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• Detect rotation angle and rotate final video using ffmpeg version 2.8

  9 novembre 2017, par Hemant Kumar

  I used to work on ffmpeg 2.2 until now and was detecting rotation angle of video uploaded from android / iPhone mobiles and rotate the resulting video so that it run perfectly on a correct angle.

  But since I have updated the ffmpeg to version 2.8 I am getting this rotation problem. My queries are not rotating the videos as they were earlier.

  Here’r the commands I was using :

  To check rotation angle :

  ffprobe -of json -show_streams {$input} | grep rotate

  below is my final command to convert a video to mp4

  "ffmpeg -i {$input} -strict -2 -vcodec libx264 -preset slow -vb 500k -maxrate 500k -bufsize 1000k -vf 'scale=-1:480 ".fix_video_orientation($input)."' -threads 0 -ab 64k -s {$resolution}  -movflags faststart -metadata:s:v:0 rotate=0 {$output}";

  "fix_video_orientation" function is given below. It detect the angle of rotation of the initial video and output optimal option for rotating the final video.

  function fix_video_orientation($input){
  
  
  
  $return= ", transpose=1 ";
  
  
  
  $dd= exec("ffprobe -of json -show_streams  {$input}   | grep rotate");
  
  
  
  if(!empty($dd)){
  
  
  
  $dd=explode(":",$dd);
  
  $rotate=str_replace(",","",str_replace('"',"",$dd[1]));
  
  
  
  if($rotate=="90")return $return;
  
  
  
  else if ($rotate=="180") return ", transpose=2,transpose=2 ";
  
  
  
  else if($rotate == "270") return ", transpose=2 ";
  
  }

  Currently above script is supporting "flv","avi","mp4","mkv","mpg","wmv","asf","webm","mov","3gp","3gpp" extensions, also the script is supporting the resulting .mp4 file to play on all browsers and devices.

  Now the ffprobe command is not returning rotation angle and so a portrait video if uploaded from iphone is showing as landscape on the website.

  Output console of ffprobe command :

  ffprobe version N-77455-g4707497 Copyright (c) 2007-2015 the FFmpeg developers
  
  built with gcc 4.8 (Ubuntu 4.8.4-2ubuntu1~14.04)
  
  configuration: --extra-libs=-ldl --prefix=/opt/ffmpeg --mandir=/usr/share/man --enable-avresample --disable-debug --enable-nonfree --enable-gpl --enable-version3 --enable-libopencore-amrnb --enable-libopencore-amrwb --disable-decoder=amrnb --disable-decoder=amrwb --enable-libpulse --enable-libdcadec --enable-libfreetype --enable-libx264 --enable-libx265 --enable-libfdk-aac --enable-libvorbis --enable-libmp3lame --enable-libopus --enable-libvpx --enable-libspeex --enable-libass --enable-avisynth --enable-libsoxr --enable-libxvid --enable-libvo-aacenc --enable-libvidstab
  
  libavutil 55. 11.100 / 55. 11.100
  
  libavcodec 57. 20.100 / 57. 20.100
  
  libavformat 57. 20.100 / 57. 20.100
  
  libavdevice 57. 0.100 / 57. 0.100
  
  libavfilter 6. 21.101 / 6. 21.101
  
  libavresample 3. 0. 0 / 3. 0. 0
  
  libswscale 4. 0.100 / 4. 0.100
  
  libswresample 2. 0.101 / 2. 0.101
  
  libpostproc 54. 0.100 / 54. 0.100
  
  Input #0, mov,mp4,m4a,3gp,3g2,mj2, from '/standard/PORTRAIT.m4v':
  
  Metadata:
  
  major_brand : qt
  
  
  
  minor_version : 0
  
  compatible_brands: qt
  
  
  
  creation_time : 2016-02-03 05:25:18
  
  com.apple.quicktime.make: Apple
  
  com.apple.quicktime.model: iPhone 4S
  
  com.apple.quicktime.software: 9.2.1
  
  com.apple.quicktime.creationdate: 2016-02-03T10:52:11+0530
  
  Duration: 00:00:03.34, start: 0.000000, bitrate: 7910 kb/s
  
  Stream #0:0(und): Audio: aac (LC) (mp4a / 0x6134706D), 44100 Hz, mono, fltp, 63 kb/s (default)
  
  Metadata:
  
  creation_time : 2016-02-03 05:25:18
  
  handler_name : Core Media Data Handler
  
  Stream #0:1(und): Video: h264 (Main) (avc1 / 0x31637661), yuv420p(tv, bt709), 720x1280 [SAR 1:1 DAR 9:16], 7832 kb/s, 29.97 fps, 29.97 tbr, 600 tbn, 50 tbc (default)
  
  Metadata:
  
  creation_time : 2016-02-03 05:25:18
  
  handler_name : Core Media Data Handler
  
  encoder : H.264
  
  Stream #0:2(und): Data: none (mebx / 0x7862656D), 0 kb/s (default)
  
  Metadata:
  
  creation_time : 2016-02-03 05:25:18
  
  handler_name : Core Media Data Handler
  
  Stream #0:3(und): Data: none (mebx / 0x7862656D), 0 kb/s (default)
  
  Metadata:
  
  creation_time : 2016-02-03 05:25:18
  
  handler_name : Core Media Data Handler
  
  Unsupported codec with id 0 for input stream 2
  
  Unsupported codec with id 0 for input stream 3

  If latest version of ffmpeg (2.8) is used to auto rotate the video, can you please suggest me what option I need to add or remove from my final command.

