (“48K”) samples per second.
Whether the picture is film or video, and regardless of the frame rate of the picture.

What makes you think the audio doesn’t sync? Have you tried it? If it doesn’t sync, it is not a problem with “frame rate” as that concept does not exist in audio.

[Andrew Rendell]

Actually, I have seen an NLE get confused by applying a frame rate to an audio track and therefore trying to speed it up to match the frame rate of the video. FCP, if I remember correctly. But that was because of the default frame rate in the setup for the software not matching the camera/sequence rate, not a setting in the audio file, and was easily fixed once it was spotted, so that might be worth checking. Other than that as long as it’s 48kHz it should sync for clips up to a few minutes long (for very long recordings the audio recorder has to be locked to the same sync source as the camera(s) to be sure).

[Kris Ham]

Thanks for your reply. Yes, you’re correct – I’m using FCP and it is referring to the sample rate as a 24 TC rate. The camera was set at 48kHz/24-bit, as was the H4N. My FCP settings are 25p 48 kHz, I start to get audio drift around the 1 minute mark, it’s a 13 minute clip.

I know I’m probably not using the right lingo, but to your knowledge, is there anything I can do with the audio I have to convert it to a 25 fps rate?

[Richard Crowley]

You say “I have audio recorded on an H4N (24 fps)…”
What does that MEAN exaxtly? The only choice you have when recording on H4n, is either 44.1 KHz or 48 KHz. How do you “record at 24 FPS”? What does that MEAN?

So did you record at 44.1 KHz or did you record at 48 KHz? Those are your only two choices. There is no FPS here.

Have you done this before? Did it work before and now it doesn’t?

What does “audio drift around the 1 minute mark” mean? How MUCH is the drift? Is the drift constant as you go through the 13 minutes?

Are you aware that drift over several minutes is normal for low-end pro-sumer gear like the H4n and typical DSLR cameras?

[Kris Ham]

“The camera was set at 48kHz/24-bit, as was the H4N.” <—- That is what I MEAN. 48 kHz/24 bit was the setting on the H4N.

Below is a screenshot of the audio settings, notice the TC Rate is 24 here:

And these are the settings of my VIDEO, the TC Rate is 25 here:

At the 1 minute mark it begins to drift slightly, and then is about 7 seconds off by the end of the 13 minute clip. I’m not sure how else to describe this to you.

I am not shooting with a DSLR, I shot on a Canon C100. The Canon was bought in Australia and the settings cannot be changed to shoot in 24 fps or any other NTSC format. I have not tried to sync audio with this camera previously.

[Richard Crowley]

“TC” would appear to refer to timecode which you are not using. So that seems like a red-herring.

7 seconds of drift over 13 minutes is not abnormal for gear as you are using. You can’t expect to have better sync than that for low-end consumer gear which is not gen-locked together. This is a 1.6% error. You are not the first to complain about speed error in prosumer gear.

The difference between 25 FPS and 24 FPS is 4.2% which is enormously greater than what you are seeing. IMHO this proves rather conclusively that this has nothing to do with FPS.

Simply pull up the video to match the audio wherever there is a video edit point. Surely you are not using the entire 13 minute video clip without edits.

[Kris Ham]

Thanks for your response. From what I’ve read from people complaining about H4N drift online, it seems to be no more than a 7-frame drift in most cases, and that is around the 10th minute. I’m seeing significant drift at minute 1.

The clip is a 13-minute interview that does not require cuts, and I have several others of a similar length to sync up. I’d rather not have to go through the entire project cutting at :45 second intervals and re-syncing. I’ll do what I have to do, but surely if I’m not the first person to experience this, there must be a work around with timeline settings.

If anyone out there has a solution, I am all ears!

[Richard Crowley]

Your drift is not unusual for gear of that caliber. You get what you pay for.

You can try simply dragging the length of the video to match the audio (or vice-versa). You might get lucky.

A 13-minute long interview with no cuts may be a good candidate for a non-habit-forming sleeping-aid.

[Bouke Vahl]

This is probably a FCP error, as the file is a BWF file and FCP is notirious bad with those.

Export it any way you can (QT pro, any sound editor) to plain Wave or AIFF, and import it in FCP again. (Make sure it has another name).
Chances are big your problems go away.

Bouke

https://www.videotoolshed.com/
smart tools for video pros

[John Fishback]

Some recorders place the camera’s frame rate in the metadata which can confuse NLEs. Jeremy Garchow had a way around this when it cropped up in Legacy FCP. It’s bee a while and I don’t remember the details, but you might find it by searching the COW. Sound Devices has a free download of Wave Agent which allows you to change the metadata. This might also help out.