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• 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.

• Not able to run the final step of running supervisord for plumi

  1er avril 2021, par manic_startup

  on the github page https://github.com/plumi/plumi.app
I am on the final step of Step 6. see below section

  


  =========================

  


  Step 6 : start supervisord
With plumi buildout having finished and ffmpeg installed on our system, it's time to run supervisord :

  


  root@user :/home/plumi.app# ./bin/supervisord

  


  ========================

  


  When I type in the above on CentOS 7 it says "bash : ./bin/supervisord : No such file or directory

  


  I had to change some things in step 5 "Step 5 Install ffmpeg" for the centos section there are two urls in that section pointing to some repos. They did not work so I had to find some other ones on the Internet. The ones I used where.
https://dl.fedoraproject.org/pub/epel/7/x86_64/Packages/e/epel-release-7-13.noarch.rpm

  


  http://ftp.riken.jp/Linux/atrpms/el7-x86_64/atrpms/stable/atrpms-repo-7-7.el7.x86_64.rpm

  


  The first one looks the same but it is different also the only release available was 7-13 so i used that.
The second one is a different url but the file is the same.

  


  also in that section is asks to edit /etc/yum.repos.d/atrpms.repo. It asks to change the base URL to a URL similar to the what is asks when it asked to download from the second repo above. Obviously that url is different now so I changed it to this instead.
http://ftp.riken.jp/Linux/atrpms/el$releasever-$basearch/atrpms/stable/

  


  After this I asks to install ffmpeg this did not work so I used the below guide
https://linuxize.com/post/how-to-install-ffmpeg-on-centos-7/

  


  Then came the section 6 to install supervisord as explained at the start this did not work. Now im stuck !

  


  I have also realised that when I get to the following command in step 4.

  


  ./bin/python bootstrap.py && ./bin/buildout -v

  


  It fails and says "Error : couldn't find distribution for 'hachoir-parser==1.3.4' and bombs out. I have tried to find this file but cant install it and dont know if i even have the correct file. not sure what to do.