[FFmpeg-user] overlay w/librtmp

[Tom Evans]

On Mon, Mar 26, 2012 at 6:19 PM, Scott Freeman <scottf at tvw.org> wrote:
> Tom, thanks for the clarification. Like I mentioned, I thought it would be
> a stretch to call it a bug. And you confirmed my guess on how
> "copy" worked, thank you.
>
> I am curious though about what you said and this may be a topic for another
> thread. Why couldn't ffmpeg be able to detect the input video information
> and create a "similar" output string to essentially copy the inputs
> settings? I could surely do that or something similar with a script and
> some program logic to generate a output string before starting the encode.
> I think it would make for a good feature built-in, especially when users
> sometimes are just re-encoding a video to do effects and overlays and such.
> Am I way off here?
>
> Thanks again Tom, for taking the time to reply to my post.
>
> Cheers,
> Scott

Please don't top post, people will get angry.

Certain parameters - the dimensions of the video, the colourspace, the
codec used, the average bitrate - can be deduced, and ffmpeg can
detect those.

What about things like whether the video was 2 or 3 pass encoded, how
will it deduce that? How about codec/encoder specific things - if
x264, what preset to use, ultrafast or ultraslow? Did the original
have an x264 tuning (film, cartoon, etc).

If you are planning to overlay a logo on videos, it would be better to
do so before you do the lossy encoding. I don't know if that is
appropriate for you, maybe you start with quite lossy videos already?

Cheers

Tom