Hi, I want to scientifically measure some experiments, therefore I first need duration (timecode) calibration.
However, I observe inconsistencies, may be due to my wrong use of ffmpeg, can you help. Test process: 1/ I recorded a chronometer lapse of about 25s on my smartphone with a camera. 2/ Then I want to use ffmpeg to slow down the recorded video by a factor 10 and burn the associated timecode (cli at end of msg). 3/ I visually compare the burnt timecode with the one recorded. I notice, that the time discrepency between the burnt timecode and the recorded one varies according to start, middle and end of the video. To better show it, attached pictures extracted with: ffmpeg -ss 240 -t 0.05 -i timeCslow.mp4 -q:v 1 ss240_img%d.png and ffmpeg -ss 60 -t 0.05 -i timeCslow.mp4 -q:v 1 ss60_img%d.png Oddly, the difference between the last 2 snapshots are 30sec!! What's wrong? Thanks. P.S. Link to video and output https://drive.google.com/file/d/0B752iWgZhOl6Q0VBNU1zT2hPeFU/view?usp=sharing https://drive.google.com/file/d/0B752iWgZhOl6Mk1lNm4wT3M0OEE/view?usp=sharing https://drive.google.com/file/d/0B752iWgZhOl6eDZBYnZ1SE9BTzQ/view?usp=sharing https://drive.google.com/file/d/0B752iWgZhOl6Y1RFUzZtY1IwMkE/view?usp=sharing https://drive.google.com/file/d/0B752iWgZhOl6QzgxTXYtWFY5NzA/view?usp=sharing REF: http://ffmpeg.org/ffmpeg-filters.html#setpts_002c-asetpts ffmpeg -ss 3.9 -i timeC2.mp4 -c:v libx264 -vf "crop=in_w-16*20:in_h-7*20:8*20:4*20,setpts=10*PTS, drawtext=fontfile='C\:\\Windows\\Fonts\\arial.ttf':timecode='00\:00\:00\:00':r=29.97:x=(w-tw)/2:y=h-(2*lh):fontsize=128:fontcolor=red:box=1:[email protected]" -preset ultrafast -crf 30 -an timeCslow.mp4 F:\>ffmpeg -ss 3.9 -i timeC2.mp4 -c:v libx264 -vf "crop=in_w-16*20:in_h-7*20:8*20:4*20,setpts=10*PTS, drawtext=fontfile='C\:\\Windows\\Fonts\\arial.ttf':timecode='00\:00\:00\:00':r=29.97:x=(w-tw)/2:y=h-(2*lh):fontsize=128:fontcolor=red:box=1:boxcolor=blue @0.5" -preset ultrafast -crf 30 -an timeCslow.mp4 ffmpeg version N-68694-g7c210c4 Copyright (c) 2000-2014 the FFmpeg developers built on Dec 25 2014 22:13:21 with gcc 4.9.2 (GCC) configuration: --enable-gpl --enable-version3 --disable-w32threads --enable-avisynth --enable-bzlib --enable-fontconfig --enable-frei0r --enable-gnutls --enable-iconv --enable-libass --enable-libbluray --enable-libbs2b --enable-libcaca --enable-libfreety pe --enable-libgme --enable-libgsm --enable-libilbc --enable-libmodplug --enable-libmp3lame --enable-libopencore-amrnb --enable-libopencore-amrwb --enable-libopenjpeg --enable-libopus --enable-librtmp --enable-libschroedinger --enable-libsoxr --enable-libs peex --enable-libtheora --enable-libtwolame --enable-libvidstab --enable-libvo-aacenc --enable-libvo-amrwbenc --enable-libvorbis --enable-libvpx --enable-libwavpack --enable-libwebp --enable-libx264 --enable-libx265 --enable-libxavs --enable-libxvid --enab le-decklink --enable-zlib libavutil 54. 15.100 / 54. 15.100 libavcodec 56. 16.100 / 56. 16.100 libavformat 56. 16.102 / 56. 16.102 libavdevice 56. 