[FFmpeg-user] cannot seek into png 'video'

Thorsten von Eicken tve at voneicken.com
Tue Oct 1 17:44:49 EEST 2019

On 10/1/19 12:35 AM, Moritz Barsnick wrote:
> Moin Thorsten,
> On Tue, Oct 01, 2019 at 00:56:33 +0000, Thorsten von Eicken wrote:
>> I'm trying to put an overlay over a video and I'm having difficulties
>> seeking into the png in order to time-shift the video and overlay
>> relative to one another.
> I don't really understand what you are trying to do, neither from this
> sentence:
>> If I'd now like to skip the first 10 seconds of the overlay in order to
>> line up the timing better I try to use:
> "Line up timing" or "time shift" are nice terms, but all "-ss" does it
> to shift the starting point of the input file to a certain point. E.g.
> "-ss 10" skips the first 10 seconds.

The png input is not a single static image, it is a sequence of images, 
i.e. a video in png format. Like mjpeg but png. There is one image per 
second as the overlay is not static, it's showing GPS info (speed, track 
position, etc). The problem I have is that it's not trivial to 
synchronize the overlay with the video. I generate the overlay from a 
GPS track recording and the video comes from an action cam. So after 
generating the overlay I'd like to tweak the synchronization by skipping 
a few frames at the start of either of the video or of the overlay. Does 
that make sense?



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