Development

Kdenlive 0.8.2 adds effects and monitoring tools

Video editing in open source is a tumultuous space; projects come and go, and when they stick around they have a tendency to embark on sudden ground-up rewrites and media-framework transplants. But the dirty little secret is that that situation is just as true in the "professional" proprietary market as it is for those of us who stick with free software. Fortunately, while ambitious efforts like Lumiera remain experimental, the formerly low-end nonlinear video editors (NLEs) are closing the feature gap by adding steady, small improvements. Case in point is the KDE-based NLE Kdenlive, which released its most recent update in October 2011. Version 0.8.2 adds new audio/video inspection and monitoring tools, as well as effects that offer real editing functionality — not mere eye-candy. The high end of the market is not as safe as it used to be.

The 0.8.x series introduced a slew of new features — mostly in the "special effects" vein, but some that contribute to better project management and usability, too. The project wiki maintains a near-exhaustive list of build and installation options for users on every platform supported by KDE, including multiple Linux distributions. I opted for the Launchpad personal package archive (PPA) maintained for Ubuntu by Olivier Banus — it was "strongly recommended" over the official repositories, although exactly why is not explained. The primary package dependency to worry about is the low-level video editing framework MLT, which is also used by the GTK+-based OpenShot NLE (and is also provided by most of the project's distribution-specific package repositories).

On the whole, Kdenlive conforms to the same basic user-interface conventions shared by every major NLE. Each editing project you start consists of a set of video, audio, and other media "clips" that you select, and a timeline on which you drop, rearrange, and align those clips. Your experience in the editor is defined by manipulating items on the timeline, and any changes or effects you make to individual clips on the "clip monitor." When you are satisfied with your results, you render the final output into the format you want.

OpenShot, PiTiVi, and Kdenlive all offer largely comparable approaches to this workflow, and have roughly the same level of support for the video input and output formats most people need. Where they differ is in the details: the ability to create special effects, the smoothness of manipulating clips and settings, and support for esoteric non-video content that you might want to generate for use in your production. The canonical example of this is title cards; most NLEs allow you to assemble text and images into title elements directly within the editor (albeit with varying degrees of sophistication), rather than forcing you to create them in an external application. Unlike some of the others, Kdenlive can also generate countdown sequences, clips of solid-color backgrounds, still-image slideshows, and static "noise."

Via MLT, Kdenlive uses a plug-in API called Frei0r for its audio and video effects. The 0.8.2 release includes several hundred effects, ranging from simple audio/video corrections, to image transformations, to decorative effects. Over the years, Kdenlive has also added a series of inspection and monitoring tools that help you get a better handle on the contents of your media files: you can monitor audio waveforms and color scopes as you skip through your video, which makes editing far more precise than relying on pointing your own eyes and ears at the preview window.

What's new

I am not a video professional, but, based on discussions with friends and relatives who are, it is these sorts of effects and monitoring options that make up some of the biggest differences between "consumer" and "professional" NLEs. For example, a lightweight editor will allow you to cut and rearrange clips to your heart's content, but without a way to adjust the colors so that two clips shot in different locations have the same skin tones, the lightweight editor will never be useful for any kind of professional-looking output.

On that front, I am pretty pleased with what Kdenlive currently offers. For video, you have control over hue, contrast, and saturation, complete with adjustment curves (which, as with photographs, allow you to vary the amount of adjustment in different parts of the image) and automatic balancing. The various "scopes" for monitoring a clip include histograms, waveforms, and a vectorscope. For audio, there are standard VU meters, spectrum and spectrogram monitors, plus a dizzying assortment of audio filters.

Among the new special effects are some novelty techniques such as a stop-motion animator and a light-painting tool, but there are others with more practical aims. The first is a perspective image placement tool, which allows you to put a rectangle onto a clip and distort its sides and corners until it appears to match the perspective of other in-frame surfaces. You can then composite a still image (or another video clip) into the properly-aligned rectangle and have it render as if it were physically present in the scene. The second is named rotoscoping, but it essentially just allows you to mask off areas of the screen by drawing Bezier curves right onto the monitor. You can draw such masks on several keyframes, and the effect plug-in will interpolate on the intermediary frames. With a little feathering (i.e. an alpha-transparent border) added to the edges of your mask, you can replace objects or backgrounds. Both of these are effects that proprietary NLEs have offered (on other operating systems) for some time, but their addition to Kdenlive is another sign that the program is growing up.