• When compressing a set of images with libx264, why does frame rate affect final output size ?

  3 avril 2018, par jd20

  I’m using ffmpeg to encode a set of images as a short timelapse video, using libx264 codec. My first attempt, I encoded it at 30 FPS, using :

  ffmpeg -r 30 -pattern_type glob -i "*.jpg" -vcodec libx264 -crf 30 -pix_fmt yuv420p output.mp4

  With 60 frames, that gives me a 163 KB file that’s 2 seconds long. Then I realized I needed it to be slower, so I re-ran the same command, but changed -r to 2. Now I have a file that’s 30 seconds long, but the size jumped to 891 KB ! The video quality looks perceptually the same.

  How do I encode at a slower frame rate, without the final file size ballooning ?

  ---

  Notes : Some theories I had, and things I checked. First, to make sure ffmpeg wasn’t duplicating frames in the longer verison, I check the I/P/B counts. The 30 FPS file had :

  [libx264 @ 0x7f9b26001c00] frame I:1     Avg QP:30.67  size: 44649
  
  [libx264 @ 0x7f9b26001c00] frame P:15    Avg QP:31.19  size:  5471
  
  [libx264 @ 0x7f9b26001c00] frame B:44    Avg QP:31.45  size:   767

  The 2 FPS file had :

  [libx264 @ 0x7fcd32842200] frame I:1     Avg QP:21.29  size: 90138
  
  [libx264 @ 0x7fcd32842200] frame P:15    Avg QP:22.48  size: 33686
  
  [libx264 @ 0x7fcd32842200] frame B:44    Avg QP:26.29  size:  6674

  So, the I/P/B counts are identical, but the QP is much lower for the 2 FPS file. To offset, I tried increasing -crf for the 2 FPS file, to get about the same target size, but that just gave me a very blurry video (had to go to crf=40). I tried messing with -minrate, -maxrate, -bt, none helped. I’m guessing there is some x264 codec setting which is frame rate dependent, but I’m at a loss trying to figure out which one (from what I understand, constant bitrate is affected by frame rate but CRF should not be, but maybe I’m misunderstanding it.

• When compressing a set of images with libx264, why does frame rate affect final output size ?

  3 avril 2018, par jd20

  I’m using ffmpeg to encode a set of images as a short timelapse video, using libx264 codec. My first attempt, I encoded it at 30 FPS, using :

  ffmpeg -r 30 -pattern_type glob -i "*.jpg" -vcodec libx264 -crf 30 -pix_fmt yuv420p output.mp4

  With 60 frames, that gives me a 163 KB file that’s 2 seconds long. Then I realized I needed it to be slower, so I re-ran the same command, but changed -r to 2. Now I have a file that’s 30 seconds long, but the size jumped to 891 KB ! The video quality looks perceptually the same.

  How do I encode at a slower frame rate, without the final file size ballooning ?

  ---

  Notes : Some theories I had, and things I checked. First, to make sure ffmpeg wasn’t duplicating frames in the longer verison, I check the I/P/B counts. The 30 FPS file had :

  [libx264 @ 0x7f9b26001c00] frame I:1     Avg QP:30.67  size: 44649
  
  [libx264 @ 0x7f9b26001c00] frame P:15    Avg QP:31.19  size:  5471
  
  [libx264 @ 0x7f9b26001c00] frame B:44    Avg QP:31.45  size:   767

  The 2 FPS file had :

  [libx264 @ 0x7fcd32842200] frame I:1     Avg QP:21.29  size: 90138
  
  [libx264 @ 0x7fcd32842200] frame P:15    Avg QP:22.48  size: 33686
  
  [libx264 @ 0x7fcd32842200] frame B:44    Avg QP:26.29  size:  6674

  So, the I/P/B counts are identical, but the QP is much lower for the 2 FPS file. To offset, I tried increasing -crf for the 2 FPS file, to get about the same target size, but that just gave me a very blurry video (had to go to crf=40). I tried messing with -minrate, -maxrate, -bt, none helped. I’m guessing there is some x264 codec setting which is frame rate dependent, but I’m at a loss trying to figure out which one (from what I understand, constant bitrate is affected by frame rate but CRF should not be, but maybe I’m misunderstanding it.