Film frame rate/ Audio sync questions

[mediaman083]

Hey all,

I'm a little confused with frame rates. I have a a frame accurate machine from moviestuff. I am aware that film is 24fps. I am exporting the file from the RetroPro software at 1:1 instead of the 17fps option. The output file when doing this plays at 29.970 fps. I am trying to pair audio with this file. I can control the speed, but the film always runs out of sync with the audio this way. Ive read some articles that mention a 2:3 pulldown might be best in my situation, but thats beyond me at this point.

I guess my questions are...

1. (Seems stupid but I want to make sure I understand) Should I be converting the 29.970 output file to 24FPS? Ive tried to do this in Sony Vegas, but ... it didn't seem to have any affect on sync, or change the length of the file. I have not yet tried this in VirtualDub.

2. Should I be doing a 2:3 pulldown? If so.. how is this done?

[jagabo]

Do not capture at 29.97 fps. Capture at the film's native frame rate -- one video frame per film frame. That is much better for filtering and cleanup. You convert the frame rate once that's done. It will not cause A/V sync errors if you do it correctly (by duplicating frames or fields).

Is your film really 24 fps? 8mm film is more like 16 to 18 fps.

[Bernix]

There is difference between 24 fps and 24000/1001, it is different thing. If you are sure with 24 and you exported it as 29.97 so this is wrong. Some frames most probably will be duplicated, and motion not so smooth.
Ad audio. Audio is independent on framerate of video. So no need to speed up/down audio.
Most common audio out of sync is because there are dropped frames during capturing. There are progressive +/- sync each minute/same amount of seconds. So more longer from start sync going worse.
I think you should export your file again at proper fps. If there is not such option something must be wrong.

Berni

[mediaman083]

Yeah this is where I get confused. This is a 16mm film. The RetroPro16 captures at 15fps in fast mode. I thought I was to be converting the film to 24fps because thats what film is shown at in theaters? I have 2 options for exporting in the RetroPro software.. 17fps video file, or a 1:1 video file.

From the RetroPro software instructions:
"You can export your video with a built-in speed of 17fps or you can export without a speed, which would put
each frame of film on a separate video frame (1:1). Then you can apply any speed you wish on your computer edit system."

I have been exporting in 1:1, which gives the output file a 29.970 fps. So I am getting 1 frame of film per 1 of video, but the audio still doesnt sync correctly when dragging the video file to match the audio. It starts fine.. then just gets more and more out of sync.

[jagabo]

You want to use 1:1 mode. Then you change the frame rate to 24 fps (or 23.976 fps) simply by changing the frame rate flag in the header (or overriding the detected source frame rate in the editor). Changing the length of the audio to match the video is trivial in any audio editor.

If you are going to a native 29.97 fps (59.94 fields per second) format like DVD you keep the base progressive frame rate but add pulldown flags to make 59.94 fields per second.

Maybe you should upload a sample of each. Something with moderate motion so it's easy to tell what's going on.

[mediaman083]

I'm confused at why you say I would need to change the audio.. rather than the frame rate or speed of the film. If I recorded the audio directly from the projector.. it would be in the correct speed right? Maybe thats where I'm going wrong.. trying to pace the video with the audio.. rather than vice versa?

Ill get to making some short videos to show the issue. Back shortly..

[manono]

I don't believe he did say you have to change the audio. You might not have to if you can find the correct framerate to match it. But if you do have to, it can be easily done.

[JVRaines]

The best way to create moving picture files from the Retro scanner is to capture uncompressed in the RetroScan application, then export PNG files (1 per frame), then compile the frames into a video file using FFmpeg. It is at the last step that you specify the appropriate frame rate — nominally 16 or 18 fps for silent films, and 24 fps for sound film. Note that some movies are shot at lower rates to save film. You have to preview in an editor or VirtualDub to find the correct rate for natural motion! If you are converting the sound separately via projector, then you must manually conform sync to the video because no camera or projector runs at a perfectly constant speed nor (usually) at the precise frame rate you specified. Or you can use MovieStuff's RetroSync Sound Module. (I have no experience with it.)

This was my workflow with the Retro-8 a couple of years ago. When I had a sound film, I first created a video file as described above. Then I ran the film through a sound projector and captured audio and video with an old MiniDV camcorder pointed at a small projection and connected by FireWire. I laid the compiled video and captured video side-by-side in the NLE, found sync points, then stretched or squeezed the audio to match. The last step was to export a WAV and then remux with the video file.

[mediaman083]

Ugh.. sorry Vegas keeps crashing when I try and render. I'm working on it.

Hey JV.. wow.. thats quite a bit more work than what I thought I would have syncing audio.

