One disadvantage Kdenlive has, after OpenShot

On built-up Linux computers, we have two important nonlinear video editing applications available from the package manager: “” and ““. As the naming would suggest, is centered on the K-Desktop-Manager, while is not. Both use the video processing library as their back-end.

(Edit: I goofed, first when I attempted to transcode the video using , and then again, when I wrote this posting about it.

What I had expected to find in the Project Settings of , was that the two “NTSC” formats be grouped together somehow, similarly to they are with , starting with “NTSC”. Instead, has a long drop-down list, which is alphabetized by the software itself – not the programmers.

It has the setting simply named “NTSC”, which refers to the older, 4:3 version. But then, when the user wants to find the 16:9 version, he must scroll way up along the drop-down list, until he gets past the “HD” entries, all the way to the entry “DV/DVD Widescreen NTSC”. And then that setting will perform as expected.

therefore does not have this weakness, but my mistaken choice of output formats, was in fact the true reason for the malformed video file that resulted. )

There is a specific feature in , which does not work properly. To understand what is expected of this feature, the reader must first of all understand something about the background of analog video.

Back in those days, the NTSC, PAL or SECAM signal format assumed a 4:3 aspect ratio, which was later translated into a digital equivalent, which in turn simplified the resemblance to analog, by assuming a pixel aspect of 1:1. This first resulted in the VGA format. In other words, in order for a rectangle of square pixels to have a ratio of 4:3, it would have needed to be a 640×480 resolution image. Because of the way analog signals were processed in practice however, an analog video signal could never really distinguish anywhere near 640 lines of horizontal resolution. 483 vertical scan-lines were smeared horizontally by the filters, to result in maximally 480 horizontal points in the case of NTSC, and that would have been, assuming a comb-filter was used, which was also not available in the early days of TV. In reality, when the signal-format was adapted to DVDs, a strict NTSC format was defined, that consisted of 486 vertical scan-lines, but which had 720 points horizontally, a pixel-aspect of 8:9, and the frame-rate was kept consistent with the 29.97 Hz the analog signal had. This latter deal may in fact be important in video editing, because if an incorrect frame-rate is combined with correct sound-compression from today, an eventual loss of synchronization may result, after longer intervals of play.

At some point in time, picture-aspects of 16:9 started to become popular with DVDs, and their format was adapted to this, by making the pixel-aspect 32:27, and maintaining 720 horizontal points. The question follows, how this change in aspect-ratios was sent along to an analog TV, and the answer would lie in the fact that analog TVs had several modes with which to display a 4:3 signal on their 16:9 physical screens, one of which was to letter-box, another of which was to oversize, and another was just ‘to stretch to make it fit’. Viewers would simply observe that this last option sometimes produced distorted results and sometimes not.

I.e., Nothing was done to communicate the meta-data; the picture was simply stretched to 16:9 on-demand, by the viewer settings.

The sad fact about , is that somehow, it does not work with this notion correctly. As many video-editing applications may do, has a set of presets which the project is formatted to, as possible output-formats, and one of them is the Strict NTSC. This setting assigns some number of pixels, but still assumes an aspect ratio of 4:3, even when the user wants 16:9.

OTOH, has a clear setting for NTSC, but in 16:9 instead of in 4:3. I have not tried them with PAL.

This failure of to process its meta-data correctly, has already slowed down one of my projects recently. I had a number of arbitrarily-formatted MP4 videos, and felt at first that the easiest way to transcode those into NTSC – 16:9, would have been just to open each in , but to set the output format to Strict NTSC. And the results were MPEG-2 -compressed streams which other, external player-applications could not play back.

Under the circumstances this was not a major setback, because I found an appropriate set of ‘‘ command-line-recipes, which transcoded everything as I needed it. But a full-featured video-editing application needs to be able to make this format one of its targets.

Continue reading One disadvantage Kdenlive has, after OpenShot

An Alternative to OpenShot under Linux

In the past, I used to be a fan of the non-linear video editor named “OpenShot”. It is the kind of editor which allows for multiple source clips to be added to multiple, parallel timelines, and for transitions and effects to be added, to put those together into a longer video presentation. One could say that OpenShot was a software-end to the process of compositing. In the past, I had even custom-compiled version 1.1 of OpenShot on the Linux computer I name ‘Walnut’, and gotten that into a state in which it could be used. This means that I did not write the source code in any way, but that I did overlook a lengthy process, by which this source code could be translated into an executable program, on a platform which would not ordinarily have supported it. However, v1.1 still lacked many of the features which later versions claim to have, and that eventually become necessary. V1.1 did not have the Blue-Screen or Green-Screen, Chroma-Key effect.

These days, OpenShot v1.4.3 is directly available through the (Linux) package manager under Debian / Jessie. But I don’t use it, mainly because I cannot. I seem to have discovered that there are major stability issues with recent versions of this video editor. On my Linux box named ‘Phoenix’, this video editor actually caused my desktop to freeze – not once but three times. Almost all my other, package-installed software, is comparatively well-behaved, and I have no other reason to think, that my graphics chipset is in any way faulty.

Under Linux, even a defective application run in user space, should not be able to get the desktop to freeze.

There is also a Windows version, v2.0.6, which I next tried to install on the Windows 7 computer named ‘Mithral’. I did not like the fact to begin with, that this is the type of install which asks the user to reboot Windows for the changes to take effect. But then I also found that the Windows version would constantly crash. Next, having OpenShot v2.0.6 installed under Windows, actually prevented a ‘GPG4Win’ application named “Kleopatra” from working on ‘Mithral’. This last detail worries me.

Yet, after I uninstalled OpenShot from the Windows computer and rebooted again, Kleopatra was working again.

And so the bottom line for me is, that this once-great video editor is now too unstable to be used.

On the Debian / Jessie, Linux computer named ‘Phoenix’, I can use “Kdenlive” instead, which does more or less what OpenShot was supposed to do, and which does these things without crashing. Kdenlive also offers the user to place video clips he supplies into multiple timelines, and to apply transitions and effects, and does include the “Blue Screen” (alpha / translucency) effect.

But under Windows, I can still only see paid-for solutions to this need.

Dirk