Re: [Vnc2swf-users] Shrinking a vnc2flv file
Status: Alpha
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From: Brian C. <B.C...@po...> - 2009-11-06 16:20:59
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On Fri, Nov 06, 2009 at 03:40:29PM +0000, Brian Candler wrote: > The encoder looks like it should skip unchanged blocks in the same way as > vnc2swf. I'm just building it from source now. If it still makes flv files > larger than it's probably just a simple bug to squash. I've found the issue, and it's simply due to the frequency of insertion of key frames. By default, ffmpeg is putting a key frame in every second, whereas vnc2flv does it much less frequently - something like one every 150 frames. You can change ffmpeg's behaviour using -g (for "group of pictures"). Taking my 19MB vnc2flv file, and using ffmpeg built from SVN: ffmpeg -i src.flv -vcodec flashsv -acodec copy -r 12 -g 120 same.flv gives a file which is 13.5MB. And scaling it down by 2:1 at the same time, ffmpeg -i src.flv -vcodec flashsv -acodec copy -s 496x304 -r 12 -g 120 half.flv gives a file which is 11.7MB. Remember this includes audio too. I am still a bit surprised that the resizing doesn't reduce the output much, but I am still doing 12 fps here, so 4 fps would probably reduce it more. I haven't yet worked out how the block_height and block_width are set, and whether it's possible to override these too. Regards, Brian. |