This is all super confusing for a noob like myself. Ive attached an image to try and understand a bit more. Ive set the frame rate to 23.976fps. The raw audio from the projector is longer by about 6 minutes or so. Usually what I try to do and sync it is, stretching the video speed to the end of the track to start with. Then Ill zoom in and find a sync point.. and pull the video to match the audio.. then it rolls at out of sync after about 2 or 3 minutes. Some of it could be due to a missing frame or a splice I suppose.. but I'm sure its more than that.

If I adjust the sound speed and try and trim it back to the length of the video.. well.. its obviously too fast.

Shouldn't adjusting the frame rate adjust the time of the video? It does for me in VirtualDub, but not Vegas?

I'm trying to understand guys..I swear.

[jagabo]

The video is shorter 20 percent shorter than the audio because 24 fps film was captured frame-for-frame but marked as 29.97 fps. Converting it to 23.976 fps in Vegas doesn't fix the running time, it discards 20 percent of the frames. You need to convince Vegas your video is really 24 fps. I believe you can do that by right clicking on the video in the timeline (or media assets section) and selecting Properties -- or something like that (I don't use Vegas).

For your samples, don't render in Vegas. Use a simple cut editor to extract a short section without any other changes. If your video is AVI you can use VirtualDub to do that. Just set Video -> Direct Stream Copy before marking and saving the clip. And if your video is AVI you can use AviFRate to change the frame rate of the video without otherwise touching it.

https://www.videohelp.com/software/AVIFrate

[mediaman083]

Finally! Sorry for the wait. Keep in mind this has not been touched video wise (besides changing the frame rate) as its just a test for sync.

https://drive.google.com/file/d/1jdaRn0pO5gXx3OwBM7giG-_pb-Hgrg6p/view

[jagabo]

We don't want the video after changing the frame rate. We want to see the original. Including a panning shot will help a lot too (it's easier to tell if any frames are duplicated or missing). I don't know how your frame rate got to be 24 fps (I didn't notice any duplicate film frames, the dirt was different on every frame, but there may be missing frames) but I estimate that ~23.68 fps will align the audio with the video. That doesn't correspond to any film/video standard.

[johnmeyer]

1. Retroscan captures one frame of film onto one frame of video.

2. Once you have that video, you can play it at any speed you want. Roger's software handles this, I'm sure, but you can also use AVIFrate (old, simple utility) to change the AVI header so that the video file plays at the correct speed.

3. If you want to add sound, then you must set the video to 24.00 fps, and not 23.976 (24 * 1000 / 1001). because film was timed to play at 24 fps.

4. If you want to put the video onto DVD, which is hardwired to play at 23.976 with the pulldown flag set, then you'll have to change the fps to 23.976 and use Vegas to adjust the sound slightly (make sure to use the "Elastique" setting in Vegas (you'll find it in the sound file properties -- it does a MUCH better job stretching the sound).

[jagabo]

Even if you use 24 fps for film you may have to adjust the length of the audio. Analog devices are never 100 percent perfect. So A/V sync will drift off after a while. The error might be small enough to ignore with a 5 minute cartoon.

You don't need to change the frame rate to 23.976 fps for DVD. It's possible to add pulldown flags to go directly from 24p to 29.97i (though probably not in Vegas, use DgPulldown). That way you don't have to adjust the length of the audio. On the other hand, if have to adjust the length of the audio to account for analog drift, you might as well use 23.976 fps for the video.

[JVRaines]

It's possible to add pulldown flags to go directly from 24p to 29.97i (though probably not in Vegas, use DgPulldown).

O ye of little faith. Vegas has a "DVD Architect" preset that renders MPEG-2 with pulldown flags.

[JVRaines]

Hey JV.. wow.. thats quite a bit more work than what I thought I would have syncing audio.

Yeah, I know. It was an archival project and I was after the maximum quality possible. It may help to remember that numbers like 29.97 and 23.976 are meaningless if you aren't sending this to a TV station or making a DVD. Computers can play at any frame rate, so pick the rate that the film was shot at! I assume that's 24 fps for a sound film. Don't let RetroScan force you into dumb frame rate choices.

Another thing to keep straight mentally is that the rate at which the Retro-16 scans film has nothing to do with the filmed frame rate or the frame rate of the video file you create.

[jagabo]

It's possible to add pulldown flags to go directly from 24p to 29.97i (though probably not in Vegas, use DgPulldown).

O ye of little faith. Vegas has a "DVD Architect" preset that renders MPEG-2 with pulldown flags.

But does it handle unusual pulldown patterns? 24p to 29.97i is a little different than the usual 23.976p to 29.97i.

[mediaman083]

I spent the past couple days reading carefully and I've finally figured it out. Its still not a 100% perfect match.. but doing a sync edit every 20 minutes or so is tolerable until I can get the funds for the RetroSync Sound Module, which should make life much easier. That "Elastique" option in Vegas (which I didn't even know was there at all) is a HUGE help. Thanks for explaining things so thoroughly gang. You all have been a great help!