Re: [Debconf-video] One proposal about debconf16 videos

On Tue, Jul 26, 2016 at 2:01 AM, Wouter Verhelst <w@uter.be> wrote:

On Thu, Jul 14, 2016 at 12:07:44PM +0200, Wouter Verhelst wrote:
> I don't mind.
>
> However, the easiest way is probably to hack up things so that
> generating a webm file creates a low-res version by default, and then
> setting everything back to "encode" again.

Assuming they are all in the same state (like 12/done)

python enc.py --ready-state=12

That will find the 12's, encode, bump them to 13.

For the future, I should make this easier. veyepar already supports multiple encodes, but currently each needs it's on extension (the use case is: an mp4 for youtube and a webm for download)

What is the typical way of naming the larger/smaller files?

On a similar note, there are 3 more things that could us a bunch of R&D:

1. 2 pass encoding

2. Audio normalization

3. encode script hook.

1. 2 pass -

This should be easy. I have code that should work, but:
# 2 pass causes no video track, so dumping this.
https://github.com/CarlFK/veyepar/blob/master/dj/scripts/enc.py#L453-L460

2. Audio normalization needs looking at. It "works for me" but that may be because my source is good enough and whatever is or isn't happening doesn't matter. result: I haven't put much effort into this in over a year. If someone can dig into this and figure out A) is there a problem and if so, some examples and of course patches!

Here is what currently drives it:

https://github.com/CarlFK/veyepar/blob/master/dj/scripts/template.mlt#L177-L182

Maybe <property name="program">-23.0</property> is wrong?

https://www.mltframework.org/bin/view/MLT/FilterLoudness
"This filter requires two passes." Hmmm.. That looks like a problem.

template.mlt is a functioning ShotCut project file. If you put the input files in place (this will generate them)
https://github.com/CarlFK/veyepar/blob/master/dj/scripts/run_tests.py#L112-L179

There is code that uses template.mlt to create each_talk_slug.mlt which gets passed to this webm encode line:

https://github.com/CarlFK/veyepar/blob/master/dj/scripts/enc.py#L405-L417

3. I should add back in the hook that lets people do their own encode commands without modifying enc.py. I had this years ago, but for some reason commented it out.

script hook:
https://github.com/CarlFK/veyepar/blob/master/dj/scripts/enc.py#L528-L533

But if 1 and 2 get addressed, then no need for it and it can linger on in limbo.

>
> This makes it impossible (or, well, at least "much harder") to fix any
> issues with already-encoded files. I'll therefore postpone this until
> next week or so, so that I'm 100% sure that everything's been dealt
> with.
>
> (also, the encoder was brought down now, so in order to this I'll have
> to recreate its environment on vittoria now. That's not hard, I can do
> it, but it's a bit of work...)

So I've done the above, and generated a low-res version of one talk as a
test, which you can find at
<https://veyepar.debian.org/static/veyepar/debian/debconf16/webm/The_Electronic_Struggle.webm>

The resolution was forced to 360x288, which is half the resolution (in
both directions, so a quarter of) pal-DV at 720x576. The resulting file
is 155M in size, versus 527MB of the full-quality version.

Before I start to do low-res encodes of all the talks, I would welcome
some comments. If there's a possible improvement to be made, now's the
time to speak up.

(VP9 is not a possibility, since the libvpx in stable doesn't support it
yet...)

Regards,

--
< ron> I mean, the main *practical* problem with C++, is there's like a dozen
people in the world who think they really understand all of its rules,
and pretty much all of them are just lying to themselves too.
-- #debian-devel, OFTC, 2016-02-12
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