Hello!

I've tried reading through a number of threads on here about adding subtitles hard into the video stream with mencoder, but most of them are people asking how to do it or having problems. So apologies if this has already been asked somewhere, but I haven't found it yet.

I don't have any problem getting mencoder to add the subtitles. But I only actually want to add a subtitle (for credits) during the first say 20 seconds of the video, and it seems a shame to have to re-encode all the rest just for that.

So I was wondering about different ways to split off the first n seconds of video to render subtitles onto, then join it back on the remainder untouched. Obviously, I would need to use the same parameters to re-encode the bit with the subtitles, but if I try to split the file on a key frame or something like that, would this work OK when I join them back together? Is there any easy way to find the right byte offset of an avi (xvid stream) to split it right on a key frame? Or maybe it doesn't quite work the way I think it does at all?

I don't have a great deal of experience messing with video really, so all advice welcomed...thanks!

will get you the first 20 seconds of the video to a file. Use the rest of the parameters that you want to.

will get you the rest of the movie untouched to a file.

Then join them together

Great, thank you!

It seems obvious now that you spelled it out
Didn't occur to me that mencoder could just join them with -ovc copy, I was thinking I would need to cat the two parts back together so I was overcomplicating the whole thing.

Cheers!

I finally got a chance to test this out today, but I found a slight problem. It seems that -ss will only seek to the next key frame, not the exact position, so in my example file, the first 20 seconds were extracted correctly, but rest_of_movie.avi actually began about 4 seconds later than it should have.

So, is there any way to either:

1) Identify the first key frame located after 20 seconds (for making first_20_sec.avi to the right point)?

-or-

2) Seek exactly to 00:00:20 position (presumably by replaying from the previous key frame instead)?

Perhaps the first way would be best so that the key frames remain evenly spaced? But I can't find any options in mencoder/mplayer to locate the byte offset (as could be used in -endpos) for a suitable key frame point at which to split the file.

Can anybody help me here?