2013-10-06

Effectively Working with 2.7K (Protune) Footage in Kdenlive

Working with high-bit rate footage that was shot with a GoPro HD Hero 3 Black Edition easily eats up all your available computational resources in post production. Especially for footage shot in the 2700×1520 dimension and with Protune switched on your video editor needs to process around 45MBits per second for real-time playback, applying all the required effects such as color grading, sharpening, et cetera at the same time. However, unless you happen to possess a really highest-end system, these image bit rates are still too much for effectively working in your video editor software. You will quickly grow tired of heavy delays when editing. Luckily, Kdenlive has something to speed up your work again...

Proxy Clips to the Rescue


In Kdenlive, you can seamlessly work with so-called «proxy clips»: these are reduced variants of your original source clips. As they are reduced in size and bit rate they can be processed much faster than your raw source clips. Most of the time, working with proxy clips is totally transparent, except for the increased speed.

Kdenlive already comes with several profiles for working with proxy clips of different dimensions and bit rates. However, I personally found the predefined profiles to be unsatisfactory for my purposes. In the following I will thus show you how easy you can create your own proxy clip profile which you can then tweak to your will.

Note: Kdenlive's proxy clips are only used for display and playback while working on your project. When finally rendering your project, Kdenlive uses the original clips instead in order to avoid loss of quality.

Create a New Encoding Profile for Proxy-Clips


The first thing we need to do is to create a so-called encoding profile in Kdenlive. We will configure this profile to create proxy clips automatically in significantly reduced size and also quality, so it even gives a decent playback experience on my rusty i5 quadcore system. Depending on your video editing system, you may want to experiment with other settings for optimal tuning.

I did not optimize the encoding profile I'm showing here; there surely is room for improvement. My focus is on a simple profile that doesn't eat up too much disk space, yet still can be handled fast and is sufficient for grading, sharpening, and so on.

1. Configure Kdenlive: Project Defaults


Menu Setting,
Configure Kdenlive, topic Project Defaults.
In order to create the new proxy clip encoding profile go to the Settings menu, then Configure Kdenlive. You should see now the Configure dialog. In the topic list to the left of the dialog, select Project Defaults.

We're only interested in the bottom right part where we can find a tick box labelled Proxy Clips. Make sure to tick it.

Also tick the next tick box in order to create proxy clips for video clips that are larger than 1000 pixels.

In addition, we now need to create a suitable render profile. So, please click on the wrench symbol next to the row labelled with Encoding profile.

2. Manage (Proxy Clip) Encoding Profiles


Managing encoding profiles.
This will open a new dialog for managing encoding profiles. Make sure that it says to manage proxy clips. If you don't see this, then select them from the drop down list.

Depending on your Kdenlive installation you may see some encoding profiles or even none at all. It doesn't matter as we now create a new one. Click on the plus button in the bottom left of the dialog.

3. Set Up the Encoding Profile


Create your own new encoding profile.
Again, a new dialog opens. Make sure to give your new encoding profile a name. Otherwise you will loose your settings. Not exactly good usability...

As the parameters just copy the following:
-f mpegts -acodec libmp3lame -ac 2 -ab 128k -ar 48000 -vcodec mpeg2video -g 5 -deinterlace -s 1080x720 -vb 4000k
This simple encoding profile creates MP2 video proxy clips with MP3 audio in reduced dimensions 1080×720 and at most 4MBit/s video bitrate. When you are applying video effects heavily, you may want to reduce the video size even further.

Click on the Save button in order to finally create the new encoding profile. Then close the managing dialog also.

We're almost done: select the encoding profile HQ 720p MPEG you just created a minute ago the project default settings. Click on Ok to save your configuration.

That's it.

Create New Project


Start new project for
GoPro Protune footage...
We will now test drive our new encoding profile to see the results. Create a new Kdenlive project; I'm typically sticking to 1080p final video dimension with 25 frames per second. Not really action video to be honest...

However, if you ever happened to come across badly tempered pike-perches or some larger catfish you will probably agree that this can also be action ... of a different kind.

Make sure that in your project settings you have ticked the box to create proxy clips. Also tick the box to create proxy clips for video clips larger than 1000 pixels.

Finally, make sure that your newly created proxy clip encoding profile HQ 720 MPEG is selected. If all this is okay, then accept with Ok.

Now add one or more video clips to your project that you shot with a GoPro HD Hero 3. Most preferrable, shoot in the 2.7K dimension and with Protune on. Kdenlive will bitch, just ignore it. Of course, we know that the footage has a different size from the final output. That's on purpose, as we don't intend to render in the dimension of 2700×1500... So, click Ok.

You should now see small progress bars appearing inside the preview images of your video clips. Creating the 1080p proxy clips from the 2.7K footage will take some time. When a proxy clip has been created successfully, Kdenlive will show a black P on yellow background inside the clip preview image in the project clip list.

When you now play such a clip for which a proxy clip has been created you should notice that it requires much less CPU resources and should be stutter-free. You may notice the reduced quality, if you look carefully. Normally, this shouldn't matter at all, unless you are tweaking the parameters of the sharpening effect. Anyway, you should always render to final quality from time to time in order to check your effect filter settings.

Working With Proxy Clips


Finally, you can easily switch off and on proxy clips for each individual video clip. You will need this in some special situations, for instance, when you want to save a particular video frame for further processing. Another example is twiddling the sharpening effect settings.

Just right click on a video clip in the project clip list. The context menü contains the item Proxy clip for switching on or off the proxy clip.

Congratulations, you've just mastered your first steps in effectively working with Protune footage in Kdenlive!

Further Posts: Grading


There are further interesting things to know about when working with GoPro HD Hero footage in Kdenlive, so feel free to read on in these blog posts:


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