I guess I will try the PAL-discs now, since they have a professionally done 25 FPS, which is present uniform and throughout. Perhaps that will work.
I did this earlier this year with the PAL DVD releases of Stargate SG-1 seasons 1-7 and Dark Angel seasons 1 and 2 (the NTSC Dark Angel discs are 4:3, only PAL got a widescreen release). I wanted to have higher resolution copies of both, but I couldn’t put up with PAL speedup. It took a few months of poking and prodding at it before I settled down into a workflow and I got it all done early in the pandemic, as it proved to be a good quarantine project. This is what I did:
- Ripped disc with MakeMKV
- Disassembled MKVs into components with MKVCleaver and MKVToolNix. The latter program is used to take apart the audio and chapter files, and can export the video file itself at 24000/1001p. MKVCleaver is for the subtitles, as it can export them as idx/subs.
- Using MKVToolNix, took the chapter files and convert timing by applying a conversion factor to the start and end times. This is also when I go in and add the chapter titles if available.
- Loaded each file in Audacity, changing the speed under effects -> change speed. I used a .959 value for it. You then save in the highest quality you want and take care to preserve the channels, since it won’t save 5.1 properly by default.
- Using VobSub Sub File Cutter, loaded the .sub subtitles and used it to modify the timing.
- Opened up MKVToolNix and used it to -re-assemble all of the components.
- Used Handbrake to reencode the whole thing into whatever format desired. I used x265 at high bitrate for the video and audio and got good results.
This worked for me. There are probably easier ways to do it, but I had decent success with the two programs. I still have all of the seasons I did at their step 6 pre-encoding stage (usually a couple gigs an episode), if someone wants to do something similar to this with them as I lack the processing power to upscale more than short clips.
You could try using meGui for the audio. It offers options to change fps of the audio (although calling it fps is not quite true, but makes it easier to work) with or without pitch correction.
Standard changes that are possible are speed ups (anything from 23,976 / 24 / 25) and speed downs.
And the program actually offers several encoding format options and it preserves the 5.1 channels nicely.
When you use the option “without pitch correction” it will adapt the audio to the new length while correcting the pitch to sound right; if you choose “with pitch correction”, the program will adapt the audio to the new length and the audio will remain as it was with the source.
You can adapt to some NTSC sources or PAL by simply pretending 23,976 is 29,970 - sometimes it works, depending on the scene changes (I have tried with Star Trek DS9 and Voyager, on some episodes it worked, on others it didn’t). If you still have to cut the audio to fit, I recommend “Shotcut”: It allows you to cut and alter the audio while keeping the channels intact, it also offers lossless output, so you can later use meGui to change it back into a smaller AC3 that has a similar size to what you had before.
I really suggest you look into it, those are (so far) the only two free software solutions that preserve channels up to 5.1 configuration, which is nice.