[MEncoder-users] many mencoder questions from a newbie

[belcampo]

On 12/19/2011 10:52 AM, Janos Szamosfalvi wrote:
> Howdy,
>
> I'm trying to use mencoder to create quality mp4's playable
> on a lowly Velocity Cruz T301 tablet, and I have a few questions
> about mencoder.
>
>
> First, I was looking for a download link on the mplayer site for the
> latest version of mencoder, but I couldn't find it.
> I have: "MEncoder Sherpya-SVN-r30521 (C) 2000-2010 MPlayer Team"
> Is there a newer version available somewhere?
>
>
> In a log like below:
> Pos:   2.7s     75f (55%)  8.81fps Trem:   0min   1mb  A-V:0.011 [1942:127]
> Pos:   2.7s     76f (55%)  8.75fps Trem:   0min   1mb  A-V:0.014 [1961:128]
> Pos:   2.8s     77f (55%)  8.72fps Trem:   0min   1mb  A-V:0.017 [1976:127]
> what does the A-V section, and the numbers in the [ ] bracket mean?
>
>
> What do these telecine numbers mean?
> telecine = 1.5  0.243
> telecine = 1.5  -0.054
> telecine = 1.0  -0.279
> the first one is always 1.0 or 1.5 as far as I can see,
> the 2nd seems to be between -0.5 and 0.5
>
>
> Is there some document that describes the content of the x264 info at
> the end of the encoding?
> x264 [info]: frame I:15    Avg QP:13.43  size: 25791  PSNR Mean Y:55.78 U:55.67 V:59.12 Avg:56.13 Global:49.73
> x264 [info]: frame P:220   Avg QP:17.15  size:  7385  PSNR Mean Y:50.96 U:51.06 V:55.24 Avg:51.41 Global:47.31
> [...]
> x264 [info]: ref B L1: 96.8%  3.2%
> x264 [info]: SSIM Mean Y:0.9926010
> x264 [info]: PSNR Mean Y:54.671 U:54.939 V:58.797 Avg:55.133 Global:47.369 kb/s:1521.26
> I think I can guess some of these fields, but most aren't exactly
> clear to me.
>
> Because the tablet I have appears to be a bit underpowered, it is
> crashing on sections that (I presume) are encoded with higher
> bitrate, so I figured that I will use "vbv_maxrate" to set an
> upper limit about 10% above the average bitrate, but as far
> as I can see, it has no effect.  With a bitrate of 1500,
> I tried maxrate of 1800, 1700, 1600, 1500, 1400, 1200 but
> the resulting .mp4 files turned out to be identical....
> Any idea on why is that happening?   At least for the last 2,
> it should've just erred out.
>
> Here are my commandlines for a 2 pass encoding:
>
> mencoder Title4.mpg -ss 4 -of lavf -lavfopts format=mp4 -o /dev/null -ofps 30000/1001 -vf crop=720:464:0:8,scale=720:432,harddup -ovc x264 -x264encopts turbo:pass=1:bitrate=1500:subq=4:frameref=2:8x8dct:bframes=3:b_pyramid=normal:weight_b:keyint=30:vbv_maxrate=1600:threads=auto:psnr:ssim -srate 44100 -af format=s16le -oac mp3lame -lameopts cbr:br=128
>
> mencoder Title4.mpg -ss 4 -of lavf -lavfopts format=mp4 -o Title4h.mp4 -ofps 30000/1001 -vf crop=720:464:0:8,scale=720:432,harddup -ovc x264 -x264encopts pass=2:bitrate=1500:subq=5:frameref=3:8x8dct:bframes=3:b_pyramid=normal:weight_b:keyint=30:vbv_maxrate=1600:threads=auto:psnr:ssim -srate 44100 -af format=s16le -oac mp3lame -lameopts cbr:br=128
Partly answer, first you may check if your tablet is able to play 
HighProfile files. The HighProfile 8x8dct:bframes=3 might give you troubles.
Further you might try crf=20 instead of bitrate=1500:vbv_maxrate=1600
crf takes the amount of bits it needs for "quality 20". Your quality 
comes at QP:13.43 and QP:17.15 for I and P frames, this is somewhat 
high. Where lower numbers mean higher quality. Maybe it's something to 
start with.
>
> TIA
>
>
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