[FFmpeg-user] Why start_time is sometimes non zero?

[Christian Johannesen]

I know files captured with Final Cut Pro 7 have this attribute. The
software starts recording the audio and video tracks and then inserts
metadata for each track to indicate the offset of the start of the track
relative to the start time of the container. This aligns the tracks, to
this point.

Chris

On Friday, March 20, 2015, Andrzej Borucki <borucki.andrzej at gmail.com>
wrote:

> I convert .mov file created by Canon to H.264, container mp4 - QuickTime(?)
> ffprobe give me:
> [format]
> format_name=mov,mp4,m4a,3gp,3g2,mj2
> format_long_name=QuickTime / MOV
> start_time=0.045000
> duration=7.808000
> size=954931
>
> video stream [streams.stream.0]
> codec_name=h264
> codec_time_base=1/180000
> time_base=1/90000
> start_pts=5940
> start_time=0.066000
> duration_ts=702702
> duration=7.807800
> bit_rate=810598
> nb_frames=234
>
> audio [streams.stream.1]
> codec_name=aac
> codec_time_base=1/48000
> time_base=1/48000
> start_pts=2160
> start_time=0.045000
> duration_ts=372736
> duration=7.765333
>
> After converting it to h264:
> [format]
> start_time=-0.033333
> duration=7.842000
> size=889221
> bit_rate=907136
>
> [streams.stream.0]
> r_frame_rate=30000/1001
> avg_frame_rate=30000/1001
> time_base=1/30000
> start_pts=0
> start_time=0.000000
> duration_ts=235235
> duration=7.841167
>
> [streams.stream.1]
> time_base=1/48000
> start_pts=-1600
> start_time=-0.033333
> duration_ts=374336
> duration=7.798667
>
> Why start_time is not zero? In second movie, audio begins before or after
> start movie?
> In first  - both video and audio start_time is non zero, what it means?
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