[Kdenlive-devel] Usability test (by me!)

[Jason Wood]

On Friday 22 Aug 2003 1:04 pm, Rolf Dubitzky wrote:
> On Wednesday 20 August 2003 11:50 pm, Jason Wood wrote:
> > 1. The first step I had was therefore converting them to rawdv - not too
> > hard but not done via Kdenlive, I used Kino to do this. I missed the fact
> > that there appears to be no way to batch-convert files to a new format,
> > but then, that's not really what kino is there for.
>
> ;-) but that what piave is there for. You could probably do this at the
> command line with piave_CVS-00-03-devel. Even better, you could just use
> the .avi files ;-)

Very true :-)

> > - The first thing was sound sync with the video. Rolf has already
> > mentioned this is improved in the 0.3.0 branch of piave by using arts
> > directly, but it is very annoying trying to watch back your movie and
> > "mentally shift" the sound back to where it's supposed to be.
>
> Yes, this is a problem. mplayer and xine both assume some audio latency
> based on experience and allow to in/decrease AV-delay while watching. I
> will probably have to do something similar. Maybe we can privide a small
> clip with a flap, so you adjust some kind of latency parameter for you
> system. Not using artdsp, however, does already help a lot.
>
> > - I had the same shot filmed at two different camera angles. Syncing up
> > the video/sound was relatively straight forward. But damn, the sound
> > quality between the cameras was so different it was way too noticable!
> > The real solution to this is to have video seperate to sound, so that one
> > camera's sound (or an mp3/off/wav file) can be used throughout and the
> > other video(s) simply displayed over the top.
>
> ;-) almost done ;-)   the piave version on my laptop can read wav/ogg/mp3
> and ... well, and nothing more, not play anything or re-encode, but I am
> currently working on it. I think blending audiotracks together is not too
> far away, too.

Ok, that's good, so the only thing missing is the support from Kdenlive. That 
is kind-of in place - there are audio tracks that are currently not used, but 
could be brought back, and then the VEML will need to be updated to handle 
video and audio seperately.

> > - Because the cameras both had mono sound, the dv files were the same -
> > functionality to take sound from either the left or right channel and use
> > it for both channels is a must.
>
> ok. trivial, that can be done. the main problem is probably to invent VEML
> to do it.

I suppose it depends on if it is done as a special case, or as a piave effect 
- in which case it is rather that we need the effect framework in place.

> > - On the back of this, I missed not being able to fade sound in/out :-)
>
> well, up to now, there is not a single audio-effect, only some video
> effects in various states of bitrot. But since I finished my thesis a few
> days ago, and started working on exactly this, I think you can have a
> audio-volume-filter pretty soon. BTW, taking audio from one DV file and put
> it into the other does workalready, there is just no VEML for it.
>
> > - video crossfade - for the clips I was editing together, a simple
> > crossfade effect would have been quite adequate to make the end result
> > much better.
>
> piave can do this. the effect suffers some minor bitrot. and, more
> important, we have no really working VEML definition for effects (and no
> GUI ;-)

So we need effects , basically :-)

> > Things that would have been nice :
> >
> > - Having sound images in Kdenlive so that you can visually see the
> > 'beats' in music, or when somebody starts speaking.

This is one thing that I have very little idea as to how to implement. It 
comes down to ownership - whose job is it to generate the sound waveforms? 
It's a slightly odd task to as Piave to do, however for Kdenlive to do it, it 
needs to have the raw audio which only piave has.

> > - If piave crashes, it does take a minute or so before a connecion can be
> > re-established. Some sort of rotation of port numbers so that a new port
> > is tried each time should help remove this problem completely. This does
> > not mean that we should stop bug-fixing though!!! :-)
>
> this just treats the symptom. I just have to look into a network
> programming howto. There are two things to it:
> 1)  Fix the tcp/ip communication and make the socket be freed in case of a
>     crash
> 2)  detect when piave and kdenlive are running on the same host and replace
>     the tcp socket by a unix domain socket. This will improve speed and
>     especielly reduce latency a lot. This is what XWindows does and can be
>     done by changing a hand full of source code lines.

Ok, that does sound like a good idea.

> > - Being able to select in/outpoints works like a dream!
> > - The piave in the workspace monitor crashed once or twice , I did not
> > lose my project! (There seems to be an issue with long timelines, piave
> > inserts <message></message> tags which do not always make the end
> > scenelist valid XML. I hope to look into this, since I want to
> > rationalize the XML code in Kdenlive at least anyway.)
> > - The rendering was nice and fast, and came out exactly as it played
> > during the edit.
>
> That makes me happy ;-) However, it is not too surpizing that it was fast,
> since you probably didn't do any real rendering at all. And since piave is
> designed by the principle of delayed action, which means that a video or
> audio frame in the render tree is only decoded as soon as it is _really_
> necessary to alter the video/audio information. If you don't do anything,
> just cut/rearange, the video/audio is not decoded at all. That also means,
> that you don't have _any_ kind of quality loss. you can rearange your clips
> as often as you like. (at least in DV format)

Oh, ok, we need to do something so we can test the rendering speed of piave 
then :-)

> > Right, I'll switch back to the developers hat. Please feel free to
> > comment!
>
> I think I will merge the avi and sound stuff from the devel branch to the
> main branch as soon as seperate audio tracks are working. We should try and
> get another synchronized kdenlive/piave release, 0.2.4/5 or something. mpeg
> support is not something that will work in the next weeks. This will
> probably help people testing the stuff. I would also like to supply some
> packages. I guess we probably have enough people here to  make Mandrake,
> RedHat, and debian packages. Since I will be moving to another town to
> start a new job at Sep. 1st, I guess maybe we can aim at the first or
> second week of Sept. for this, what do you think?

I'll post a seperate 'plan of action message' in a minute to give us something 
to discuss :-)

Cheers,
Jason

-- 
Jason Wood
Homepage : www.uchian.pwp.blueyonder.co.uk