[MPlayer-dev-eng] [PATCH] af_scale* command-line only

[Robert Juliano]

On Thu, Sep 06, 2007 at 02:53:01PM -0700, Scott Lamb wrote:
> I tried out your June 13th patch. [1] Is this the 
> latest version?

I did some work on it after that but haven't posted anything.
I wasn't getting much feedback from people who actually tried
it or found it useful.  So my new job got my attention.  When
I got back around to it, I implemented it for another framework.

> * on first run of "mplayer -af scalepitch=1.5 speed=1.5 file.avi", it
> crashed somewhere in audio decoding. Unfortunately, I had not compiled
> with --enable-debug, and when I did the error went away.

Yeah, if some piece of code overwrites af_scale* memory, it
will most likely crash.  I've noticed with newer revisions,
that some of my test files produce crashes.  I've haven't
looked into it yet.

> * I don't understand the point of scaletempo= or scalerate=.

scaletempo scales just tempo.  scalepitch scales just pitch.
scalerate scales both tempo and pitch (replicates -speed).

scaletempo does the magic and does what you want.  scalerate
exists to implement scalepitch.  That is: scalerate (both
tempo and pitch) - scaletempo (unscale tempo) = scalepitch.

Any two gets you the third.  So with a little algebra, and
we have what you did below.

> ** it seems to *increase* the pitch by the given factor, so when used 
> with -speed, the numbers need to be reciprocals to maintain the original 
> pitch. E.g., I am running it with the rather ugly command "mplayer -af 
> scalepitch=.76923076923076923076 -speed 1.3 file.avi". It would be more 
> convenient if I didn't have to use a calculator to generate the correct 
> command.

While this would do:
bash$ mplayer -af scalepitch=$( echo 1/1.3 | bc ) -speed 1.3 ...

I suggest:
mplayer -af scaletempo=1.3 -speed 1.3 ...

> ** an "-af scalepitch_auto" filter (like the "-af scaletempo_auto" you 
> had in the previous patch set) that follows my "[" and "]" keypresses 
> would be extremely useful. With it, people could take advantage of this 
> feature without even being conscious of it, which I think is the ideal 
> thing.

If they still patch, I would try the first three patches from
my earlier set *.  1 and 3 are essential.  You could also try
4, it automagically inserts scaletempo, so no need for the
commandline -af.  Otherwise just use 'mplayer -af scaletempo
filename' and then '[' ']' 'BS' to adjust the speed.

* http://lists.mplayerhq.hu/pipermail/mplayer-dev-eng/2007-June/052312.html

I know I have some new patches lying around.  I'll see if I
can get them posted within the next week or so.

ciao,
robert