You can specify multiple inputs to FFMPEG and mix them into a single output. I understand the basics of this, for example:
ffmpeg -i vid1.mp4 -i vid2.mp4 [commands] output.mp4
What I can't figure out is how I can specify different commands for each input. For example, I have the following I'm trying to do:
ffmpeg -i vid1.m2t -i vid2.mp4 -map 0:a -filter_complex "[0:v:0][1:v:0]vstack=inputs=2" -crf 24 -c:a aac -b:a 128k -ac 1 -movflags +faststart output.mp4
vid1.m2t is a 1440 anamorphic hdv mpeg stream, and
vid2.mp4 is a regular 1920 h.264. Using
-filter_complex "[0:v:0][1:v:0]vstack=inputs=2" I'm trying to stack vid1 on top of vid2, but I get the error that says it can't proceed because the two videos are not the same width. Well, yes, except in display the m2t is actually 1920 wide, not 1440.
When I'm converting just the hdv by itself, I use
-filter_complex "scale=1920:1080,setsar=1" to ensure square pixels. I know that works well, but how can I incorporate that into this vstack command? If I put it in with the other I get errors. I've tried a variety of different ways, including before the input (thinking that would make ffmpeg apply it only to the input before sending it to the other commands for output), but they all make errors.
Additionally, I wonder if the
-crf 24 command can be specified for each input. When converting individually the m2t needs to be at 24 or less, or it looks bad, while the mp4 can be as high as 30. I might be misunderstanding what vstack does, but I would think that if I can tell ffmpeg to give different attention to quality for each input would lessen file size.
I have the same issue with
hstack. FFMPEG will render the output, but the m2t file comes out 1440 wide, therefore skewed. So the total video width is 3360 wide, instead of 3840.
Maybe more specific to this exact problem, how can I use vstack or hstack when the inputs have different dimensions?