Converting 50p to 59.94p (60p) using Vegas and Twixtor

PeterDuke wrote on 1/4/2019, 6:04 AM

I need to create an NTSC DVD for my friends in USA from a PAL BD project that I have just completed, because they do not have a BD player and their DVD player is NTSC only. I could have done this in Vegas alone using frame blending to change the frame rate, but I preferred to use Twixtor, hoping to get better quality. Unfortunately the only tutorials I could find on changing frame rate with Twixtor used After Effects or another video editor I did not have as the host. Searching the web was problematic because many sites said that they were changing the frame rate when they were actually changing the playback speed with the same output frame rate. I therefore experimented to find my own method (probably based on what I have read in the past) and am now submitting it to find if there is an easier or better way.

My project has a myriad of little 50p clips and 14 chapters, so I chose to work on each chapter separately to make the project manageable, rather than work on each clip in isolation or on the project as a whole. (I find that a Vegas project with many hundreds of clips can be unstable.) I therefore rendered out the video of a chapter as a 50p AVI file (Lagarith lossless). I then loaded this video into a new 50p Vegas project and applied Twixtor, with the speed set to 50/59.94 = 83.417%. I made sure the clip properties in Vegas were set to loop and then stretched the clip so that is was about 20% longer. I then looked for the loop-back point on the timeline by stepping along a frame at a time, and set the final clip length to that point. I then rendered the video out again as a 50p video. It now had the required frames for a 60p video, so I used AVIFrate to change the frame rate in the header to 60000/1001. (I couldn't get the GUI versions to work so I used the cmd version).

A problem with using Twixtor on a chapter at a time rather than a clip at a time is that the interpolation at hard clip joins produces one or two ugly frames at each join. I therefore took my original project and set the frame rate to 59.94. I then inserted a new video track immediately above the old video track and loaded in my new AVI video. At each join between clips in the source video, I stepped back and forth looking for ugly frames and cut them out, so that the original frames showed instead.

Is there an easier or better way to convert 50 to 59.94 fps?

I will be away for about a week so won't be able to respond to replies in that time.

Comments

Dexcon wrote on 1/4/2019, 6:21 AM

Have a look at DaVinci Resolve (free). With the latest build (15.2), its the best I've found so far for converting frame rates especially when using Optical Flow in the render settings.

klt wrote on 1/4/2019, 7:05 AM

Do you have 50p source, and want an NTSC DVD well playable in the USA?

I'd go the reverse way usually PAL TV stations go for a 24p movie.

They simply speed up the 24p to 25p so that the movie plays a little bit faster. This speed up is unnoticeable by watchig, but all the frames of the movie are played as original.

So I'd choose the reverse way: if your clips are really 50p, throw the half of them away, this results in a 25p movie. Then slow this down to 23.976 (aka 24p).

That's still not 29.97, but you can render this to NTSC DVD invoking 3:2 telecine. I think this will come to the closest to your original PAL movie on an NTSC DVD.

PeterDuke wrote on 1/12/2019, 4:06 PM

Thanks for the comments. I will try them out.

Musicvid wrote on 1/12/2019, 6:51 PM

They simply speed up the 24p to 25p so that the movie plays a little bit faster.

That isn't necessarily correct. Many are simply flagged as 25i; the original 24p footage remaining unaltered on the disc. Same is true for NTSC movies, and the native frame rate can be encoded with a tool like Handbrake.

wwaag wrote on 1/12/2019, 10:06 PM

@PeterDuke

You could also try the RenderPlus tool in Happy Otter Scripts which supports frame rate changes during final render. Changes in frame rate are accomplished through use of the motion vector tools plug-in to Avisynth. Here is a screenshot of the dialog and the various Avisynth filtering options.

More information can be found at https://tools4vegas.com/ and this thread https://www.vegascreativesoftware.info/us/forum/happy-otter-scripts-for-vegas-pro--113922/

PeterDuke wrote on 1/19/2019, 9:19 PM

I found a problem with Twixtor. It does not generate the correct number of frames according to the rate parameter. For instance, a 50p video with 28757 frames and a rate of 83.417% (for 59.94p output) should give 34474 frames (to the nearest whole frame). Instead it produces 6 more frames. I tried experimenting with the rate parameter, but the output number of frames varied in unpredictable steps. Unfortunately the point that I was looking for had an exceptionally high step. Rate values from 83.436% to 83.447% gave 34476 frames but 83.448% gave 34464. I have referred the problem to the makers, but no reply yet.

I had a look at DaVinci Resolve and got an error when trying to run it. A web search revealed some posts that suggested that I might need new graphics drivers, un update to OpenCL or a new graphics card with required capabilities. I have enough trouble with Windows 10 updates to spend time on researching that for the moment.

I don't fancy throwing away half my frames to convert my video, so I rule out that approach. I don't appreciate the so-called "film" look over the so-called "soap opera" look. I suppose that is because I was never a film buff.

That leaves AVISynth. People are still playing with that (e.g. FrameRateConverter by MysteryX) and building on the work of John Meyer and other giants. I will go down this path if I can't force Twixtor into submission.

Thanks to those who have replied

wwaag wrote on 1/19/2019, 9:33 PM

@PeterDuke

"That leaves AVISynth. People are still playing with that (e.g. FrameRateConverter by MysteryX) and building on the work of John Meyer and other giants."

I might add that the Avisynth frame rate converter in HOS is based almost entirely on JM's work. The only advantage is a nice GUI and easy integration with Vegas.