[FFmpeg-user] ffmpeg -ss start-time issue

[richard heade]

I'm a newbie, I've just started using ffmpeg, so I fully expect that I'm
doing something wrong and I could use some help.  I'm using "ffmpeg
input.mpg -ss 123.456 -t 12.345" to extract a clip from an mpeg 2 file. 
It works really well except for one significant problem, ffmpeg and I
(or avidemux) don't agree on where 123.456 is.  I use avidemux to
determine the start time, 123.456.  Avidemux2_gtk allows me to play the
video and at any point it displays the frame number, elapsed time and
frame type.

I'm running ffmpeg 2.1.1 with gcc 4.7.  It reports the video properties as:
 Duration: 03:04:56.08, start: 1.874000, bitrate: 10112 kb/s
    Stream #0:0[0x1e0]: Video: mpeg2video (Main), yuv420p(tv), 1280x720
[SAR 1:1 DAR 16:9], max. 24000 kb/s, 59.94 fps, 59.94 tbr, 90k tbn,
119.88 tbc
    Stream #0:1[0x80]: Audio: ac3, 48000 Hz, 5.1(side), fltp, 384 kb/s

I'm running Avidemux 2.5.6.  It reports the video properties as:
Video:
Codec 4CC: MPEG
Image Size: 1280x720
Aspect Ratio: 1:1
Frame Rate: 59.940 fps
Frame Count: 624061 frames
Total Duration: 02:53:31.428
Audio:
Codec: AC3
Channels: 6
Bitrate: 48000 Bps  / 384 kbps
Variable Bitrate: No
Frequency: 48000 Hz
Total Duration: 03:04:55.520
File Size: 507.91MB

It would unfortunate if avidemux and ffmpeg are just incompatible,
though I would accept that, because I haven't found another way to
accurately determine the starting position of a clip within a video.  If
they are incompatible is there another way, compatible with ffmpeg, to
get the frame count, elapsed time, and frame type from a video?