Days of Bike and Photos

Measured performance of ffmpeg’s x264 quality presets, to know which option is the best for my purpose converting mpeg2 ts to Apple TV mp4. Factors need to be considered are 1) conversion speed, 2) file size and 3) quality of the video. The most important factor is conversion speed, which would be nice if the time for conversion is shorter than for recording. For file size off course, the smaller the better as the space of my Apple TV storage is limited.

Test Method

The test was done with ffmpeg version 0.6.1 on 2.8GHz Intel Core i7 running Mac OS X 10.6.8 as;

for i in ultrafast superfast veryfast faster fast medium slow slower veryslow placebo
do ffmpeg -i sample.ts -threads 4 -vcodec libx264
      -vpre $i -vpre main -crf 18 -s 1280x720
      -acodec libfaac -ab 160k
      -y $i.mp4
done

sample.ts is a 60 seconds of full HD (1440×1080) mpeg2 video.
Test Results



	

		
preset used for conversion
Conversion speed (fps - frames per second) 
Size of the output video file (in bytes)
	


	

		
ultrafast
29.6
81,046,858
	
	

		
superfast
27.9
58,180,478
	
	

		
veryfast
20.6
43,968,615
	
	

		
faster
13.0
32,981,783
	
	

		
fast
9.1
35,461,071
	
	

		
medium
8.0
35,119,322
	
	

		
slow
5.6
33,367,247
	
	

		
slower
2.1
33,698,347
	
	

		
veryslow
1.3
29,697,663
	
	

		
placebo
0.6
29,395,288
	




On my environment, ultrafast can convert ts video almost at the recording speed (29.97 fps). But my decision was to go with superfast as its fps is closer to ultrafast yet the size is much smaller.
		

子供と。

入店待ち45分の昼食のデザート。

「速過ぎる」と怒られたので帰路は子供のペースで。

Followings are the points;

• -newaudio to add another track
• -alang to specify audio language

tssplitter_lite input.ts /dev/stdout 304 | \
  ffmpeg -i - -ss 1 -threads 2 \
    -vcodec libx264 -vpre fast -vpre main -crf 18 \
    -s 720x480 -r 30000/1001 -aspect 4:3 -vsync 1 -level 31 \
    -acodec libfaac -ab 130k -async 10 -ac 2 -alang jpn \
    -map 0.0 -map 0.1 -map 0.2 \
    -y ~/tmp/output.mp4 \
    -acodec libfaac -ab 130k -async 10 -ac 2 -alang eng -newaudio