easier access to (ex: libx264) presets available

[Roger Pack]

Hello. Currently the "help" output refers one to the binary x264 (which may not be available, ex: on windows) for a list of presets. It would be convenient to have some way to enumerate them without needing a second executable.
ref: ​https://lists.ffmpeg.org/pipermail/ffmpeg-user/2012-June/007365.html
Or auto-add them to docu, etc.

[Cigaes]

In the laetst Git version, setting an invalid preset or tune will print the list:

[libx264 @ 0x99fea0] Error setting preset/tune help/(null).
[libx264 @ 0x99fea0] Possible presets: ultrafast superfast veryfast faster fast medium slow slower veryslow placebo
[libx264 @ 0x99fea0] Possible tunes: film animation grain stillimage psnr ssim fastdecode zerolatency

Note that help or list are invalid, and thus will have that result.

If this is acceptable to you, you can close the bug.

[Carl Eugen Hoyos]

Afaict, this was fixed by Nicolas, please reopen if the solution is insufficient.

[Roger Pack]

Thanks this is great!
A few minor additions that might be helpful:
Since there are some "file based" presets that aren't listed (​https://github.com/FFmpeg/FFmpeg/tree/master/presets ) the output text might be better served as "Possible tunes (doesn't include external files):" or something like that.

Also a similar help output message for bad h264 profiles would be convenient, as well, but not necessary. Thanks!

[Cigaes]

Replying to rogerdpack:

Since there are some "file based" presets that aren't listed (​https://github.com/FFmpeg/FFmpeg/tree/master/presets ) the output text might be better served as "Possible tunes (doesn't include external files):" or something like that.

I am afraid this is difficult: -vpre and its presets is specific to the ffmpeg command-line tool, while this error message comes from the library, and could appear in another application that does not have that kind of presets.

Also a similar help output message for bad h264 profiles would be convenient, as well, but not necessary. Thanks!

Patch for that posted:
​http://ffmpeg.org/pipermail/ffmpeg-devel/2012-July/128463.html
It will be possible to fix your name in the commit message if you want until this is pushed in the official repository.

[Roger Pack]

Ok that makes sense (changing the error message to say "Possible internal tunes" might still be a small improvement.

Patch looks great.
Thanks for doing that!
-roger-