Deformed particle effect

davide445 Posts: 306 Just Starting Out

Used HF to create a particle effect Shooting Star, a small 1s video with transparent background to be launched as overlay in realtime within a DJ/VJ sw I will use this weekend in an event (not the more advanced use of HF, I know).

Using chroma key I did remove the black background and generated the uncompressed AVI file.

Problem is the falling star appear to be nice inside HF, but deformed inside the video file, next two screenshot

Shooting star inside HF

Shooting star inside the final video

I wanted to play with chroma key settings but none make any difference inside HF preview, so difficult to say what is wrong.


  • AxelWilkinson
    AxelWilkinson Posts: 5,252 Staff

     That's an alpha channel issue. The transparency around the edges is created by the alpha channel, but in order to create the fade, the alpha needs solid color underneath to wok with. You are seeing the color data, without the alpha channel applied. so, you need to change the way the alpha is displayed, I think Premultiplied is what you want, but I might be remembering that wrong. If I am, try the alpha options until you find the one that looks right.

  • davide445
    davide445 Posts: 306 Just Starting Out

    Discovered I can replay the effect in HF setting the color mode in RGB Straight in the preview window.

    This is the MediaInfo of the HF generated AVI (uncompressed, non interlaced, RGBA settings): there is anything I need to change in the export setup? Didn't find any Premultiplied parameter in HF.

    Complete name                            : C:\Miei\Geniya\Scuola\Saggio 2015\Video\Test effetto\Effetto 2.avi
    Format                                   : AVI
    Format/Info                              : Audio Video Interleave
    File size                                : 206 MiB
    Duration                                 : 1s 40ms
    Overall bit rate                         : 1 659 Mbps

    ID                                       : 0
    Format                                   : RGBA
    Codec ID                                 : 0x00000000
    Codec ID/Info                            : Basic Windows bitmap format. 1, 4 and 8 bpp versions are palettised. 16, 24 and 32bpp contain raw RGB samples
    Duration                                 : 1s 40ms
    Bit rate                                 : 1 659 Mbps
    Width                                    : 1 920 pixels
    Height                                   : 1 080 pixels
    Display aspect ratio                     : 16:9
    Frame rate                               : 25.000 fps
    Bit depth                                : 8 bits
    Bits/(Pixel*Frame)                       : 32.000
    Stream size                              : 206 MiB (100%)

  • AxelWilkinson
    AxelWilkinson Posts: 5,252 Staff

    Sorry I was unclear, its not something you need to change in HitFilm, you need to change it in the application you are using to play back the exported file. In the images you attached, that would appear to be Quicktime, IN which case you would open the Properties for the clip, select the video track, then open visual Settings and use the Transparency menu to try the different options.

  • davide445
    davide445 Posts: 306 Just Starting Out

    Mmmm I need in fact to use this small video inside an app named Cross DJ, not sure is possible here to change anything about how alpha channel is used.

    There are anything I can change in HF production process to be sure the file is reproduced correctly?

  • Triem23
    Triem23 Posts: 20,072 Ambassador
    edited June 2015

    Problem here is that the user manual for Cross DJ as available from the manufacturer doesn't talk about it's video capabilities... At all. So, I can't determine what settings Clean DJ might have to deal with alpha channels. You can try exporting your video as a PNG sequence, or add a black plane underneath your star and see if Clean DJ can overlay that in a screen or add mode, but, since the Clean DJ manual has zero information on it's video features, there's nothing I can do to guarantee anything will work for you. 

    It really depends on Cross DJ's software. Hitfilm seems to be functioning correctly. 

  • davide445
    davide445 Posts: 306 Just Starting Out
    edited June 2015

    Nothing to say over HF, simply I didn't find a way to display correctly the video outside HF.

    Using QuickTime, VLC, Windows Media Player I did always obtain the same result, nor did find any way to customize the alpha channel usage. Maybe in QT Pro? I did have the standard version.

    About Cross DJ I will care with it after finding a way to play it correctly on more standard players such above.