[vdr] Re: Idea: Change DVB card while recording

[Klaus Schmidinger <Klaus.Schmidinger@cadsoft.de>]

Uwe Freese wrote:
> 
> Hello Klaus,
> 
> >> > A perfect solution for me would be that VDR "starts" recording on the
> >> > second card on the same channel, makes a binary comparison of the
> >> > received streams and then stops the recording on the first card without
> >> > loss of any audio/video-data after the correct synchronization.
> 
> KS> Although this might be technically possible, I don't believe it's
> KS> worth the effort because it would introduce pretty complex mechanisms
> KS> in the otherwise clear and straightforward structures of VDR.
> 
> You mean, the frequent analyzing of if it's time to switch to another
> card? I can imagine that this could be complex.
> 
> KS> Implementing a method to "free" the primary interface upon user request
> KS> appears to me to be the better solution.
> 
> KS> I could imagine a solution where the user, when he wants to change the channel,
> KS> gets prompted something like "Continue recording on another DVB card?" (only
> 
> That would be ok for me and it would be less complex to implement this
> manual function, you're right.
> 
> Nevertheless, it would be nice if vdr can do this without data loss, i
> mean with this buffer analyzing I described.
> 
> I made two instant recordings (one minute RTL) and compared the files.
> It's like I imagined, in the middle, the files are nearly the same
> (looks like a few bytes differ every n bytes, it could be a time code or
> so in the video stream that the dvb cards create?).
> 
> Without looking at the vdr source code, I think that the actual
> thread/procedure/object that writes one stream to a file cannot handle
> two streams and merge them together.
> 
> I've two ideas of how to change this:
> 
> - One could implement an object before the "file-writer" that can handle
>   two streams (for the few seconds when recording overlapping) and that
>   only gives the stream to the "file-writer" that exists now unchanged,
>   when in "normal operating mode".
>   That would be some sort of big change in vdr.
> 
> - The recording on the new card can first start recording in a new file
>   and then the old recording thread stops. That should result in an
>   overlapping recording.
>   Then, a new "overlapping recording check" can test after a recording
>   has finished, if a vdr.00x exists with a greater number (that means
>   overlapping recording) and in this case, the redundant data at the
>   end of the own file is cut off.
>   I think this method could be implemented cleanly without destroying
>   the source code too much.

As I said: technically this is certainly possible - but I really don't think
it is worth building all this complex (and error prone) stuff into VDR, just
for a very rare case...

Klaus
-- 
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Klaus Schmidinger                       Phone: +49-8635-6989-10
CadSoft Computer GmbH                   Fax:   +49-8635-6989-40
Hofmark 2                               Email:   kls@cadsoft.de
D-84568 Pleiskirchen, Germany           URL:     www.cadsoft.de
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