[FFmpeg-user] corruption when performing scripted extraction using -ss and -t

[np.mdbr]

Hi All,

I've scripted the extraction of clips from a large MP4 file.  However, each
clip that is extracted displays corrupted video/grey screen for
approximately the first five seconds, then it displays the expected output.

The main MP4 file was acquired using VLC's command line interface.  I had to
use VLC because the capture card currently available uses 'crossbars',
something that ffmpeg cannot handle at this time.  I've listed the two
commands below.

First command (in VLC, to acquire main video file):
vlc -I rc dshow:// --sout
"#transcode{vcodec=h264,sfilter=marq{marquee=%Y-%m-%d%H:%M:%S,refresh=500,x=10,y=10,position=5},fps=29.97,vb=300}:std{mux=ts,access=file,dst=c:\vlc.mp4}"

Second command (using ffmpeg, to extract specific time periods from the main
video file; timings are in seconds, floating point values):
ffmpeg -ss <clipStart> -t <duration> -i <input_file> -b:v <bitrate of parent
file> -filter:v <calculated pixel area> <new file name>

Thanks for your help.



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