[Kdenlive-devel] External Video rendering

[Dan Dennedy]

On Tue, Dec 11, 2012 at 1:07 PM, Marco Fleckinger
<marco.fleckinger at wikipedia.at> wrote:
> Hello,
>
> On 11/12/12 19:05, Dan Dennedy wrote:
>> On Tue, Dec 11, 2012 at 2:26 AM, Marco Fleckinger
>> <marco.fleckinger at wikipedia.at>  wrote:
>>> Is it possible to export a melt command line from a kdenlive
>>> project, so I could render the project also on another machine
>>> without needing to install a graphical user interface?
>>
>> You can save a render script, but that uses kdenlive_render, which
>> is little more than a wrapper around melt for some special things
>> like making dual pass appear as one job. You do not really need it.
>
> AFAIK not.
>
>> Basically, you can just render the kdenlive project file directly
>> with melt.
>
> Just had a look at such a file and found out that it's indeed looking like
>
> http://www.mltframework.org/bin/view/MLT/MltXml
>
> So <kdenlivedoc /> will be ignored by MLT? As there are just some very

yes

> small thumbnails and other small files in the thumbs directory the
> project-file is referring to, I assume that those are just for the work
> with kdenlive?
>
>> The kdenlive render script will show you the melt avformat parameters
>> for the encoding after kdenlive has done some variable substitutions
>> based on project and render dialog settings.
>
> Ah, you mean the output-profile I would use with melt's consumer? Here I
> have a problem on Debian Wheezy: The profile "OGG/Theora" doesn't work.
> I have to replace several parameters. So instead of
>
> "Theora/Originalversion": acodec=libvorbis aq=3 vcodec=libtheora vq=8
> vb=1024k r=25 aspect=%dar pass=%passes
>
> I needed to use
>
> -acodec vorbis -aq 3 -vcodec libtheora -strict experimental -sameq -vb
> 1024k -r 25 %1.ogv

ok, just edit as-needed. The melt syntax for setting properties is
name=value instead of "-name value".

> when I worked with ffmpeg/avconv. Even compiling ffmpeg from the sources
> didn't work. I didn't know what aspect=%dar means, therefore I didn't
> use it at all in my tests.

The %dar is an example of the Kdenlive variable substitution I mentioned.

> But actually it is not possible to change this profile permanent at all.

You can create a custom render profile based on an existing one.

> At least I could find out how to do so yet. I'm really new to
> video-processing but am locking from a IT-view on this. This helps a lot.
>
> It'd also be really great to help webm and vp8 to get more popular, but
> I couldn't find a default profile for it.

Melt has a preset system too, but also you do not need to be limited to presets.
"melt -query presets" shows you all presets. "melt -query
preset=consumer/avformat/webm" shows the details of a preset.
Use a preset like this: melt ... -consumer avformat:output.file properties=webm
Here, melt knows that you are trying to use a preset with a consumer
named avformat and can formulate the preset path to save you from some
typing.

>> Thus, you can prototype it in kdenlive, make a render script, and
>> then copy the parts of the render script for your own custom
>> melt-only script.
>>
> That was actually the idea: Prototyping in kdenlive using small
> resolution video files. The final resolution will be rendered on a
> server or workstation somewhere in a data-center with better internet
> connection. So many people can work with the same files distributed.
>
>> Please be aware that not everything works in a typical headless
>> configuration. Things like kdenlivetitle and SVG loading require the
>> QtGui module that does not work without an X11 session, but you can
>> use the xvfb virtual X11 server!
>>
> Hm, actually it should run on a server machine, maybe I could arrange
> that somehow. Otherwise I need to generate the videofiles containing the
> results of this routines by using other ways.
>
>>> WikiTV-Team
>>
>> intriguing project name
>>
> Yes, since the preparations for the 10th anniversary of Wikipedia on
> January, 15th 2011 there is also a WikiTV project forming. It should be
> a sister project to Wikipedia as e.g. Wikibooks, Wiktionary, etc. We
> also cooperate with a guy from the ORF (Austria's national broadcaster).

http://www.dorftv.at/ uses MLT, but I do not know how it is related to ORF.

> As we want to support Free Knowledge, we also think that recording Open
> Source talks are relevant for us, as well as some Wikimedia Events. At

http://nextdayvideo.com/ covers conferences such as PyCon and also uses MLT.

> the moment we only operate in the German-spoken area, but would also be
> glad if this was more international.
>
> Less than 6 persons we're looking for people who'd like to join us.
> So if anybody is interested into this project, we would welcome you to
> join us!

I am quite busy as the lead MLT developer, but I can offer you some
MLT-related support as-needed because I think WikiTV is a good
concept.

> There is also a strong reference to Linux and FOSS. The two main people
> visiting different events operating for WikiTV are Linux-Users including
> me :)
>
> Marco