user24293: I'm trying to convert a webm file that has a transparent background to an mp4 file. Mp4 doesn't have transparency so I'm trying to using this color: #D9DADB. How can I make this conversion happen with a single command in ffmpeg?
I've tried the following command and I seem to get a black background instead of a gray one: 
ffmpeg -f lavfi -i color=c=0xD9DADB -i 123.webm 123.mp4


user1871: The native VP8/9 decoders don't support transparency, so a) you'll have to force a decoder, b) the way to change transparent pixels is to overlay the video onto the color.
ffmpeg -c:v libvpx -i 123.webm -f lavfi -i color=c=0xD9DADB,format=rgb24
       -filter_complex "[1][0]scale2ref[bg][vid];[bg][vid]overlay=format=rgb:shortest=1,setsar=1"
       -pix_fmt yuv420p -c:a copy 123.mp4


24293: <p>I'm trying to convert a webm file that has a transparent background to an mp4 file. Mp4 doesn't have transparency so I'm trying to using this color: #D9DADB. How can I make this conversion happen with a single command in ffmpeg?</p>

<p>I've tried the following command and I seem to get a black background instead of a gray one: </p>

<pre><code>ffmpeg -f lavfi -i color=c=0xD9DADB -i 123.webm 123.mp4
</code></pre>
 1871: <p>The native VP8/9 decoders don't support transparency, so a) you'll have to force a decoder, b) the way to change transparent pixels is to overlay the video onto the color.</p>

<pre><code>ffmpeg -c:v libvpx -i 123.webm -f lavfi -i color=c=0xD9DADB,format=rgb24
       -filter_complex "[1][0]scale2ref[bg][vid];[bg][vid]overlay=format=rgb:shortest=1,setsar=1"
       -pix_fmt yuv420p -c:a copy 123.mp4
</code></pre>
