user25202: multiply should result in a darker image according to this website. However every multiply options with input that I'm using resulted in darker green videos instead of layering it with colour that I use for layering.
Many people refer that as format issue and resolved by using format=rgba options, however in my case there I'm still stuck.
FFMPEG command :
ffmpeg -i red.jpg -i car.mp4 -y -filter_complex [0][1]scale2ref[a][b];[a]setdar=1/1[c];[b]setdar=1/1[d];[c][d]blend=all_mode=multiply:all_opacity=1[out];[out]eq=contrast=2:brightness=0.5[ckv] -map [ckv] output.mp4

with format=rgba
ffmpeg -i red.jpg -i car.mp4 -y -filter_complex [0][1]scale2ref[a][b];[a]setdar=1/1[c];[b]setdar=1/1,format=rgba[d];[c][d]blend=all_mode=multiply:all_opacity=1[out];[out]eq=contrast=2:brightness=0.5[ckv] -map [ckv] output.mp4

assets in case someone want to try it.
- Images
- Videos
FFMPEG version 4.1

user-1: Your command is wrong, if you enable debug log messages, you would notice that yuv formats are still being used.
You need to put format=rgba filter to all inputs and outputs of blend filter to make it work as you want.

25202: <p>multiply should result in a darker image according to <a href="https://www.cairographics.org/operators/" rel="nofollow noreferrer">this website</a>. However every <code>multiply</code> options with input that I'm using resulted in darker <strong>green</strong> videos instead of layering it with colour that I use for layering.</p>

<p>Many people refer that as format issue and resolved by using <code>format=rgba</code> options, however in my case there I'm still stuck.</p>

<p>FFMPEG command :</p>

<pre><code>ffmpeg -i red.jpg -i car.mp4 -y -filter_complex [0][1]scale2ref[a][b];[a]setdar=1/1[c];[b]setdar=1/1[d];[c][d]blend=all_mode=multiply:all_opacity=1[out];[out]eq=contrast=2:brightness=0.5[ckv] -map [ckv] output.mp4
</code></pre>

<p>with <code>format=rgba</code></p>

<pre><code>ffmpeg -i red.jpg -i car.mp4 -y -filter_complex [0][1]scale2ref[a][b];[a]setdar=1/1[c];[b]setdar=1/1,format=rgba[d];[c][d]blend=all_mode=multiply:all_opacity=1[out];[out]eq=contrast=2:brightness=0.5[ckv] -map [ckv] output.mp4
</code></pre>

<p>assets in case someone want to try it.
- <a href="https://i.ibb.co/smSGGwW/red.jpg" rel="nofollow noreferrer">Images</a>
- <a href="https://www.pexels.com/video/car-driving-along-the-dessert-highway-1572342/" rel="nofollow noreferrer">Videos</a></p>

<p>FFMPEG version 4.1</p>
 -1: <p>Your command is wrong, if you enable debug log messages, you would notice that yuv formats are still being used.
You need to put <code>format=rgba</code> filter to all inputs and outputs of blend filter to make it work as you want.</p>