3.100 / 56. 3.100 libavfilter 5. 5.101 / 5. 5.101 libswscale 3. 1.101 / 3. 1.101 libswresample 1. 1.100 / 1. 1.100 libpostproc 53. 3.100 / 53. 3.100 Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'timeC2.mp4': Metadata: major_brand : MSNV minor_version : 19595353 compatible_brands: MSNVmp42isom creation_time : 2014-11-26 13:44:44 Duration: 00:00:29.03, start: 0.000000, bitrate: 8866 kb/s Stream #0:0(und): Video: mpeg4 (Advanced Coding Profile) (mp4v / 0x7634706D), yuv420p, 1280x720 [SAR 1:1 DAR 16:9], 8799 kb/s, 29.97 fps, 29.97 tbr, 30k tbn, 30k tbc (default) Metadata: creation_time : 2014-11-26 13:44:44 handler_name : Video Media Handler Stream #0:1(und): Audio: aac (LC) (mp4a / 0x6134706D), 24000 Hz, mono, fltp, 64 kb/s (default) Metadata: creation_time : 2014-11-26 13:44:44 handler_name : Sound Media Handler [libx264 @ 000000000581f200] using SAR=1/1 [libx264 @ 000000000581f200] using cpu capabilities: MMX2 SSE2Fast SSSE3 SSE4.2 AVX [libx264 @ 000000000581f200] profile Constrained Baseline, level 3.1 [libx264 @ 000000000581f200] 264 - core 144 r2525 40bb568 - H.264/MPEG-4 AVC codec - Copyleft 2003-2014 - http://www.videolan.org/x264.html - options: cabac=0 ref=1 deblock=0:0:0 analyse=0:0 me=dia subme=0 psy=1 psy_rd=1.00:0.00 mixed_ref=0 me_range=16 chr oma_me=1 trellis=0 8x8dct=0 cqm=0 deadzone=21,11 fast_pskip=1 chroma_qp_offset=0 threads=6 lookahead_threads=1 sliced_threads=0 nr=0 decimate=1 interlaced=0 bluray_compat=0 constrained_intra=0 bframes=0 weightp=0 keyint=250 keyint_min=25 scenecut=0 intra_r efresh=0 rc=crf mbtree=0 crf=30.0 qcomp=0.60 qpmin=0 qpmax=69 qpstep=4 ip_ratio=1.40 aq=0 Output #0, mp4, to 'timeCslow.mp4': Metadata: major_brand : MSNV minor_version : 19595353 compatible_brands: MSNVmp42isom encoder : Lavf56.16.102 Stream #0:0(und): Video: h264 (libx264) ([33][0][0][0] / 0x0021), yuv420p, 960x580 [SAR 1:1 DAR 48:29], q=-1--1, 29.97 fps, 30k tbn, 29.97 tbc (default) Metadata: creation_time : 2014-11-26 13:44:44 handler_name : Video Media Handler encoder : Lavc56.16.100 libx264 Stream mapping: Stream #0:0 -> #0:0 (mpeg4 (native) -> h264 (libx264)) Press [q] to stop, [?] for help frame= 7522 fps=519 q=-1.0 Lsize= 33682kB time=00:04:10.98 bitrate=1099.4kbits/s dup=6769 drop=0 video:33651kB audio:0kB subtitle:0kB other streams:0kB global headers:0kB muxing overhead: 0.091521% [libx264 @ 000000000581f200] frame I:31 Avg QP:20.16 size: 67376 [libx264 @ 000000000581f200] frame P:7491 Avg QP:23.00 size: 4321 [libx264 @ 000000000581f200] mb I I16..4: 100.0% 0.0% 0.0% [libx264 @ 000000000581f200] mb P I16..4: 2.3% 0.0% 0.0% P16..4: 30.5% 0.0% 0.0% 0.0% 0.0% skip:67.2% [libx264 @ 000000000581f200] coded y,uvDC,uvAC intra: 26.5% 56.8% 22.4% inter: 10.1% 12.1% 2.2% [libx264 @ 000000000581f200] i16 v,h,dc,p: 19% 53% 18% 10% [libx264 @ 000000000581f200] i8c dc,h,v,p: 35% 41% 18% 6% [libx264 @ 000000000581f200] kb/s:1098.34 F:\> _______________________________________________ ffmpeg-user mailing list [email protected] http://ffmpeg.org/mailman/listinfo/ffmpeg-user
