[FFmpeg-user] Simultaneous two-pass?

[Carl Eugen Hoyos]

Jesse Gordon <tojesseg <at> gmail.com> writes:

> >> But I suppose there is a limit to how far ahead
> >> bandwidth can be borrowed.
> >
> > Why do you think so?
> > I don't think it is true in the general case.
> 
> Oh, I just figured that the whole point of fixed rate 
> encoding was for streaming over a limited bandwidth 
> connection to a device that may or may not have a large buffer.

No, the original idea was to fit a video of a given length 
exactly on one CD (or DVD) with the best possible over-all 
quality.

What you want is one-pass encoding with some options 
(see other answers).

[...]

> >> I have 8 cores in my CPU and I did notice that ffmpeg
> >> was using about "160%" which means almost 2 cores.
> >> However, idle was still around 80%,
> > Play with different values for -threads
> > And note that not all encoders and not
> > all decoders support multi-threading.
> >
> I tried a few -threads options and nothing seemed to change 
> anything. It could be that the flv encoder doesn't support 
> threads.

Correct, see ffmpeg -encoders

> But that's OK because whenever a user uploads a video, it 
> has to be converted into half a dozen different sizes and 
> rates to accomodate viewers with different internet speeds, 
> so I can just launch several instances in parallel.

I suspect this should be (significantly?) faster if done 
in one FFmpeg instance.

Carl Eugen