• Compression Techniques

  Wrong aspect ratio when AVCHD converted to MP4

  Posted by Johan Wadman on November 30, 2010 at 8:01 pm

  Hi!
  I have a video recorder from Sony producing AVCHD content and storing to memory card.
  It is stated to record at a 1080i.
  ffmpeg says that the original .mts-file is 1440×1080 with DAR 16:9 and PAR 4:3.
  ffmpeg –i 00001.MTS
Input #0, mpegts, from '00001.MTS':
Duration: 00:02:42.24, start: 1.000033, bitrate: 11531 kb/s
Program 1
Stream #0.0[0x1011]: Video: h264, yuv420p, 1440x1080 [PAR 4:3 DAR 16:9], 50 fps, 50 tbr, 90k tbn, 50 tbc
Stream #0.1[0x1100]: Audio: ac3, 48000 Hz, stereo, s16, 256 kb/s
Stream #0.2[0x1200]: Subtitle: pgssub

  The .MTS-container and the AC3-audio is not supported on my Samsung TV.
  Therefore I am converting it with ffmpeg to MP4 container and mp3 audio.
  I do this with
  ffmpeg -i 00001.MTS -vcodec copy -acodec libmp3lame output.mp4
...
Input #0, mpegts, from '00001.MTS':
Duration: 00:02:42.24, start: 1.000033, bitrate: 11531 kb/s
Program 1
Stream #0.0[0x1011]: Video: h264, yuv420p, 1440x1080 [PAR 4:3 DAR 16:9], 50 fps, 50 tbr, 90k tbn, 50 tbc
Stream #0.1[0x1100]: Audio: ac3, 48000 Hz, stereo, s16, 256 kb/s
Stream #0.2[0x1200]: Subtitle: pgssub
File 'output.mp4' already exists. Overwrite ? [y/N] y
Output #0, mp4, to 'output.mp4':
Metadata:
encoder : Lavf52.64.2
Stream #0.0: Video: libx264, yuv420p, 1440x1080 [PAR 4:3 DAR 16:9], q=2-31, 50 tbn, 25 tbc
Stream #0.1: Audio: libmp3lame, 48000 Hz, stereo, s16, 64 kb/s
...

  The only problem is that when played on the Samsung TV it is shown as 4:3 content. (People look taller and black areas on left-end and right-end sides.)
  My guess is that Samsung TV don’t care about the PAR 4:3 and uses PAR 1:1 instead.
  Then since 1440/1080 equals 4/3 this is what I get.
  So I believe I need to convert 1440×1080 DAR 16:9,PAR4:3 to 1920×1080 DAR 16:9, PAR 1:1 ?
  The question is then how do I do that with ffmpeg???
  Best regards Johan

  Marcin Ok replied 13 years, 5 months ago 3 Members · 3 Replies
• 3 Replies

• 

  Michael Rampe

  December 1, 2010 at 1:42 am

  [johan wadman] “My guess is that Samsung TV don’t care about the PAR 4:3 and uses PAR 1:1 instead. So I believe I need to convert 1440×1080 DAR 16:9,PAR4:3 to 1920×1080 DAR 16:9, PAR 1:1 ?
  The question is then how do I do that with ffmpeg???”

  I agree. since the Samsung device is not respecting the container aspect flag, you will need to re-compress the stream instead of using -vcodec copy.

  As you have quite a high bitrate original, you will need to specify that.

  one pass example:
  ffmpeg -i 00001.MTS -vcodec libx264 -vpre medium -b 11000k -s 1920×1080 -aspect 16:9 -acodec libmp3lame -ab 256k output.mp4

  two pass example:
  ffmpeg -i 00001.MTS -vcodec libx264 -vpre medium_firstpass -b 11000k -bt 11000k -s 1920×1080 -aspect 16:9 -an -pass 1 /dev/null && ffmpeg -i 00001.MTS -vcodec libx264 -vpre medium -b 11000k -bt 11000k -s 1920×1080 -aspect 16:9 -acodec libmp3lame -ab 256k -pass 2 output.mp4

  Depending on the content, you should be able to get acceptable quality at a lower bitrate so do some experiments.

  Michael
• 

  Johan Wadman

  December 1, 2010 at 9:20 pm

  Hi!
  I just tested and now it is correctly displayed!
  Thanks Michael!
  /Johan
• 

  Marcin Ok

  March 2, 2013 at 11:38 am

  This is very helpful. Do you maybe also know how the command would look like to also convert 50p to 50i?

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