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Chewi
Developer
Joined: 01 Sep 2003
Posts: 886
Location: Edinburgh, Scotland
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 Posted: Thu Oct 05, 2006 5:28 pm Post subject: [SOLVED] ffmpeg -vcodec mpeg4 -> bad quality? |
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Hi guys. Any video encoding experts around? I've got a puzzle for you. I'm getting really bad output from lavc's mpeg4 codec when using ffmpeg. However if I use the same codec with all the equivalent options in mencoder, the result is crystal. The result is also crystal if I use ffmpeg with xvid instead of lavc. I'm using the 20060530 snapshot from Portage.
| Code: | ffmpeg -i test.avi -pass 1 -acodec mp3 -ar 44100 -ab 128 -vcodec mpeg4 -b 1024 -bt 1 -qmin 2 -qmax 20 -lelim -4 -celim 9 -lumi_mask 0.05 -dark_mask 0.01 -bf 2 -r 25 -mbd 1 -me_range 1023 -s 640x480 -f avi /dev/null
ffmpeg -i test.avi -pass 2 -acodec mp3 -ar 44100 -ab 128 -vcodec mpeg4 -b 1024 -bt 1 -qmin 2 -qmax 20 -lelim -4 -celim 9 -lumi_mask 0.05 -dark_mask 0.01 -bf 2 -r 25 -mbd 1 -me_range 1023 -s 640x480 -f avi output.avi |
Bad! (ffmpeg with mpeg4)
| Code: | ffmpeg -i test.avi -pass 1 -acodec mp3 -ar 44100 -ab 128 -vcodec xvid -b 1024 -bt 1 -qmin 2 -qmax 20 -lelim -4 -celim 9 -lumi_mask 0.05 -dark_mask 0.01 -bf 2 -r 25 -mbd 1 -me_range 1023 -s 640x480 -f avi /dev/null
ffmpeg -i test.avi -pass 2 -acodec mp3 -ar 44100 -ab 128 -vcodec xvid -b 1024 -bt 1 -qmin 2 -qmax 20 -lelim -4 -celim 9 -lumi_mask 0.05 -dark_mask 0.01 -bf 2 -r 25 -mbd 1 -me_range 1023 -s 640x480 -f avi output.avi |
Good! (same options but with xvid)
| Code: | mencoder test.avi -o /dev/null -oac mp3lame -lameopts cbr:br=128 -ovc lavc -lavcopts vcodec=mpeg4:vbitrate=1024:vhq:vpass=1:vqmin=2:vqmax=20:vlelim=-4:vcelim=9:lumi_mask=0.05:dark_mask=0.01:vmax_b_frames=2 -af resample=44100 -vf scale=640:480 -ofps 25
mencoder test.avi -o output.avi -oac mp3lame -lameopts cbr:br=128 -ovc lavc -lavcopts vcodec=mpeg4:vbitrate=1024:vhq:vpass=2:vqmin=2:vqmax=20:vlelim=-4:vcelim=9:lumi_mask=0.05:dark_mask=0.01:vmax_b_frames=2 -af resample=44100 -vf scale=640:480 -ofps 25 |
Good! (equivalent options in mencoder with mpeg4)
Here's the test video. http://www.aura-online.co.uk/~chewi/test.avi Look out for artifacts trailing behind the globe and notice how the stars go very blurry. They should remain quite sharp. I know I've used a lot of options but I had very similar results even with much fewer options. I think I must be missing some important option. And I know reencoding this seems a little pointless but it's just a test for something much more exciting. Any help would be much appreciated. 
Last edited by Chewi on Fri Oct 06, 2006 9:47 am; edited 1 time in total |
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Gusar
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Joined: 09 Apr 2005
Posts: 2665
Location: Slovenia
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| Posted: Thu Oct 05, 2006 5:50 pm Post subject: |
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Xvid and lavc-mpeg4 don't really take the same options, so some of the things you specified don't actually have an effect with xvid.
As for the difference between ffmpeg and mencoder - I'm not sure, but it's possible that they have different defaults, so all options you haven't specified may have different values in mencoder than they do in ffmpeg. |
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Chewi
Developer
Joined: 01 Sep 2003
Posts: 886
Location: Edinburgh, Scotland
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| Posted: Thu Oct 05, 2006 6:14 pm Post subject: |
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| Yeah I guessed both of those might be the case. I don't think any of the options should be making it that bad though and I did try with fewer. I think it must be down to some option I'm missing. |
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Chewi
Developer
Joined: 01 Sep 2003
Posts: 886
Location: Edinburgh, Scotland
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| Posted: Fri Oct 06, 2006 9:46 am Post subject: |
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| Aha. Figured it out. I misunderstood the meaning of bit tolerance (-bt), which is the only option I hadn't set in mencoder. Setting it higher is a good thing. |
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