[mythtv-users] grabbing individual frames/images for "poster"

Michael T. Dean mtdean at thirdcontact.com
Tue Nov 1 10:45:33 EST 2005

Bill Evans wrote:

> I'm trying to implement a simple image grabber, either as a (user) 
> filter or perhaps differently.  I'd like to be able to:
> (1) specify a specific time (or frame) in a .nuv file and grab that 
> frame as a jpeg; I know I don't know enough about the frame process to 
> know the best way to do it, but I'd like it to be as complete a frame 
> as possible (without pixelation, incomplete blocks, etc).
> The current method of using mplayer and the "-vo jpeg:..." works in 
> that it'll create a lot of jpeg images for me.  However, I really 
> don't want to create that many images and don't want to go through 
> them all.  When I specify an offset into the show (with "-sb x" or 
> "-ss x") and limit it with "-frames 10", it starts giving me partial 
> blocks.  I have to use 10 for frames since it does not tend to give me 
> an image if I specify only 1 frame.
> I'm doing this wrong.  Even if I'm close to doing it correctly with 
> this tool, it doesn't seem to be the most efficient.  When asking 
> mplayer to go "deep" into a show, it appears to take a while 
> processing everything ahead of it.  I'm sure that this is possible at 
> least on a small level, but is there a better way?
> (2) Anyway, once this works consistently and accurately, I'd like to 
> automate it into a script so that I can call it as a user filter.  I'd 
> like to be able to look in the mysql database and find either the 
> bookmark's location or use editing marks to determine which frame(s) 
> to grab as images.  (Where to store them is secondary at this point 
> and, I suspect, easy to safely configure.)
> I don't really care at this point if the images are useful to current 
> mythtv programs; though that is perhaps my #3 goal, the first two 
> would be a 90% solution for my needs.

This is very similar to what Risto Treksler's patch for the MythTV 
preview images does.  It creates a PNG thumbnail image by taking into 
account the user-specified offset, the commercial cutlist, and--if set 
to generate a preview pixmap from the bookmark location--the bookmark 


So, what problem are you attempting to fix here?  Are you just trying to 
create a way to force creation of thumbnails or planning to use the 
JPEG's for DVD menu creation or ... ?


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