[FFmpeg-user] reusing same passlog file.

[Dennis]

Trying to figure out way to minimize NFS reads of passlog and mbtree files
on a diskless server.

pass 1:
ffmpeg -i /nfs/source.m2v -pass 1 output.mp4
this creates: ffmpeg2pass-0.log.mbtree and ffmpeg2pass-0.log.

now to create two pass2 files, there has to be a `ln` or `copy` command to
create a separate log for each pass2 video output track:
ln ffmpeg2pass-0.log.mbtree ffmpeg2pass-1.log.mbtree
ln ffmpeg2pass-0.log ffmpeg2pass-1.log

pass2 (two outputs):
ffmpeg -i /nfs/source.m2v  -pass 2 -s 640x480 vga.mp4   -pass 2 -s 320x240
qvga.mp4

Can FFmpeg uses exactly same set of passlog files in both pass2's. Can it
read the same passlog and mbtree file and provide it  to multiple video
output processes, as long as "passlogfilename" is specified?

Otherwise once this scales up, it results in heavy traffic of mbtree files.