[FFmpeg-user] Somewhat confused by these results

[Philip Rhoades]

People,

I had a commercial firm turn old, professional, Beta recordings into 
digital files (two out of the eight tapes were not recoverable - anyone 
know of any gurus in that area?) and I was supplied with uncompressed 
Quicktime MOVs that had four audio and one video track.

After using:

   mencoder ./Midway_NuclearFree.mov -mf fps=25 -o Midway_NuclearFree.avi 
-ovc lavc -oac mp3lame -lavcopts vcodec=mpeg4

which produced a very small AVI but it was very bitty (the test tape I 
used was of scenes with lots of movement on Sydney Harbour - choppy 
waves and boat movements etc) so I started looking at ffmpeg.  In a 
script I have this line (ie only testing the first six minutes of the 
original file):

   ffmpeg -t 6:00 -i Midway_NuclearFree.mov -c:v libx264 -preset $speed 
-qp 0 Midway_NuclearFree_${i}_${speed}.mkv

or this:

   ffmpeg -t 6:00 -i Midway_NuclearFree.mov -c:v libx264 -preset $speed 
Midway_NuclearFree_${i}_${speed}.mkv

gave these results (in MB):

67	Midway_NuclearFree_0_placebo.mkv
66	Midway_NuclearFree_1_veryslow.mkv
74	Midway_NuclearFree_2_slower.mkv
75	Midway_NuclearFree_3_slow.mkv
79	Midway_NuclearFree_4_medium.mkv
80	Midway_NuclearFree_5_fast.mkv
73	Midway_NuclearFree_6_faster.mkv
65	Midway_NuclearFree_7_veryfast.mkv
94	Midway_NuclearFree_8_superfast.mkv
200	Midway_NuclearFree_9_ultrafast.mkv

2442	Midway_NuclearFree_0_placebo_qp0.mkv
2442	Midway_NuclearFree_1_veryslow_qp0.mkv
2445	Midway_NuclearFree_2_slower_qp0.mkv
2451	Midway_NuclearFree_3_slow_qp0.mkv
2460	Midway_NuclearFree_4_medium_qp0.mkv
2467	Midway_NuclearFree_5_fast_qp0.mkv
2500	Midway_NuclearFree_6_faster_qp0.mkv
2518	Midway_NuclearFree_7_veryfast_qp0.mkv
2519	Midway_NuclearFree_8_superfast_qp0.mkv
2949	Midway_NuclearFree_9_ultrafast_qp0.mkv

 From these results it appears to me that:

- selecting the speed has very little effect on file size (except for 
Midway_NuclearFree_9_ultrafast.mkv)

- selecting qp = 0 has a dramatic effect on file size - compared to 
leaving it out - but again, the speed option had very little additional 
effect on file size

- ALL of these outputs eyeball fine to me compared to the original 
Mencoder avi!

Any comments?

Thanks,

Phil.
-- 
Philip Rhoades

PO Box 896
Cowra  NSW  2794
Australia
E-mail:  phil at pricom.com.au