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I'm trying to use ffmpeg to convert a h264/aac video file to an xvid/mp3 file so I can play it in my ultra-cheap media player.

At the moment the converted video file is TWICE the size of the original mp4. Is there any way to get a smaller file size without loosing too much quality? Even a drop to -qmin 1 is pretty awful!

The command i'm using is

ffmpeg -i input.mp4 -vcodec libxvid -sameq -acodec libmp3lame -ab 128k -ac 2 output.avi

And the ffmpeg output is

  Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'input.mp4'
  Metadata:
    major_brand     : isom
    minor_version   : 1
    compatible_brands: isomavc1
  Duration: 01:34:27.69, start: 0.000000, bitrate: 1520 kb/s
    Stream #0.0(und): Video: h264, yuv420p, 720x304 [PAR 1:1 DAR 45:19], 1387 kb/s, 25 fps, 25 tbr, 25k tbn, 50 tbc
    Stream #0.1(und): Audio: aac, 48000 Hz, stereo, s16, 128 kb/s
Output #0, avi, to 'output.avi':
  Metadata:
    ISFT            : Lavf52.64.2
    Stream #0.0(und): Video: mpeg4, yuv420p, 720x304 [PAR 1:1 DAR 45:19], q=2-31, 200 kb/s, 25 tbn, 25 tbc
    Stream #0.1(und): Audio: libmp3lame, 48000 Hz, stereo, s16, 128 kb/s
Stream mapping:
  Stream #0.0 -> #0.0
  Stream #0.1 -> #0.1
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5  
xvid isn't as good at compression as h264. What did you expect? –  phogg Dec 30 '10 at 17:23
    
try using the two pass parameter –  hbdgaf Dec 30 '10 at 17:27

2 Answers 2

Depending on what your media player can handle, you can reduce the frame size, e.g. if it starts as 1280x720, decrease to 640x360. That would let you reduce the video bitrate by 3/4 without changing the quality, and smaller video players only display 640 pixels wide anyway.

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As has been said before in comments, h.264 is a better (as in compresses better) codec than xvid, so with all other things being equal (quality, framesize, framerate etc.) xvid will always produce larger files. the upside to xvid is that it's less CPU intensive than h.264 which is why cheap media players can use it.

Case in point, XBMC on the original xbox (which had a CPU of PIII architecture running at 733 MHz) could be coerced into playing 720p HD content, but only if the codec was lightweight enough and with very specific flags. this was typically xvid as h.264 even in SD resolutions was usually too much for the poor old PIII. at SD resolutions a typical acceptable Q 45 min tv show weighs in around 350 Mb, but in h.264 would be around half that.

for your best bet, re-code the videos to the same res as the device (but keeping the quality), that way you're not wasting any bandwidth on image that's only going to be downscaled at playback time anyway. - halving the resolution in any direction (say 1280x720 -> 640x360 as mentioned above) will reduce the required bandwidth (and resulting filesize) to 1/4.

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