[FFmpeg-user] Tips on compressing videos created by GoPro

[Moritz Barsnick]

(Kieran's mail passed mine. :-))

On Thu, Oct 19, 2017 at 07:33:34 -0600, Andrey Goreev wrote:
> I have noticed that I get a bunch of warnings when compressing videos made 
> by a GoPro camera.

> "Unsupported codec with id 0 for input stream 2"

Let me guess: The files may hold something like geo-positions encoded
as subtitles, or a timecode track, or something similarly strange or
proprietary, which ffmpeg cannot handle. This stream is dropped (but
probably useless to you, unless you miss something in the resulting
file).

> FFmpeg:
> "No pixel format specified, yuvj420p for H.264 encoding chosen.
> Use -pix_fmt yuv420p for compatibility with outdated media players.  "

It means exactly that. Probably (we'll know when we see your complete
console output) your input was using colorspace yuvj420p, and ffmpeg
doesn't change this unless you tell it to. This resulting file may be
fine in VLC, as you point out, but perhaps some fool is using Windows
Media Player, or some hardware "media player" which doesn't support
this. For broader compatibility, follow the recommended hint. If you
don't care, because VLC is fine, then just don't bother. (Some
developers are in favor of removing this warning. It's reason is that
there have been many "bug" reports of ffmpeg creating files which had
"only black output" or the likes, while it was just a compatibility
problem of the players.)

Cheers,
Moritz