[Ffmpeg-devel] ffmpeg MP4/H264 Help Please

[Andrei Verovski aka MacGuru]

Hi !

I have posted this question to ffmpeg-user list, but there seem to be very few 
people. So I have decided to listen the truth from the originators of this 
amazing piece of software. Sorry to bother you, guys, but the ffmpeg in-depth 
information resources are really scarce.


Anyone can suggest me what is the best option to convert QuickTime MOVs, DVD 
VOBs, and 1200-1900 kbps MP4 (too high rate for so small motion), containing 
low-motion video with a lot of color images, so colors must be preserved to 
reasonably highest-quality variable-rate MP4/H264, compatible with QuickTime 
Player?

Since this is basically a screen capture, files can be really very small (but 
as I said before, preserving right colors is absolutely important, because 
this is capture of onscreen Photoshop work).

Digging in ffmpeg docs and net I found 2 possible solutions:

1) -----------------------

ffmpeg -y -i "$1" -v 1 -vcodec h264 -crf 21 -refs 5
-loop 1 -deblockalpha 0 -deblockbeta 0 -parti4x4 1 -partp8x8 1 -partb8x8 1 
-me umh -subq 6 -brdo 1 -me_range 21 -chroma 1 -slice 2 -bf 1
-bframebias 1 -b_strategy 1 -g 250 -keyint_min 25 -sc_threshold 40
-rc_eq 'blurCplx^(1-qComp)' -qcomp 0.60 -qmin 7 -qmax 35
-acodec aac -ab 64 -ar 48000 -ac 2 "$1.ffmpeg.mp4"

There were additional options, but I had to remove them after ffmpeg upgrade.

# ffmpeg-0.4.9-7.pm.svn20060918 - removed options:
# -max_qdiff 4 -i_quant_factor 0.71428572 -b_quant_factor 
0.76923078 -rc_max_rate 0 -rc_buffer_size 0

Result: QuickTime MOVs compressed 3-7 times, VOBs around 2.5 - 3 times, 
quality is very good, although images went darker. Sometimes produces files 
with too high data rate (1700 kbps).


2) --- VisualHub video converter for Mac, high-quality setting

ffmpeg -y ?-i $1 -s -vcodec h264 ?-g 300 ?-qmin 23 ?- 
b 2304.0 ?-bf 1 ?-loop 1 -sc_threshold 40 -partp4x4 1 -rc_eq ?
'blurCplx^(1-qComp)' -refs 3 ? -async 50 ?-acodec aac ?-ar 48000 -ac ?
2 -ab 64"$1.ffmpeg.mp4"

Result: files much smaller than script #1, especially VOBs (4.7 GB DVD went to 
only 450 MB), but data rate for some titles is suspiciosly small (150 kbps at 
720x480 resoslution).


So, the questions are:

1) Which script is better to produce variable rate MP4/H264? Is "-crf 21" more 
or less equal to "-qmin 23" in terms of qualaity? Visally it very hard to tell 
the difference.

2) Is it necessary to deinterlace VOBs?

3) How to resample existing constant-rate MP4/H264 to variable-rate MP4/H264 
without visual loss/degradation of color information? Can ffmpeg understand, 
that it do not have to change format and convert video, just discard unwanted 
frames.

Thanks in advance for any suggestion.