[MPlayer-users] Re: Tools for mpeg* to DVD
Corey Hickey
bugfood-ml at fatooh.org
Fri Dec 19 07:04:52 CET 2003
rcooley wrote:
>>B frames require big motion estimate search radii and are
>>unfriendly to predictive motion estimators
>
>
> I think it's pretty much universal opinion of the more knowledgable
> users on this mailing list, that B-frames are useless. I personally
> haven't yet seen a case where B-frames improve quality and/or reduce
> filesizes.
>
>
I don't know about mpeg-2, but with mpeg-4 a single b-frame usually
increases PSNR slightly (while more than one is almost always bad).
The table below is for a one-minute clip I usually test on, that I
selected to be an even mix between fast and slow motion scenes.
+------------------+-------+-------+
| params | psnr | fps |
+------------------+-------+-------+
| :vmax_b_frames=1 | 41.48 | 63.11 |
| : | 41.34 | 74.68 |
| :vmax_b_frames=2 | 41.26 | 59.68 |
| :vmax_b_frames=3 | 41.01 | 57.79 |
| :vmax_b_frames=4 | 40.71 | 56.97 |
| :vmax_b_frames=5 | 40.42 | 56.83 |
+------------------+-------+-------+
As for the price/performance ratio, see the table below for a comparison
to trell, mbd=2, and mbd=1.
psnr_% = the psnr for each test divided by the psnr of ":"
fps_% = the fps for each test divided by the fps of ":"
asdf = the psnr increase for each test with respect to ":",
divided by the fps decrease with respect to ":"
(so, this is "psnr gain for each fps lost")
+------------------+-------+-------+--------+-------+-----------+
| params | psnr | fps | psnr_% | fps_% | asdf |
+------------------+-------+-------+--------+-------+-----------+
| :trell | 41.63 | 58.98 | 100.70 | 0.79 | 0.001015 |
| :mbd=2 | 41.54 | 56.94 | 100.48 | 0.76 | 0.000821 |
| :vmax_b_frames=1 | 41.48 | 63.11 | 100.34 | 0.85 | 0.000334 |
| :mbd=1 | 41.43 | 62.29 | 100.22 | 0.83 | 0.000234 |
| : | 41.34 | 74.68 | 100.00 | 1.00 | -0.000000 |
| :vmax_b_frames=2 | 41.26 | 59.68 | 99.81 | 0.80 | -0.000264 |
| :vmax_b_frames=3 | 41.01 | 57.79 | 99.20 | 0.77 | -0.001270 |
| :vmax_b_frames=4 | 40.71 | 56.97 | 98.48 | 0.76 | -0.002582 |
| :vmax_b_frames=5 | 40.42 | 56.83 | 97.77 | 0.76 | -0.003809 |
+------------------+-------+-------+--------+-------+-----------+
While the performance isn't exactly stellar compared to "the big two",
trell and mbd=2, it does edge out mbd=1 (note that that's 334 vs 234, if
your eyes are trying to trick you like mine just did to me).
Don't kill me if I messed up the math. :)
-Corey
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