x264: output video-file shorter then input.

[oLex]

i've encoded a video (xvid avi-file, 512x384, btrt ~ 2000 kbps, 25 fps) using MeGUI (x264 rev.616, 618, 620):

--pass 2 --bitrate 500 --stats ".stats" --keyint 350 --ref 16 --mixed-refs --no-fast-pskip --bframes 3 --b-pyramid --b-rdo --bime --weightb --direct auto --filter 1,1 --subme 7 --trellis 2 --analyse all --8x8dct --vbv-maxrate 768 --me umh --thread-input --progress --no-psnr --no-ssim --output "x:\v.264" "x:\v.avs"

script:

DirectShowSource("x:\v.avi",fps=25,audio=false)

length of source: 20.33:400,
length of target: 20.33:480, but it has excess 2-second part of movie at the end. as result "true" length of target is about 20.31.

what's wrong? any ideas?

[bond]

- how many frames does virtualdub report for the .avs script?
- are there b-frames used in the .avi? which codec?
- what happens if you use avisource()?
- what happens if you encode without using b-frames?
- what happens if you encode with b-frames but without b-pyramid?

[oLex]

log of 1st pass:

avis [info]: 512x384 @ 25.00 fps (30837 frames)
x264 [info]: using cpu capabilities MMX MMXEXT SSE SSE2 3DNow!
x264 [info]: slice I:242 Avg QP:28.52 size: 18003
x264 [info]: slice P:13913 Avg QP:30.63 size: 4337
x264 [info]: slice B:16682 Avg QP:32.39 size: 729
Index Type(1) chunks(30834)
Index Type(2) chunks(30824)
Index Type(1) chunks(30834)
Index Type(2) chunks(30824)
x264 [info]: mb I I16..4: 48.1% 0.0% 51.9%
x264 [info]: mb P I16..4: 15.2% 0.0% 0.0% P16..4: 42.6% 0.0% 0.0% 0.0% 0.0% skip:42.2%
x264 [info]: mb B I16..4: 0.5% 0.0% 0.0% B16..8: 8.5% 0.0% 0.0% direct:10.8% skip:80.1%
x264 [info]: final ratefactor: 28.84
x264 [info]: direct mvs spatial:98.6% temporal:1.4%
x264 [info]: kb/s:498.5

encoded 30837 frames, 50.16 fps, 498.60 kb/s

log of 2nd pass:

avis [info]: 512x384 @ 25.00 fps (30837 frames)
x264 [info]: using cpu capabilities MMX MMXEXT SSE SSE2 3DNow!
mp4 [info]: initial delay 2 (scale 25)
x264 [info]: slice I:242 Avg QP:27.56 size: 20774
x264 [info]: slice P:13913 Avg QP:30.07 size: 4185
x264 [info]: slice B:16682 Avg QP:31.72 size: 831
Index Type(1) chunks(30834)
Index Type(2) chunks(30824)
Index Type(1) chunks(30834)
Index Type(2) chunks(30824)
x264 [info]: mb I I16..4: 15.3% 75.2% 9.5%
x264 [info]: mb P I16..4: 3.3% 3.0% 1.1% P16..4: 51.3% 9.0% 5.7% 0.2% 0.0% skip:26.3%
x264 [info]: mb B I16..4: 0.1% 0.2% 0.0% B16..8: 30.0% 0.4% 0.8% direct: 1.0% skip:67.4%
x264 [info]: 8x8 transform intra:46.8% inter:69.4%
x264 [info]: direct mvs spatial:92.5% temporal:7.5%
x264 [info]: ref P 51.5% 16.4% 10.1% 3.9% 3.1% 3.3% 2.8% 1.2% 1.1% 1.1% 1.0% 1.1% 0.9% 0.9% 0.9% 0.5%
x264 [info]: ref B 67.3% 13.8% 5.8% 2.6% 1.9% 1.9% 1.6% 0.8% 0.7% 0.7% 0.6% 0.6% 0.6% 0.6% 0.5%
x264 [info]: kb/s:500.2

encoded 30837 frames, 3.79 fps, 500.22 kb/s

desired video bitrate of this job: 500 kbit/s - obtained video bitrate (approximate): 502 kbit/s

there are 2 max consecutive b-frames used in the source. codec is xvid 1.2-127 (koepi's build)

- what happens if you use avisource()?
- what happens if you encode without using b-frames?
- what happens if you encode with b-frames but without b-pyramid?

i will try tomorrow...

[akupenguin]

DirectShowSource has been known to randomly drop frames and then make up stuff at the end to fill the nominal duration of the movie.

[oLex]

all variations with b-frames finished by same results. only avisource() finished by minimal difference of lengths.
thanx!