I am trying to play transparent video using libvlc and libvlcpp.
Video is encoded from transparent PNG files using ffmpeg. Video format is VP9.
Encoding options are: ffmpeg -framerate 30 -f image2 -i %04d.png -c:v libvpx-vp9 -pix_fmt yuva420p transparent.webm
I checked with Chromium-based browser that the video contains an alpha channel.
Here is some code of playback:
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...
media_ = VLC::Media(instance_, "transparent.webm", VLC::Media::FromPath);
mp_.setMedia(media_);
mp_.setVideoFormat("RGBA", 512, 512, 512 * 4); //setting video format to RGBA. Video size is 512×512; pitch is 4 bytes per pixel
mp_.setVideoCallbacks([this](void** pBuffer) -> void* {
//std::cout << "Lock callback" << std::endl;
*pBuffer = buffer_na_;
return NULL;
}, [](void*, void*const*) {
//std::cout << "Unlock callback" << std::endl;
}, [this](void*) {
//std::cout << "Display callback" << std::endl;
std::ofstream buffer_file; //Let's save buffer to file and see what is inside
buffer_file.open("buffer.raw", std::ios::binary | std::ios::out | std::ios::trunc);
buffer_file.write(reinterpret_cast<const char*>(buffer_na_), BUF_SIZE);
buffer_file.close();
});
mp_.play();
...
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00 00 00 FF 00 00 00 FF 00 00 00 FF 00 00 00 FF
...
AF 7A 33 FF AF 7A 33 FF B0 75 33 FF AC 70 2E FF
...
I can even open this file as raw in image editor and it looks correct but with black background instead of transparent.
The question is how can I get data from libvlc with proper Alpha channel.
application output for --verbose=2: https://pastebin.com/RfJEeXYs
