[FFmpeg-user] No pixel format specified - meaning of yuv420p?

[Lou]

On Thu, Dec 1, 2016, at 03:00 PM, MRob wrote:
> I'm exporting a video from an older Adobe Elements (Windows) with 
> intention to put it on the web (both H.264 and VP8). I exported using 
> Adobe's "DV AVI" which appears to be the most unmolested output format

DV is not a good choice: it's lossy and will mess up your width, height,
aspect ratio, etc. Install UT video. UT video is a free and open
compressed lossless format that works well as an intermediate format:

http://umezawa.dyndns.info/archive/utvideo/?C=M;O=D

Then restart Elements and export using that. Make sure Elements doesn't
change the width, height, frame rate, etc (I recall Adobe Media Encoder
doing that often). Finally, re-enode the intermediate file with ffmpeg.

[...]
> But from reading that mailing list post and the error message text, it 
> sounds like adding "-pix_fmt yuv420p" affects the output. I do not need 
> to retain compatibility with terribly old devices (though I am using 
> baseline level 3.0), so I wanted to ask if there is a better way to 
> handle conversion in this case.

You'll need yuv420p. Most non-FFmpeg based players and various devices
don't support anything else.

> There is also an option in Elements to export MPEG H.264 ("1080i 25" or 
> "1080i 30", providing profiles main/high, levels 4/4.1, default 1 pass 
> bitrate of 20, etc), but I don't understand all their settings and I 
> trust ffmpeg to do a better job and I don't want to encode twice if 
> possible.

I probably wouldn't use it either.

> Here are the options I'm using for H.264 conversion:
> -movflags +faststart -codec:v libx264 -preset veryslow -profile:v 
> baseline -level:v 3.0 -codec:a aac

You can omit -profile and -level if you don't care to support old
devices, otherwise keep it if you want widest compatibility.

> For VP8 conversion, I only get the first warning:
> Guessed Channel Layout for Input Stream #0.1 : stereo
> Otherwise, it completes without any errors.

Ignore.