Answers.Body: <p>Since drawbox doesn't support time reference, you need to use a workaround</p>
  
  <pre><code>ffmpeg -y -loop 1 -t 5 -i img001.jpg
    -filter_complex "color=red@0.5:s=Wx100[c];
                     [0][c]overlay='-W+300*t':0"
    -y out.mp4
  </code></pre>
  
  <p>A color source is created equal to the final size of the box you wanted to draw i.e. image width (W) x 100. Then it is overlaid on the image and animated so that it starts revealing at the rate of <code>300*t</code>.</p>
  
Answers.ContentLicense: CC BY-SA 3.0
Answers.CreationDate: 2018-02-23T10:49:49.587Z
Answers.Text: It Works! I just did this modification to avoid the rectangle to "go away" from the screen heheh
  `/usr/bin/ffmpeg -y -loop 1 -t 5 -i source/img001.jpg -filter_complex 
  "color=red@0.5:s=1024x100[c];[0][c]overlay='if(lte(-1024+1500*t,0),-1024+1500*t,0)':0" -t 10 out.mp4`
Answers.UserDisplayName: GFCoder977
Answers.ContentLicense: CC BY-SA 3.0
Answers.CreationDate: 2018-02-23T05:54:36.047Z
Answers.LastActivityDate: 2018-02-23T05:54:36.047Z
Answers.UserDisplayName: Gyan
Body: <p>I'd like to apply a dynamic drawbox before a drawtext, for example, with a fixed Y , X and H but with a dynamic W.</p>
  
  <p>This is a trivial example: </p>
  
  <pre><code>/usr/bin/ffmpeg -y -loop 1 -t 5 -i img001.jpg -vf drawbox=x=0:y=0:w=t*300:h=100:color=red@0.5 -y out.mp4
  </code></pre>
  
  <p>I expect to see a rectangle with the base width that increase with the time; it does not work, the box width is alwais fixed.</p>
  
  <p>Is it possible to create a dynamic drawbox? if not, is there an alternative?</p>
  
Comments.ContentLicense: CC BY-SA 3.0
Comments.CreationDate: 2018-02-21T17:37:58.493Z
Comments.Text: drawbox doesn't support time reference. What are you trying to do?
Comments.UserDisplayName: Gyan
Comments.ContentLicense: CC BY-SA 3.0
Comments.CreationDate: 2018-02-22T14:03:06.547Z
Comments.Text: mmm I'd like to draw a rectangular shape, with some opacity,  that comes from one side and fill the entire witdh of the video. Then the text appear over it, from one side for example. A kind of graphic  introduction for the text.
Comments.UserDisplayName: GFCoder977
Tags: <ffmpeg>
Title: ffmpeg- dynamic drawbox
UserDisplayName: GFCoder977
ThreadText: # ffmpeg- dynamic drawbox
  
  (Asked by: username_0 on 2018-02-21)
  
  I'd like to apply a dynamic drawbox before a drawtext, for example, with a fixed Y , X and H but with a dynamic W.
  
  This is a trivial example:
  
  ```
  /usr/bin/ffmpeg -y -loop 1 -t 5 -i img001.jpg -vf drawbox=x=0:y=0:w=t*300:h=100:color=red@0.5 -y out.mp4
  
  ```
  
  I expect to see a rectangle with the base width that increase with the time; it does not work, the box width is alwais fixed.
  
  Is it possible to create a dynamic drawbox? if not, is there an alternative?
  
  **Tags:** ffmpeg
  
  > **Comments:**
  > **username_1**: drawbox doesn't support time reference. What are you trying to do?  
  > **username_0**: mmm I'd like to draw a rectangular shape, with some opacity,  that comes from one side and fill the entire witdh of the video. Then the text appear over it, from one side for example. A kind of graphic  introduction for the text.  
  
  ---
  
  ## 1 answers
  
  ### Answer by username_1 on 2018-02-23. Score: 3
  
  Since drawbox doesn't support time reference, you need to use a workaround
  
  ```
  ffmpeg -y -loop 1 -t 5 -i img001.jpg
    -filter_complex "color=red@0.5:s=Wx100[c];
                     [0][c]overlay='-W+300*t':0"
    -y out.mp4
  
  ```
  
  A color source is created equal to the final size of the box you wanted to draw i.e. image width (W) x 100. Then it is overlaid on the image and animated so that it starts revealing at the rate of `300*t`.
  
  > **Comments:**
  > **username_0**: It Works! I just did this modification to avoid the rectangle to "go away" from the screen heheh `/usr/bin/ffmpeg -y -loop 1 -t 5 -i source/img001.jpg -filter_complex  "color=red@0.5:s=1024x100[c];[0][c]overlay='if(lte(-1024+1500*t,0),-1024+1500*t,0)':0" -t 10 out.mp4`  
  
  ---
  
  