Answers.Body: <p>Did you actually get every second frame? My impression is that you got every frame, but you halved the framerate. Therefore, the length of the video in seconds is twice as long for the first compared to the second, and assuming equal rate controls (e.g. 1 megabit per second), the twice-as-long-file will thus be approximately twice as big, which is what you got.</p>
  
Answers.ContentLicense: CC BY-SA 3.0
Answers.CreationDate: 2015-11-03T18:34:24.013Z
Answers.Text: That may be the case. What would be the correct command.
Answers.UserDisplayName: student
Answers.ContentLicense: CC BY-SA 3.0
Answers.CreationDate: 2015-11-04T01:17:06.267Z
Answers.Text: -v:b 500 for the first, and -v:b 1000 for the second. If my hypothesis is correct, using double bitrate for the second should give exactly identical quality for both videos (i.e. they should look visually indistinguishable, other than them being twice as slow/fast).
Answers.UserDisplayName: Ronald S. Bultje
Answers.ContentLicense: CC BY-SA 3.0
Answers.CreationDate: 2015-08-10T18:58:27.430Z
Answers.LastActivityDate: 2015-08-10T18:58:27.430Z
Answers.UserDisplayName: Ronald S. Bultje
Body: <p>I just did:</p>
  
  <p><code>ffmpeg -i inputfile -r 30 -vcodec libx264 -an -s hd480 output_30.mp4</code></p>
  
  <p>and</p>
  
  <p><code>ffmpeg -i inputfile -vcodec libx264 -an -s hd480 output_60.mp4</code></p>
  
  <p>on a 60fps file. </p>
  
  <p>Why is the second file 27 MB and the first file 49 MB despite the fact that the first file contains only every second frame?</p>
  
Comments.ContentLicense: CC BY-SA 3.0
Comments.CreationDate: 2015-07-27T03:14:10.580Z
Comments.Text: Please show the complete console output from each command.
Comments.UserDisplayName: llogan
Tags: <ffmpeg>
Title: ffmpeg reducing 60fps to 30fps, but file size is larger
UserDisplayName: student
ThreadText: # ffmpeg reducing 60fps to 30fps, but file size is larger
  
  (Asked by: username_0 on 2015-07-26)
  
  I just did:
  
  `ffmpeg -i inputfile -r 30 -vcodec libx264 -an -s hd480 output_30.mp4`
  
  and
  
  `ffmpeg -i inputfile -vcodec libx264 -an -s hd480 output_60.mp4`
  
  on a 60fps file.
  
  Why is the second file 27 MB and the first file 49 MB despite the fact that the first file contains only every second frame?
  
  **Tags:** ffmpeg
  
  > **Comments:**
  > **username_1**: Please show the complete console output from each command.  
  
  ---
  
  ## 1 answers
  
  ### Answer by username_2 on 2015-08-10. Score: 2
  
  Did you actually get every second frame? My impression is that you got every frame, but you halved the framerate. Therefore, the length of the video in seconds is twice as long for the first compared to the second, and assuming equal rate controls (e.g. 1 megabit per second), the twice-as-long-file will thus be approximately twice as big, which is what you got.
  
  > **Comments:**
  > **username_0**: That may be the case. What would be the correct command.  
  > **username_2**: -v:b 500 for the first, and -v:b 1000 for the second. If my hypothesis is correct, using double bitrate for the second should give exactly identical quality for both videos (i.e. they should look visually indistinguishable, other than them being twice as slow/fast).  
  
  ---
  
  