<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>

CC BY-SA 3.0
2014-01-20T06:40:13.637Z
Will give you 50 rep for this when the system permits me to.
v010dya
CC BY-SA 3.0
2014-01-20T06:22:58.973Z
2014-01-20T06:22:58.973Z
stib
<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>

CC BY-SA 3.0
2013-11-08T15:51:18.537Z
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.
v010dya
CC BY-SA 3.0
2013-11-08T00:17:11.017Z
2013-11-08T00:17:11.017Z
audiomason
<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>

CC BY-SA 3.0
2013-11-04T14:15:11.427Z
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.)
AJ Henderson
CC BY-SA 3.0
2013-11-04T14:22:12.767Z
@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.
v010dya
CC BY-SA 3.0
2013-11-04T14:25:30.560Z
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.
AJ Henderson
<video><libav>
Deinterlace by dropping even lines from command line
v010dya
# 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**: @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.  
> **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.  

---

