Improve x264, vorbis and theora codecs

[tahajahangir]

Added quality option for x264, vorbis and theroa codecs and preset option for x264.

Also removed confusing unnecessary x264 options. (It's better to use presets) From http://ffmpeg.org/trac/ffmpeg/wiki/x264EncodingGuide:

You can overwrite default preset settings with the x264opts option or by using the libx264 private options (see libx264 AVOptions in ffmpeg -h full). This is not recommended unless you know what you are doing. The presets were created by the x264 developers and tweaking values to get a better output is usually a waste of time.

[senko]

Looks good in theory, I hate that voodoo thing. I'm concerned about two potential problems:

• backwards compatibility breakage for people expecing the H.264 output to default to something; perhaps we should choose a default preset for H.264 which is the closest to the previous configuration;
• quality meaning different things for different codecs (ie different integer ranges / recommended values); granted, users are expected to know the intricacies of the codec, but there's no way they can guess which value should go there unless they read the source of the wrapper or the ffmpeg manpage.

Suggestions or other feedback welcome, if more people are happy with this change, I'll be easily convinced. @Kami?

[tahajahangir]

Removing those options doesn't break anything. Many of them are default options (like -flags +loop , -rc_eq 'blurCplx^(1-qComp)' , ...) and remaining options only affect speed and quality of encoding (not saving format).

[Kami]

I do think that moving towards presets is the right thing to do for the x264 codec.

As far as the backward incompatibility goes - it should be fine as long as we bump the major version and document this change in the changelog

[Kami]

@tahajahangir I noticed your commit c92071c841d20e2ad8f124dcdc764bb3e6197c22 fixed the codec name, but the tests didn't fail in the previous commit which contained a wrong codec name.

We need to add a test case to catch failures like this.

[Kami]

@tahajahangir I've based a pull request on your branch and added a test for vp8 codec there - https://github.com/tahajahangir/python-video-converter/pull/1

[Kami]

Never mind, I see you already merged my branch.

[tahajahangir]

:D

[senko]

I haven't used these options before so I'll defer to your expertise :)

Thanks guys for the patches, there were some conflicts in test.py with the previous pull req so I resolved & merged manually.