Frame rate problem with ffmpeg

[AngryBonk]

I´m trying to reencode a 3vid file to an SVCD. My problem is the source file having a frame rate of 29.75 (don´t ask me why anyone would like to encode it that way). So it´s no surprise that encoding with NTSC framerate results in sync problems.

Is there any workaround? Does the "unspecified" framerate option help here and if yes would my dvd play it without probs in 29.75?

Thanks!

[galactica]

I´m trying to reencode a 3vid file to an SVCD. My problem is the source file having a frame rate of 29.75 (don´t ask me why anyone would like to encode it that way). So it´s no surprise that encoding with NTSC framerate results in sync problems.

Is there any workaround? Does the "unspecified" framerate option help here and if yes would my dvd play it without probs in 29.75?

Thanks!

correct me if im wrong, but isnt
NTSC (NTSC Film)
Video:
max 2600 kbit/sec MPEG-2 (Audio + Video bitrate max bitrate is 2778 kbit/s).
480 x 480 pixels (CVD 352x480)
29,97 frames/second


wouldnt you want to encode it to SVCD using the SAME frame rate as NTSC FILM (with out 3:2 pulldown) to get it synced?

just my 2cents

[AngryBonk]

No, you´re not wrong. You just misunderstood me. I indeed wanted to encode with a 29.97 framerate to get a standard compliant SVCD.

My problem is, that the _source_ I have has a framerate of 29.75, not the 29.97 I would need.

As the only options with ffmpeg are NTSC, NTSC film and PAL nothing suits resulting in sync problems.

What about the 3:2 option? I had "set 3:2" checked. I see now that I should not have done that. But does unchecking solve my problem? There´s no info on the ffmpegx website regarding these buttons.

[galactica]

sorry, you've stumped me.
Only thing i can say is to get your hands on an older version of ffmpegx where the frame rates were stated by number and not by name.
see if it has the frame rate you want.

Or try another mpeg encoding app
I vaguely remember one where you can type in the frame rate you want it to use, but am blanking on its name and even if it exists!

[Mr Mxyzptlk]

I'll give you the reader's digest version of a tutorial that I plan to post here in the future. However it is not for the faint of heart & takes much longer than most conventional methods. The bonus though, is that out of almost two dozen or more other methods I've tried, this produces the highest quality end result I've seen using ffmpegX. It completely removes quicktime out of the process and is an all-in-one ffmpegX process.

First you must run your source file through the "fast DivX" preset, making sure that the frame rate is exactly that of the original (in your case 29.75). Any re-sizing that might be needed should also be done during this step. If your video and audio are separate files, you should take this opportunity to use the "Add audio..." section under the "Audio" tab. You may also choose to use the "High Quality", "4 motion vectors" and "Two-pass encoding" settings under the "Options" tab to retain as much of the source as possible.

Next, take the resulting file and run it through the "DivX (libavc)" preset, using your desired frame rate (This time, in your case 29.97). Any cropping that might be needed should be done during this step. This is a great opportunity to use any of the filters that mencoder has to offer, such as "Brightness/Contrast", "Denoise", "Dering" and "Deblock". Again, You may also choose to use the "High Quality", "4 motion vectors", "Two/Three-pass encoding", "Trellis quantization" and "Quarter pixel ME (qpel)" settings under the "Options" tab to retain as much of the source as possible.

After many hours later (18 hrs for a 90 min source on my G4 400) you are now ready to send the resulting file Through the DVD preset you feel is best suited for your needs. Just be sure that you use the same frame rate you chose in the last step (29.97). Keep in mind that by going through these steps, you now have the benefit of using the "Decode with mplayer" option under the "Options" tab without fear that your result will not sync up properly. Although decoding with mplayer is a tad slower, the difference in quality is unbelievable.

For anyone who chooses to use this method:
Please do not get upset if something unforeseen happens during the process. I realize this might invest a lot of time only to see negative results. However you have to realize that from time to time $#it happens and the best way to deal with it is to calmly backtrace your steps and find a solution. That being said, I use this method all the time & it has never failed me. In fact most of the time, after filters are applied, I end up with a better output than the source file.

Anywho,
Hee Haw and Merry Christmas

[AngryBonk]

Thanks guys!

I´ll see if that works.

[Guest99]

Mxyzptlk, could you describe why you are apparently re-encoding a video file THREE times???

This cannot be a good thing!

Unless you apply some sort of losless compression for the intermediate steps, the quality will degrade with each step.


A quick description of -why- you are doing each step would be helpful, also, why this method is also applicable to "correct" 29.97 sources.



Thanks.