Change framerate of video file permanently?

[nothingface]

Hi guys, I have a question.

I have an mkv file (with x264 video content), with a framerate of 25fps, it has been recorded from a PAL TV source. It is a movie with an original fps of 24, but it has been sped up to 25 fps for the PAL broadcast, and it has the usual problem resulting from that process: slightly higher pitched audio, "chipmunk" voices. I can use Reclock's PAL Speeddown feature to slow it down back to 24 fps, restoring the original audio pitch, it works perfectly.

But I was wondering if it was possible to permanently alter the framerate of the file, to "bake in" the 24 fps in the file, so I wouldn't need Reclock anymore? And If it's possible, what tools do I need for altering the mkv file this way?

Any help would be appreciated.

 

[Roycal]

If you want just the movie only version with no extras, tsMuxerRGUI can change the frame rate. Under "Input" tab check the 'change fps' box and select the frame rate you want to change it to, from the drop down box.

Select 'Blu-ray disk' if you want to output a BD format. I would start off with a movie only version with just one language audio track. But changing frame rates can mess up the audio synch and would suggest starting with just Dolby AC3 movie only version before changing the frame rate. BDRebuilder can convert it to a movie only version with a single language track and re-encode the audio to AC3.

Edit. Also, BDRebuilder has a feature selection "Assume PAL Input" or something like that, there may be an option to change the frame rate that way. That might be simpler than using tsMuxerGui.

 

[nothingface]

Thanks for the suggestions, I'll try them.

 

[Roycal]

Let me know how that goes. The last time I went through that it was a major hassle. You may have to time shift the audio seperately after changing the video frame rate.

If the audio loses synch and has the exact same time length as the original, then you have to stretch or squeeze the audio to fit the new frame rate. If I'm not mistaken, TSMuxer can do that too.

The last time I went through that was with a DVD, but I thought BD's all had the same frame rate regardless of region.

If it's a PAL DVD and you want to make it compatible with NTSC, you also have to change the resolution to fit the NTSC standard since most Region 1 players won't play a PAL resolution (which is a higher res than NTSC). In the end, with a DVD and current software tools, it's hardly worth the hassle. Better off buying or renting the title in the region you want.

Correct me if I am wrong, anyone, but I thought blu ray was not region dependent regarding frame rate. 3D has higher frame rates, of course. But not a region issue.
Obvioiusly down converting a blu ray to DVD compatability could complicate the region issue, especially if the source blu ray is 3D.

 

[nothingface]

Yeah, this framerate conversion is not as trivial as I first thought, because of the audio.

You're right, on BD all regions usually have the same framerate (at least for the main movie), so this is not a problem anymore, like it was on dvd. The problem is that this film is not available on Bluray, if it was, I would buy it in a heartbeat. The only hd source I could find is a 720p h264 mkv file, captured from digital cable or sat tv (somewhere in Europe, presumably), and it is 25 fps, sadly. So that's what I have to work with.

The run length of the film is a few minutes shorter than the NTSC dvd, and the audio sounds higher pitched, like it usually does when they speed the film up from 24 fps to 25, in order to broadcast it in Europe or other PAL countries. Hopefully they didn't apply any pitch correction or other processing to the audio when they sped it up, so if I manage to slow it back down, I get back the original sound, or something close to it. It's a 2-channel AC3 track, by the way.

As for the video, all I have to do is change the fps from 25 to 24, I don't have to re-encode it or change it in any other way, so I can retain the original quailty (I hope).

 

[Roycal]

For the audio to remain in sync with the video, it will also have to stretch the audio time. If the audio iis out of sync (i.e. it will get worse near the end of the film), then you can use audacity to stretch the audio time. You can follow these steps:

First use TSMuxerGui to cut off the first and last 1 or 2 seconds of the video to make sure there is no time difference in video versus audio durations.

1. Use TSMuxerGui to demux the audio and video into seperate stream files.
2. Use TSMuxerGui to change the framerate of the video only.
3. Use Audacity to stretch the audio stream to match the new video time.
4. Use TSMuxerGui to remux the new audio and video into a single file.

If the audio is still out of synch but doesn't get worse, then you can use Audacity to trim the audio (or add quiet time) and remux again. That's where the real work can come in.

Hopefully you're right and if it's the PAL version that sounds high pitched, you probably won't have a problem with the audio.

Update: I just realized that ClownBD (not ClownBDCopier) also has a framerate change setting. Under fps selection, select "slow down". It looks much simpler than above method.