Answers.Body: <p><code>ffmpeg -i input -vf field,scale=123:456 output</code> will do the trick, where 123:456 is your x:y frame dimensions for the output. The field filter just chucks away the fields it doesn't use. Documention on the field filter <a href="http://ffmpeg.org/ffmpeg-all.html#field" rel="nofollow">here</a>. Note that you'll need extra stuff in the command to get good results - e.g. you'll probably want to specify codec details and so on.</p>
  
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Answers.CreationDate: 2014-01-20T06:40:13.637Z
Answers.Text: Will give you 50 rep for this when the system permits me to.
Answers.UserDisplayName: v010dya
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Answers.UserDisplayName: stib
Answers.Body: <p>You could use ffmpeg:</p>
  
  <pre><code>ffmpeg -i input -vf framestep=2 output
  </code></pre>
  
  <p>This will output every second frame.</p>
  
Answers.ContentLicense: CC BY-SA 3.0
Answers.CreationDate: 2013-11-08T15:51:18.537Z
Answers.Text: That doesn't actually do what is expected with the progressive video. The result is still the same vertical resolution, so it doesn't drop unneeded lines.
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Answers.UserDisplayName: audiomason
Body: <p>I want to make an interlaced video with 50fps into a 25fps progressive, in the process i'm also reducing the size of the frame. Currently i am using avconv and there are deinterlacing options, however, they are not documented. So what i am afraid of is that they will actually start bleeding information i am trying to drop into the frames that i am trying to keep.</p>
  
  <p>The only tool that i have found, that does a documented drop of even/odd frames is a plugin for AVIDemux, which unfortunately does not export into Ogg or even encode into Theora. When i attempt to dump into Huff codec (to not introduce quality loss due to reencoding) it demands that i split files at 4 GiB. So i can only use it for small videos.</p>
  
  <p>Is there another tool that can help me?</p>
  
Comments.ContentLicense: CC BY-SA 3.0
Comments.CreationDate: 2013-11-04T14:15:11.427Z
Comments.Text: You could always do the 4gigabyte split and then cut them back together after (assuming Huff codec supports append operations without re-encoding, I'm not familiar with that particular codec.)
Comments.UserDisplayName: AJ Henderson
Comments.ContentLicense: CC BY-SA 3.0
Comments.CreationDate: 2013-11-04T14:22:12.767Z
Comments.Text: @AJHenderson It is a possibility, and i was already looking at that, but it's a hack. I think i would rather try to figure out the avlib's code and create a 'drop-deinterlacer', but i was hoping that something like that already exists.
Comments.UserDisplayName: v010dya
Comments.ContentLicense: CC BY-SA 3.0
Comments.CreationDate: 2013-11-04T14:25:30.560Z
Comments.Text: yeah, makes sense.  I unfortunately have near 0 experience with AVIDemux or avlib.  I'm an Adobe/Windows guy, just a few little things when I was working on writing programs to work with video.
Comments.UserDisplayName: AJ Henderson
Tags: <video><libav>
Title: Deinterlace by dropping even lines from command line
UserDisplayName: v010dya
ThreadText: # Deinterlace by dropping even lines from command line
  
  (Asked by: username_0 on 2013-11-04)
  
  I want to make an interlaced video with 50fps into a 25fps progressive, in the process i'm also reducing the size of the frame. Currently i am using avconv and there are deinterlacing options, however, they are not documented. So what i am afraid of is that they will actually start bleeding information i am trying to drop into the frames that i am trying to keep.
  
  The only tool that i have found, that does a documented drop of even/odd frames is a plugin for AVIDemux, which unfortunately does not export into Ogg or even encode into Theora. When i attempt to dump into Huff codec (to not introduce quality loss due to reencoding) it demands that i split files at 4 GiB. So i can only use it for small videos.
  
  Is there another tool that can help me?
  
  **Tags:** video, libav
  
  > **Comments:**
  > **username_1**: You could always do the 4gigabyte split and then cut them back together after (assuming Huff codec supports append operations without re-encoding, I'm not familiar with that particular codec.)  
  > **username_0**: @username_1 It is a possibility, and i was already looking at that, but it's a hack. I think i would rather try to figure out the avlib's code and create a 'drop-deinterlacer', but i was hoping that something like that already exists.  
  > **username_1**: yeah, makes sense.  I unfortunately have near 0 experience with AVIDemux or avlib.  I'm an Adobe/Windows guy, just a few little things when I was working on writing programs to work with video.  
  
  ---
  
  ## 2 answers
  
  ### Answer by username_2 on 2014-01-20. Score: 1 | Accepted answer
  
  `ffmpeg -i input -vf field,scale=123:456 output` will do the trick, where 123:456 is your x:y frame dimensions for the output. The field filter just chucks away the fields it doesn't use. Documention on the field filter [here](http://ffmpeg.org/ffmpeg-all.html#field). Note that you'll need extra stuff in the command to get good results - e.g. you'll probably want to specify codec details and so on.
  
  > **Comments:**
  > **username_0**: Will give you 50 rep for this when the system permits me to.  
  
  ---
  
  ### Answer by username_3 on 2013-11-08. Score: 0
  
  You could use ffmpeg:
  
  ```
  ffmpeg -i input -vf framestep=2 output
  
  ```
  
  This will output every second frame.
  
  > **Comments:**
  > **username_0**: That doesn't actually do what is expected with the progressive video. The result is still the same vertical resolution, so it doesn't drop unneeded lines.  
  
  ---
  
  