30 fps to 24 fps

[tck444]

I have seen numerous videos about shooting at higher frame rate and playing back slower to create a smooth video. So, I shoot at 30 fps then render the video at 24 fps. The video looks exactly the same, runs the same length of time, and has exactly the same file size. Just wondering what I am missing here ?

Using Pinnacle Studio 22.

Comments and suggestions appreciated!

 

[Tufargon]

The higher the frame rate the better it will look when the "video is slowed down".

 

[tck444]

Yes, that was my thought also. I was expecting the video to produce a bit of slowed motion (or have longer running time ). But, seems exactly the same visually.

 

[Tufargon]

If it's running the same time then you didn't slow it down. Edit the video to play half speed.

 

[SmilingOgre]

I've read a lot on using unmatched frame rates and a lot of writings that claimed it is jittery, etc. I don't see it either. I use Premiere Pro and as far as I can tell the program takes care of it. I mix 24 and 25 a lot as I have EU spec camcorder. Maybe I'm just not an expert viewer. I have no idea.

 

[brett8883]

I have seen numerous videos about shooting at higher frame rate and playing back slower to create a smooth video. So, I shoot at 30 fps then render the video at 24 fps. The video looks exactly the same, runs the same length of time, and has exactly the same file size. Just wondering what I am missing here ?

Using Pinnacle Studio 22.

Comments and suggestions appreciated!

You would have to interpret the video as 24 frames per second for this to work. You want to play back all the frames just at a slower speed.

Alternatively you could put the video on a 24 FPS timeline and slow down the video to 80% speed (20% slower)

Basically what this does is use a small amount of slow motion to make the video smoother but not so slow that it makes the video look weird and you don’t lose any quality because you are using a lower frame rate.

I have example of this. This first video is the original shot at 30 FPS and played back at 30 FPS.

Then this is the same video played back at 24 FPS (or slowed down by 20% on a 24 FPS timeline if that’s easier to understand)

If you are viewing the forum from a computer you can press play on both videos at the same time to watch then side by side to see the difference

 

[brett8883]

When you export a 30 FPS timeline to 24 FPS you are just dropping frames you aren’t slowing the playback speed.

 

[brett8883]

Keep in mind the special sauce here is to slow down by EXACTLY 20% and use an EXACTLY 24 FPS timeline when working with footage shot at 30 FPS. Basically the stars align at that speed and frames rates where 24 FPS is exactly 80% of 30 (so you don’t lose any frames or have to interpolate any frames,) 24 FPS is a widely accepted playback speed, and 20% slower footage is perfectly slow enough to be noticeably smoother but fast enough that it doesn’t seem like slow motion.

 

[SmilingOgre]

You would have to interpret the video as 24 frames per second for this to work. You want to play back all the frames just at a slower speed.

Alternatively you could put the video on a 24 FPS timeline and slow down the video to 80% speed (20% slower)

Basically what this does is use a small amount of slow motion to make the video smoother but not so slow that it makes the video look weird and you don’t lose any quality because you are using a lower frame rate.

I have example of this. This first video is the original shot at 30 FPS and played back at 30 FPS.

Then this is the same video played back at 24 FPS (or slowed down by 20% on a 24 FPS timeline if that’s easier to understand)

If you are viewing the forum from a computer you can press play on both videos at the same time to watch then side by side to see the difference

Doesn't Premiere Pro do that automatically? I've stacked 24 and 25 for 15 minutes or more, synced the two with audio and get what I perceive as perfect results.

 

[anotherlab]

Doesn't Premiere Pro do that automatically? I've stacked 24 and 25 for 15 minutes or more, synced the two with audio and get what I perceive as perfect results.

When you export out a video at a different frame rate with Adobe Premiere (or other NLE tooling), the export process may either drop frames or generate new frames by interpolation. No matter how you do it, when you go from a slower frame rate to a faster one, you are creating new information. When you go from faster to slower, you are discarding information.

 

[brett8883]

Doesn't Premiere Pro do that automatically? I've stacked 24 and 25 for 15 minutes or more, synced the two with audio and get what I perceive as perfect results.

No, Premier Pro will not change the playback speed of your video unless you tell it to. If you have a clip that doesn’t match the timeline frame rate Premier Pro will drop frames from the higher frame rate videos to match the timeline or interpolate frames to match the time line. So if you put the 25 FPS video on the 24 FPS timeline it will drop 1 frame per second from the 25 FPS video.

