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I am using Blender 3.1.2.

I want to render an animation with a transparent background.

I have Transparent checked in the Render Properties panel and in the Render Output panel I have file format FFmpeg video MPEG-4 or Quicktime selected. There is no RGBA option for Color. Only BW and RGB.

Every web post I've seen tells you select RGBA but this version of Blender doesn't seem to have it.

How else can I render an MP4 video with transparent background?

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  • $\begingroup$ You need to select a video format that supports alpha channel. Simple as that. It's the same for pictures. PNG has it, JPEG doesn't. Try one of the formats using webm-containers, like VP9, and you are good to go. $\endgroup$
    – Num Lock
    Commented May 11, 2022 at 5:40

2 Answers 2

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In addition to @Christopher Bennett's answer, but I'd like to point out that, while what you want is possible, it isn't the common practice in the industry for quite a bunch of reasons that everyone rendering anything from a CGI software should know about.

There is quite a clear distinction between what I like to call "production" and "delivery" formats. Production one's focus on being efficient, carry more data and be practical to use in production. While delivery formats often aim only to be lightweight at the cost of data or comply to old technical norms.
As long as you are doing anything other than making your final file that will be sent anywhere, you shouldn't use "delivery" formats. That includes most video formats, and most of the picture formats random people are familiar with (png, jpeg, gif).

While you can use an alpha output in a video, I'd suggest you don't use a video output at all unless you can't do otherwise or if it's a final export to be sent to a client or on the internet, and you have to comply to the target's needs.

Rendering anything into a video file is quite rare in production, for several reasons. Video encoding and decoding takes time and computing power (which are precious resources when rendering already), video files are way less versatile, more prone to break, harder to transfer, impossible to fix a messed up frame, impossible to resume if your render crashed, ... The list goes on.

Most of the time, productions will render into picture files, EXR or targa raw. Because they are fast to read and write, faster to transport, support alpha and higher bit depths and even render passes for EXR, allow redoing any portion of frames you want or resume a crashed render job, can carry lots of data at a small file size, ...

Interesting to read:

Once you are done making any editing you needed on your product, then you can output a video file, that can be compressed as you like.

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Unfortunately, alpha only has limited support in output formats due to compression factors. You can get alpha for an MPEG-4 container by using FFmpeg video codec format#1 as a codec (I know, it's a drag H.264 is not supported).

Codec

Documentation - https://docs.blender.org/manual/en/latest/files/media/video_formats.html

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