ugoiras: increase quality of webm samples.

Fix certain ugoiras having very low quality webm samples. This was
because we had a target bitrate of 5 Mbps, but this wasn't enough for
videos that were high resolution or that had choppy, hard-to-compress
motion, such as post 5081776 (nsfw).

app/logical/media_file/ugoira.rb

@@ -85,7 +85,7 @@ class MediaFile::Ugoira < MediaFile
       end
 
       ext = zipfile.first.name.match(/\.(\w{,4})$/)[1]
-      ffmpeg_out, status = Open3.capture2e("ffmpeg -i #{tmpdir}/images/%06d.#{ext} -codec:v libvpx -crf 4 -b:v 5000k -an #{tmpdir}/tmp.webm")
+      ffmpeg_out, status = Open3.capture2e("ffmpeg -i #{tmpdir}/images/%06d.#{ext} -codec:v libvpx -crf 12 -b:v 0 -an #{tmpdir}/tmp.webm")
       raise Error, "ffmpeg failed: #{ffmpeg_out}" unless status.success?
 
       mkvmerge_out, status = Open3.capture2e("mkvmerge -o #{output_file.path} --webm --timecodes 0:#{tmpdir}/timecodes.tc #{tmpdir}/tmp.webm")