I needed to split a video into different segments and fit them all on one DVD but ended up slighly over the size limit to do so. One of the .mp4 segments 55 minutes long that I saved as a direct stream copy with virtualdub came out at 485 megabytes. So I used virtualdub and reset the mp4 target bitrate in that segment to a bitrate of 650 instead of what was given in the box when I opened it at 700.
Then I put it through a fast recompress and the file size was significantly smaller at 342 megabytes instead of 485 megabytes. I played this smaller size video and it played fine, sound and video were synched throughout the movie, beginning and endings were there, the time of the movie was given the same at 55 minutes, and everything seemed fine. Can anyone comment on this. I do these things on a trial and error basis but I don't really understand why things happen the way they do. Why did the slight reduction in bitrate cause such a large 143 megabyte deduction in file size. Will what I did have any bad effects on the video? I haven't noticed any.
+ Reply to Thread
Results 1 to 4 of 4
In Direct Stream Copy mode all VirtualDub does is copy the compressed video from the input file to the output file. It can't change the bitrate or the codec. The difference between 700 Mb/s and 650 Mb/s wouldn't cause your file to shrink from 485 MB to 342 MB. It should have gone down to about 450 MB at the smallest (if no audio). Look elsewhere for the "missing" data. How are you checking the bitrates? Some programs don't accurately report bitrates. Try using Bitrate Viewer.
How much bitrate any particular video needs depends on the nature of the video, the codec and settings used.
WHY ARE YOU TALKING SO LOUDLY?
Ok, much of the shortcuts you are using are fruitless, because you are ultimately going to DVD, and that means you will have to reencode to MPEG2.
Remember, FILESIZE = BITRATE & RUNNING TIME.
maybe he's burning as a data disc, not dvd-video ?
how are you exporting mp4 out of vdub ? external encoder feature? x264vfw commandline ? or did you really mean AVI ?
Also, if you are doing a 1pass ABR, it's not uncommon to miss the target bitrate, expecially if you are using something like xvid - jagabo mentioned bitrate viewer - that's a good idea to verify the actual bitrate. When you calculate bitrate you need to add in audio bitrate as well