Dear list members,
I am analysing a video from a security cam which has recorded a traffic
accident. I want to calculate the speeds of the vehicles involved and
therefore need the exact time gap between each two frames.
When analysing the video with ffprobe it turns out that the time gap is
not constant, which is what I suspected from the space gaps between the
vehicle positions in the frames.
I however wonder where 'best_effort_timestamp_time' stems from. "best
effort" suggests that the timestamp cannot really be trusted (?).
In this very case, I will be able to test the video timing at the spot
(using a turntable or alike as a target), but rather often, the cameras
are already dismounted when I come into play, thus this is a question
that matters when settling litigation issues ...
BTW: What are those frames that are neither I- nor P-frames?
Wolfgang Hugemann
Screen dump:
ffprobe -show_frames -show_entries
frame=best_effort_timestamp_time,key_frame,pict_type input.avi
ffprobe version N-88042-g72c3d9ae45 Copyright (c) 2007-2017 the FFmpeg
developers
built with gcc 7.2.0 (GCC)
configuration: --enable-gpl --enable-version3 --enable-sdl2
--enable-bzlib --enable-fontconfig --enable-gnutls --enable-iconv
--enable-libass --enable-libbluray --enable-libfreetype
--enable-libmp3lame --enable-libopenjpeg --enable-libopus
--enable-libshine --enable-libsnappy --enable-libsoxr --enable-libtheora
--enable-libtwolame --enable-libvpx --enable-libwavpack --enable-libwebp
--enable-libx264 --enable-libx265 --enable-libxml2 --enable-libzimg
--enable-lzma --enable-zlib --enable-gmp --enable-libvidstab
--enable-libvorbis --enable-cuda --enable-cuvid --enable-d3d11va
--enable-nvenc --enable-dxva2 --enable-avisynth --enable-libmfx
libavutil 56. 0.100 / 56. 0.100
libavcodec 58. 0.100 / 58. 0.100
libavformat 58. 0.100 / 58. 0.100
libavdevice 58. 0.100 / 58. 0.100
libavfilter 7. 0.100 / 7. 0.100
libswscale 5. 0.100 / 5. 0.100
libswresample 3. 0.100 / 3. 0.100
libpostproc 55. 0.100 / 55. 0.100
Input #0, avi, from 'C:\Temp\Motorradvideo\20150424_200000_0301_crop.avi':
Metadata:
encoder : Lavf55.0.100
Duration: 00:00:05.00, start: 0.000000, bitrate: 418 kb/s
Stream #0:0: Video: h264 (Constrained Baseline) (H264 /
0x34363248), yuv420p(progressive), 704x576, 277 kb/s, 6 fps, 6 tbr, 6
tbn, 12 tbc
Stream #0:1: Audio: pcm_s16le ([1][0][0][0] / 0x0001), 8000 Hz, 1
channels, s16, 128 kb/s
[FRAME]
key_frame=1
best_effort_timestamp_time=0.000000
pict_type=I
[/FRAME]
[FRAME]
key_frame=1
best_effort_timestamp_time=0.000000
[/FRAME]
[FRAME]
key_frame=1
best_effort_timestamp_time=0.060125
[/FRAME]
[FRAME]
key_frame=1
best_effort_timestamp_time=0.120250
[/FRAME]
[FRAME]
key_frame=0
best_effort_timestamp_time=0.166667
pict_type=P
[/FRAME]
[FRAME]
key_frame=1
best_effort_timestamp_time=0.180375
[/FRAME]
[FRAME]
key_frame=1
best_effort_timestamp_time=0.240500
[/FRAME]
[FRAME]
key_frame=1
best_effort_timestamp_time=0.300625
[/FRAME]
[FRAME]
...
_______________________________________________
ffmpeg-user mailing list
[email protected]
http://ffmpeg.org/mailman/listinfo/ffmpeg-user
To unsubscribe, visit link above, or email
[email protected] with subject "unsubscribe".
