[MEncoder-users] Hidden Intros in Videos

[Matt Shaw]

Hey list,

I've come across a weird problem - at least weird to me, since I don't deal
with video that often.

I'm trying to encode a batch of DV NTSC videos to H.264. When I watch the
source video in Quicktime, I see 30 seconds of video. This is good. After I
encode the video, I watch the mp4 and it is now 40 seconds long and it has a
10 second intro at the beginning. The intro is along the lines of "Bob's
Test Promo #1234". It's not a generic promo that's somehow finding it's way
into the encode. Each intro is specific to each video.

1) How does Quicktime know to ignore the first N seconds? It just completely
pretends it's not there. This info must be in the video file headers or
something.

2) Is there a name for this? I've had a hard time Googling "Hidden video
intro"

I'm aware that I can trim the video beginning of the video with -ss
00:00:10. The problem is that I have a ton of videos and the length of the
intro varies (some don't have intros). So I'm looking for a way to
automatically detect this intro (as Quicktime is able to) and trim
accordingly.

Thanks
Matt