[mythtv] [PATCH] position map using frame numbers, rev 2

[Edward Wildgoose]

Would I be really naive to try applying this and testing against DVB?

Thanks

-----Original Message-----
From: Doug Larrick [mailto:doug at ties.org]
Sent: 11 December 2003 12:59
To: mythtv-dev at mythtv.org
Subject: [mythtv] [PATCH] position map using frame numbers, rev 2


OK, 0.13 is out... here's my revised patch for using frame numbers as  
the positionmap index in avformatdecoder.

In contrast to the last version, this patch retrieves positionmap from  
variously the db, the current encoder, or from parsing the stream,  
depending on what mode we're in (live tv, watching recording, watching  
prerecorded).

I've tested this pretty well with HDTV streams.  It has seen no testing  
with other sources.

It also works OK on recordings with no positionmap at all, though  
performance isn't great fast-forwarding by large chunks since it has to  
seek through the skipped frames one by one.  With no positionmap, it  
re-computes the bitrate based on how much data has actually been seen  
so as to get a more accurate picture of the actual length of the  
recording.  There may be a better way to do this, but I don't know what  
it is.

I have removed my old, more complex keyframe distance measuring code,  
because for the streams where this made a difference, we no longer  
depend on keyframe distance at all.

Note that, in order to switch Mythtv entirely away from using a  
positionmap keyed by keyframe number, I would have had to make similar  
nontrivial changes to ivtvdecoder as I did to avformatdecoder.  Since I  
do not have one of these cards (and so couldn't test it), I am  
unwilling to make these changes.

I have also fixed a couple bugs in hdtvrecorder where it was misparsing  
the stream, missing some GOP start and picture start headers.

-Doug




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