[GEM-dev] filmFFMPEG: img_convert -> sws_scale?

[Jim McCann]

Hello,
	I was compiling Gem against a recent ffmpeg and noticed that it  
still uses the img_convert call, along with, perhaps, some other  
deprecated functionality. I patched it [img_convert] out thusly:

(filmFFMPEG.cpp @ 314)
	// was: if (img_convert(&rgba,dstfmt,&m_Picture,fmt,width,height)<0)
	//Patched to use swsscale instead of img_convert:
	static SwsContext *sws_context = NULL;
	sws_context = sws_getCachedContext(sws_context, width, height, fmt,  
width, height, dstfmt, 0, NULL, NULL, NULL);
	if (!sws_context)
	  error("ffmpeg-conversion failed (%d->%d)", fmt, dstfmt);
	else if (sws_scale(sws_context, m_Picture.data, m_Picture.linesize,  
0, height, rgba.data, rgba.linesize)<0)
	  error("ffmpeg-conversion failed (%d->%d)", fmt, dstfmt);

(also added swscale.h to the header; added -lswscale with  
PKG_CONFIG_FFMPEG)

However,
	(a) I'm not sure this is a great option, since sws_getCachedContext  
will de- and re- allocate contexts repeatedly, e.g. if decoding  
multiple streams of different sizes. If there is there a way to make  
that SwsContext per-object, it would work better.
	(b) haven't found a test video that actually works yet (I have  
mostly .mkv's and ffmpeg gives a decode error on 'em).
	(c) From all the #defines in the code, it seems like multiple- 
version compatibility is really important, and -- of course -- this  
also breaks that.
	(d) there is other deprecated stuff yet to patch out, but see (c).

Anyway, figured I'd email this list and see if anyone was working on  
it or had suggestions.

Good day,

--Jim