FAQ, Known Problems and Workarounds

Some workarounds for issues and a few known problems that have not yet been fixed, are described here. More workarounds can be found here.

Workaround for access to modifiable text files when using AppImage.

This includes such files as FFmpeg video or audio files, fonts that you want to add for usage in the Title plugin, icons that you wish to modify, standalone programs, and any other text file for customization. To get access, first extract the files from the AppImage, find the files to add, edit, or modify, and then run the extracted binary following the steps shown here. For more detailed information on working with AppImages, see B.10.1.

Workaround for the alpha channel not working as intended when using an EDL inserted as a reference or when an EDL is nested.

Using the Projector on the EDL within a Master Project follow these next steps. This solves the alpha channel not working as expected and the Master Project now looks correct.

Workaround for using a transition, like Dissolve, between 2 edits with the plugin Motion51.

In this case, the Motion51 plugin and the Dissolve transition are not seen during the transition phase and is stopped at the cut point between 2 edits. The left edit's plugin should be in effect until the end of that clip and should include the dissolve. Instead, there is a jump inside the dissolve, as if the plugin does not exist. There are 2 possible workarounds. For example, extend the Motion51 plugin to cover both clips rather than having a separate plugin for each clip. Or another workaround is to use two tracks and have the plugin cover the cut point and use a Fade auto instead of the Dissolve transition.

The Fade auto in certain circumstances produces an unwanted black flash.

When you insert an effect on an empty track the fade fades as if it were on a black background; it interprets the alpha as black where there is transparency, which is what produces the fade. So the problem in the case of text is that the letters appear as a black flash briefly in the first few frames, then goes back to transparent, then the fade starts normally with the white color. To avoid the unwanted effect produced by the fade over black (because there is no content) leave the fade in/out of the effect at 0 and use the fade line to perform the intended results to avoid the problem with the alpha channel. The same problem occurs when using transparent PNG images with fade video transitions and can be resolved in the same manner. However this workaround can be quite tedious and complicated if you want to fade many snippets of text and transparent PNGs on the same track, with always the same video transition filter set to the same duration.

Just a side note here. Fade in/out in the Title plugin works fine if there is a clip/image above the plugin in the same track without an alpha channel but not if there is no clip/image. And the Transition effect works fine when there is a transition between two clips/images without an alpha channel.

Detailed explanation:1

If we apply the Dissolve transition, what should actually happen mathematically? For channels r, g, b the contribution of the 1-st clip should gradually fall from 100% to 0%, and the contribution of the 2-nd rise from 0% to 100%. If we have no alpha channel, this is quite simple. If we have, perhaps the alpha channel should gradually change from the a-value of the 1-st clip α1 to the α-value of the second ( α2). For example, if the 1-st clip is a PNG image with opaque letter over some considered pixel, and the 2-nd clip is a PNG with a completely transparent background, the α-value should gradually fall from 100% to 0% for that pixel.

We can easily look with our eyes which color has an area with complete opacity ( α = 100%). r=g=b=100% is white, 0% is black, 100/0/0% is red, etc. But what color is hindered under complete transparency? When α = 0%, we will always see black. But actually it could be red, or even bright white, but completely masked out by 0% alpha.

Now let's apply our mathematics with channels. Somewhere in the middle of the Dissolve transition we should get about 50% of alpha, if α1 = 100% and α2 = 0%. But what for rgb?

If rgb1 was 100/100/100% (white), and rgb2 was also 100/100/100% (fully transparent white), then we will have rgb=100/100/100%, α = 50%. This will look as medium grey, 50% of white.

If rgb1 was 100/100/100% (white), but rgb2 was 0/0/0% (fully transparent black), then we will have rgb=50/50/50%, α = 50%. This will look as rather dark grey, only 25% of white.

If rgb1 was 100/100/100% (white), but rgb2 was 100/0/0% (fully transparent red, but visually still looking as black on black background), then we will have rgb=100/50/50%, α = 50%. This will look not as grey anymore, but a bit reddish.

So, the 0% alpha channel can hinder any actual color of the masked picture, which can become visible if alpha rises above 0% due to applying some transition of effect.

Do not change Color Model Format in session just before loading backup.

Under certain circumstance if you change the Color Model in Settings->Format, quit the session, and then "Load backup" when you start again, it will crash. Workaround is to avoid this scenario.

Audio tracks align with no video track, and in working with Mixers.

The use of Open Mixers always requires the existence of a video track. See But, I want to use only the first set of audio tracks... We cannot act on audio tracks only, for example to align them. A workaround to get the audio tracks aligned would be:

  1. You create/open the Mixer Viewer with Open Mixers in Resources window for the Videos with Audio. It will create, in the timeline, one Video track and two Audio tracks for each Media (Video/Audio), and its Mixer Viewer.
  2. Add a new Video track (Shift+T shortcut) and two Audio tracks (t shortcut) for your audio (Left+Right channels?) without video: you are adding an empty Video track because Align Mixers feature needed a video track.
  3. Move the Video track down until it is on the top of the two Audio tracks.
  4. Insert your Audio into the two Audio tracks in the usual way.
  5. Open/Create a Mixer Viewer from Menu Window Mixer... Mixer Viewer (Shift+M).
  6. Assign that Mixer Viewer (a white frame is shown when selected) to the one Video tracks (empty) and two Audio tracks, of the #2 point, pressing the arrow icons (Mixer) you find on the Patchbay on the left of the Main window. When assigned, you must to see the 3 arrow (for 1video + 2Audio) are pointing up.
  7. Now, you can use Align Mixers feature as usual. See Audio/Video sync using Waveforms/Timecodes
  8. If you use the Viewer to make a clip and then try to "Open EDL" on that clip in the Resources Clip folder window, it will crash. Always use Open EDL with media on the timeline Main Program window.



Footnotes

... explanation:1
Thanks to sge
The CINELERRA-GG Community, 2021
https://www.cinelerra-gg.org