Also in the "growing up" category are some changes to the user interface and project-management features. The biggest is that the individual components of the UI are all detachable and can be rearranged at will. For starters, this allows you to work around older annoyances like the inability to see the "clip monitor" and "project monitor" at the same time (as noted by editor Jonathan Corbet in 2008). But it also enables you to assemble separate layouts for specific tasks and save them for later reuse, so you can activate all of the audio monitoring options for an "audio editing layout" or set up video monitors for a "color correction layout." There are a lot of monitors in 0.8.2, and fitting them all on-screen at once is not feasible.

The project-management features I found welcome include a "notes" pane which allows you to keep text notes on your work directly within the project (a method that definitely beats maintaining them in a separate file that you periodically misplace), and something called "proxy clips" in the main editors. Proxy clips are CPU-friendly transcoded versions of your original clip which are shown in the effects and preview windows instead of the original, thus saving CPU time and speeding up the responsiveness of the entire UI. When a proxy clip is rendered, Kdenlive uses the original clip, but working on the proxy clip makes life easier at every step up to the final one. In a take-a-moment-to-think-about-it twist, the proxy clips are usually larger in size than the original — it is the highly-compressed HD video formats that consume lots of CPU, after all. Proxy clips decoded to something simpler like vanilla MPEG-2 use more bytes, but don't require overhead for every frame.

The final cut

Kdenlive has evolved considerably since I last took it for a drive (which if I recall correctly, must have been sometime during the 0.6.x series). There are, however, several areas where I still find the editing experience painful. The first is that many of the mission-critical UI widgets are tiny. Although the toolbar buttons for generic items like Open, Save, and Undo get a full 32 pixels each, the timeline's playback point (which you must grab and slide in order to change positions in your movie) is barely 8 pixels high. That is better than the playback point in the clip monitor, however, which is 5 pixels high. Most of the tool buttons on the monitors and timeline are larger than that, but they are still microscopic by GUI standards, which makes them harder to hit and harder to tell apart.

I also found the effects interface inconsistent. It uses bottom-tabs (which is atypical to begin with), but activating an effect is the real issue. A checkbox next to each available filter would be simple and unambiguous, but to activate an effect, you must select it from the "Effect List" tab, then drag it onto the clip on the timeline that you wish to apply it to — after which, it will appear in the "Effect Stack" tab back in the effects window. There is a separate interface for activating and editing transition effects, by means of pulsating icons that appear in the timeline only when you pause the cursor over the right spot. The transient pulsating buttons appear in a few other places when working with the timeline, such as when resizing a clip. That does not make sense to me either; in all of these cases there is nothing to be gained by hiding the button in some circumstances, nor does the animation make the button easier to see or hit.

Ultimately, as is the case with the wildly-varying button sizes, the transient pulsating buttons just contribute to an inconsistent look across the application as a whole. Some of the icons are flat in style, some are 3D and rounded, some have boxes drawn around them and some have circles. All of the new monitors use a black canvas as a background, while the rest of the interface uses the widget library's default color. It may be unfair, but little details like that can turn off potential new users, particularly artsy ones like video editors.

The good news is that Kdenlive is making steady progress in adding the mid-to-high-end features that it will need to eventually make a play for the "pro-sumer" NLE user. That pro-sumer user is not just the Linux fanatic patiently waiting on Lumiera, either — there is a great opportunity in the NLE market right now on every platform. Apple alienated quite a few of its own professional users when it released Final Cut Pro X in June 2011, which many customers considered a downgrade. Certainly lots of them simply jumped ship to Adobe Premiere, but the competition got a thorough examination. From the other direction, EditShare announced in 2010 that it would release a cross-platform version of its flagship Lightworks NLE as open source, but it has subsequently pushed back the release date to "to be announced." Meanwhile, the existing open source projects — including Kdenlive — keep on plugging away, release by release, feature by feature.

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