success on the (video) alpha channel front

[blackdot]

i had success exporting an image sequence with a premultiplied alpha channel from both blender and adobe premiere, retaining the alpha information in both cases. magic is able to read them perfectly.

i thought i'd write this down, incase it may be useful for somebody else.

Exporting from blender (2.71), i had success using the 'png' video codec (apparently this is also a video codec) which is available once avi, quicktime or matroska is chosen as container (under rendersettings>encoding), which one of those three container is selected doesnt seem to matter (you'll get an avi, mov or mkv file). once png is selected, 'rgba' becomes available in the menu above (rendersettings>output), which also needs to be selected. the video can then be exported.

From a premiere standpoint, i had only success with an avi container and 'none' codec (in the export settings>video). Then a 32-bit option becomes available, which seems to include the alpha channel. The video can be exported now. The disadvantage here: Those uncompressed files are quite big (40mb for ~1s of film). On the other hand this might come in handy with magic, as it wont have to decompress anything anymore and if your disk is fast enough (if i understood Eric correctly).

If you create your content in blender from the beginning, rendering as png image sequence or video sequence as described above, is not the only thing important. you'll also need to tick "transparent" under rendersettings>Film to make the "world background transparent with premultiplied alpha".

That's all, I hope this will be helpful.

[Magic]

Thanks! That is very helpful.

Uncompressed files will probably be too big and slow for most people. But the png option seems pretty good; I wish more applications supported it.

[blackdot]

have an update here, as i was dealing and experimenting with video-alpha channel able codecs again. Again by exporting to different formats and codecs from within blender. i (re)discovered two other types of codecs next to the png-video codec.

there is also eg. matroska (container) and the HuffYUV codec

also Quicktime (container) and the "QT rlr / QT Animation" codec.

All of them produce a video with an alpha channel.

I had a 3 seconds clip (that includes a very detailed colored object in motion) and the file sizes turned out as follows:

HuffYUV: 93mb
PNG: 21mb
QT rle/.. : 26mb

in terms of fps load in magic, i turned off double buffering to get a maxed out framerate. with an empty magic and two monitors hooked up my gpu, of which one shows the magic full screen window, i get about 3200fps.

huffyuv: ~2650fps
PNG: ~2000fps
QTthingy: ~2900fps

differences in vram load seem insignificant. interestingly, the PNG gets the most penalty fps wise. i guess i'll stick to the QT-thingy codec for now, as long as it's also capable of nicely looping a video. will test that soon.

\\edit: ok, seems QT loops pretty smooth, like PNG. HuffYUV jumps at the end of the clip.

tl;dr
QT rle / Animation > PNG-videocodec > HuffYUV. use the quicktime container for the quicktime codec.