target file size when encoding video
I was just wondering how to set a target file size when encoding media (on the command line).
I prefer ffmpeg over mencoder and I am trying to rip DVD VOB files to H.264 inside mp4 containers (libx264). All of the examples I found say to use mencoder with a negative bitrate e.g. -700000 for a 700mb output file. However, I have tried copying several of these example command lines (even ones dealing with divx etc) verbatim and I never get the target file size. With a 1.2gb VOB file, I get roughly 250mb output using mencoder if I use -700000 or -175000. A few people have told me to use Windows tools or to play it and at the same time, capture the screen output. I don't want to do either of these. So, again, how can this be done on the command line (preferably with ffmpeg but I will settle for anything). If any maths is involved to calculate bitrates or whatever then I have no problem with that either. As I understand it, it requires 2 pass VBR but I have had no luck even trying to give it calculated bitrates. |
I know there's the '-fs' option for ffmpeg but it might just always truncate. I wanted to try it with 2 pass encoding, maybe it has a different effect ?
Anyway for constant bitrate you can calculate the output size like it says here: http://www.mplayerhq.hu/DOCS/HTML/en...vd-mpeg4-2pass Quote:
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