user9097: I want to extend basic usage of watermark and put it under the video.
That means. I have input video 720x480 and image 720x20.
On output i want to have video 720x500 where video aspect is preserved and positioned to top and image is added to bottom.
input video
|--------------------------|
|                          |
|                          |
|                          |
|          720*480         |
|                          |
|                          |
|                          |
|--------------------------|

input image
|--------------------------|
|          720x20          |
|--------------------------|

output video
|--------------------------|
|                          |
|                          |
|                          |
|          720*480         |
|                          |
|                          |
|                          |
|--------------------------|
|          720x20          |
|--------------------------|

Thanks

user6685: I think it's probably easier to combine (stack) a full dimension background image (720x500px) with your video in ffmpeg instead of adding the 20px footer to the video. You can simply use the overlay filter for this:
ffmpeg \
    -loop 1 -i 720x500.jpg \
    -i 720x480.mp4 \
    -filter_complex overlay=0:0 \
    -t 0:01.48 \ 
    out.m4v

Note: In this example you have to set the duration of your output video manually with -t parameter.

If you don't want to specify the duration you can use shortest flag within the filter if you use -loop 1 as @LordNeckbeard mentioned in the comments below:
ffmpeg \
    -loop 1 -i 720x500.jpg \
    -i 720x480.mp4 \
    -filter_complex "overlay=0:0:shortest=1" \
    out.m4v


user1760: Use the vstack filter:

ffmpeg -i video.mp4 -i image.png -filter_complex vstack output.mp4

If the image is not the same width as the video then resize it with the scale filter:
ffmpeg -i video.mp4 -i image.png -filter_complex "[1:v]scale=320:-1[bottom];[0:v][bottom]vstack" output.mp4


9097: <p>I want to extend basic usage of watermark and put it under the video.
That means. I have input video 720x480 and image 720x20.
On output i want to have video 720x500 where video aspect is preserved and positioned to top and image is added to bottom.</p>

<p>input video</p>

<pre><code>|--------------------------|
|                          |
|                          |
|                          |
|          720*480         |
|                          |
|                          |
|                          |
|--------------------------|
</code></pre>

<p>input image</p>

<pre><code>|--------------------------|
|          720x20          |
|--------------------------|
</code></pre>

<p>output video</p>

<pre><code>|--------------------------|
|                          |
|                          |
|                          |
|          720*480         |
|                          |
|                          |
|                          |
|--------------------------|
|          720x20          |
|--------------------------|
</code></pre>

<p>Thanks</p>
 6685: <p>I think it's probably easier to <em>combine (stack) a full dimension background image (720x500px) with your video</em> in ffmpeg instead of adding the 20px footer to the video. You can simply use the <code>overlay filter</code> for this:</p>

<pre><code>ffmpeg \
    -loop 1 -i 720x500.jpg \
    -i 720x480.mp4 \
    -filter_complex overlay=0:0 \
    -t 0:01.48 \ 
    out.m4v
</code></pre>

<p><strong>Note:</strong> In this example you have to set the duration of your output video manually with <code>-t</code> parameter.</p>

<hr>

<p>If you <em>don't want to specify the duration</em> you can use <code>shortest</code> flag within the filter if you use <code>-loop 1</code> as @LordNeckbeard mentioned in the comments below:</p>

<pre><code>ffmpeg \
    -loop 1 -i 720x500.jpg \
    -i 720x480.mp4 \
    -filter_complex "overlay=0:0:shortest=1" \
    out.m4v
</code></pre>
 1760: <p>Use the <a href="http://ffmpeg.org/ffmpeg-filters.html#vstack" rel="nofollow noreferrer">vstack filter</a>:</p>

<p><img src="https://i.stack.imgur.com/FuIdO.png" alt="hstack"></p>

<pre><code>ffmpeg -i video.mp4 -i image.png -filter_complex vstack output.mp4
</code></pre>

<p>If the image is not the same width as the video then resize it with the <a href="http://ffmpeg.org/ffmpeg-filters.html#scale" rel="nofollow noreferrer">scale filter</a>:</p>

<pre><code>ffmpeg -i video.mp4 -i image.png -filter_complex "[1:v]scale=320:-1[bottom];[0:v][bottom]vstack" output.mp4
</code></pre>