If you’d like to change this you can right click on the video and go to properties and “interpret video” and then change the frame rate of the video to your timeline frame rate. This would make a 25 FPS video on a 24 FPS timeline 4% longer but no dropped frames. Probably unnoticeable either way, however.

 

[Tufargon]

Thanks Brett8883. I've been following the thread and I appreciate your knowledge on the subject.

 

[Olav van Gerven]

I shoot at 50 fps and edit in 25 fps. The advantage is, that I can fly with higher speed and get more footage, which I slow down as I need it to. Gives me more opportunities to play with the footage.

Since most of my (drone)footage is used for youtube, I normally even edit in 1080i, recording in 2K (Mavic Air), then gives me the chance to zoom in without loosing to much quality.

 

[Drumsagard]

I shoot at 50 fps and edit in 25 fps. The advantage is, that I can fly with higher speed and get more footage, which I slow down as I need it to. Gives me more opportunities to play with the footage.

Since most of my (drone)footage is used for youtube, I normally even edit in 1080i, recording in 2K (Mavic Air), then gives me the chance to zoom in without loosing to much quality.

I do exactly the same and it does look very smooth when slowed down.

 

[Thmoore]

This is great information, thank you for it!

 

[SmilingOgre]

When you export out a video at a different frame rate with Adobe Premiere (or other NLE tooling), the export process may either drop frames or generate new frames by interpolation. No matter how you do it, when you go from a slower frame rate to a faster one, you are creating new information. When you go from faster to slower, you are discarding information.

No, Premier Pro will not change the playback speed of your video unless you tell it to. If you have a clip that doesn’t match the timeline frame rate Premier Pro will drop frames from the higher frame rate videos to match the timeline or interpolate frames to match the time line. So if you put the 25 FPS video on the 24 FPS timeline it will drop 1 frame per second from the 25 FPS video.

If you’d like to change this you can right click on the video and go to properties and “interpret video” and then change the frame rate of the video to your timeline frame rate. This would make a 25 FPS video on a 24 FPS timeline 4% longer but no dropped frames. Probably unnoticeable either way, however.

Thanks guys! Always wondered about that because I could not detect the dropped or duplicated frames watching the finished video. Pretty amazing stuff.

 

[Dave Maine]

When slowing footage down on a timeline from either 60 or 30 to 24 FPS, there is no integer relationship between the frame rates. What results is a staccato pattern of skipped frames that ends up in the final output video. Depending on the movements in the original shooting, this can be bothersome. Final Cut Pro (and Premiera and Resolve?) probably allow for more sophisticated speed changes.

The first is to create the non interger frames by averaging between the 2 nearest frames. This works well in most cases, and is fast. The best method is optical flow, which maps the motion path of every pixel and creates the needed new frames from these interpretations. This is very time intensive to produce, but can give results that are the best in some cases.

 

[brett8883]

When slowing footage down on a timeline from either 60 or 30 to 24 FPS, there is no integer relationship between the frame rates. What results is a staccato pattern of skipped frames that ends up in the final output video. Depending on the movements in the original shooting, this can be bothersome. Final Cut Pro (and Premiera and Resolve?) probably allow for more sophisticated speed changes.

The first is to create the non interger frames by averaging between the 2 nearest frames. This works well in most cases, and is fast. The best method is optical flow, which maps the motion path of every pixel and creates the needed new frames from these interpretations. This is very time intensive to produce, but can give results that are the best in some cases.

Not if you slow down by 20% in the case of 30 to 24 frames or 40% in the case of 60 to 24. You don’t lose any frames or need to create new ones.

 

[anotherlab]

Not if you slow down by 20% in the case of 30 to 24 frames or 40% in the case of 60 to 24. You don’t lose any frames or need to create new ones.

Frame rate and playback speed are two different things. If you play a clip recorded at 30 FPS at at 24 FSP, then you are slowing it down and the number of frames has changed. If you convert a 30 SPF clip to 24 FPS, you are dropping 6 frames per second. With good interpolation, that conversion can look seamless, but you have still lost information.

Another way to look at this:
If you have an 800x600 image and you want to show it on a 640x480 display, you have 2 basic ways of doing so. You can display it without scaling. You won't lose any detail, but you won't see the entire image on the screen. If you scale the image from 800x600 to 640x480, the scaling algorithms are very good and it will look pretty good. But 640 is not a multiple of 800, those pixels are going to interpolated. You will lose information by scaling,

 

[Dave Maine]

You are correct about these %. The complete table of available % possibilities follows: