[MEncoder-users] Usage of -ofps

[Björn Nadrowski]

That works!
Thanks a lot!
Ciao, Bjoern

Giacomo Comes wrote :
> On Sun, Oct 21, 2007 at 06:51:46PM +0200, Bj?rn Nadrowski wrote:
> > Hello, 
> > I would like to ask a question concerning the use of -ofps
> > 
> > Let's suppose I want to prepare a movie for my nokia e90's
> > internal realplayer.
> > In order to do this, I use the following commands:
> > 
> > V_BITRATE=800
> > X_SCALE=640
> > Y_SCALE=352
> > V_NAME=film.avi
> > BASENAME=`echo ${V_NAME} | cut --delimiter='.' --fields=1`
> > 
> > mencoder -ofps $FPS -o temppi.m4v -of rawvideo \
> > 		    -oac copy -ovc lavc -lavcopts vcodec=mpeg4:vbitrate=${V_BITRATE}:threads=2 \
> > 		    -vf lavcdeint,scale=${X_SCALE}:${Y_SCALE} -lavdopts threads=2 \
> 
>   		    -vf lavcdeint,scale=${X_SCALE}:${Y_SCALE},harddup -lavdopts threads=2 \
> 
> should fix the problem
> 
> Giacomo
> 
> > 		    ${V_NAME}
> > 
> > mplayer -vo null -vc null -ao pcm:fast ${V_NAME}
> > faac --mpeg-vers 4 audiodump.wav
> > 
> > MP4Box -new -add temppi.m4v -add audiodump.aac -fps $FPS \
> >    -brand mp42 -isma ${BASENAME}${1}-${V_BITRATE}-${FPS}-${X_SCALE}.mp4
> > 
> > Audio is always fine and faac results into an audio track which has a duration of
> > 2597.2 seconds, which is only 0.1 seconds longer than the film
> > (deduced using mplayer -v:)
> > ==> Found video stream: 0
> > ====== STREAM Header =====
> > Type: vids   FCC: xvid (64697678)
> > Flags: 0
> > Priority: 0   Language: 0
> > InitialFrames: 0
> > Rate: 24000/1001 = 23.976
> > Start: 0   Len: 62269
> > Suggested BufferSize: 90898
> > Quality 10000
> > Sample size: 0
> > ==========================
> > and 
> > 62269/23.976=2597.13880547214
> > 
> > 
> > 
> > Now, above commands seem ok for values of FPS < 23;
> > for this range of values, the length of the video matches closely the length 
> > of the audio track. 
> > However, when approaching FPS=24, the video becomes shorter and shorter,
> > leading to very substantial audio/video desync, for extreme values, the video 
> > even plays back in a visibly accelerated speed. 
> > 
> > Is this the expected behavior?
> > I have no idea where this comes from , and would like to know the commands which 
> > allow me to specify the FPS value I want (well, it would be sufficient to
> > know the commands which allow encoding without audio/video desyncing; but not using
> > ofps and FPS at all does not resolve the problems, in this case, the video is 10 minutes
> > shorter than the original one...)
> > 
> > I attach a list of FPS - Duration values, 
> > which I obtained for a series of encodings using different values of FPS and
> > I extracted the duration of the movie using
> > MP4Box -info film.mp4
> > 
> > I also attach a figure which displays this curious behavior. 
> > 
> > THanks for any help, Bjoern
> > 
> > #FPS   Duration
> > 10.0	2597.2
> > 10.5	2597.14
> > 11.0	2597.18
> > 11.5	2597.22
> > 12.0	2597.17
> > 12.5	2597.2
> > 13.0	2597.15
> > 13.5	2597.18
> > 14.0	2597.14
> > 14.5	2597.17
> > 15.0	2597.13
> > 15.5	2597.1
> > 16.0	2597.06
> > 16.5	2596.97
> > 17.0	2596.82
> > 17.5	2596.8
> > 18.0	2596.5
> > 18.5	2596.43
> > 19.0	2596.26
> > 19.5	2596.26
> > 20.0	2596.1
> > 20.5	2595.85
> > 21.0	2595.71
> > 21.5	2595.63
> > 22.0	2595.59
> > 22.5	2595.33
> > 23.0	2595.48
> > 23.5	2595.23
> > 24.0	2592.08
> > 24.5	2539.18
> > 25.0	2488.4
> > 25.5	2439.61
> > 26.0	2392.69
> > 26.5	2347.55
> > 27.0	2304.07
> > 27.5	2262.18
> > 28.0	2221.78
> > 28.5	2182.81
> > 29.0	2145.17
> > 29.5	2108.81
> > 30.0	2073.67
> > 30.5	2039.67
> > 31.0	2006.77
> > 31.5	1974.92
> > 32.0	1944.06
> > 32.5	1914.15
> > 33.0	1885.15
> > 33.5	1857.01
> > 34.0	1829.7
> > 34.5	1803.19
> > 35.0	1777.43
> > 35.5	1752.39
> > 36.0	1728.06
> > 36.5	1704.38
> > 37.0	1681.35
> > 37.5	1658.93
> > 38.0	1637.11
> > 38.5	1615.84
> > 39.0	1595.13
> > 39.5	1574.94
> > 
> 
> 
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> > MEncoder-users at mplayerhq.hu
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> 
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