How to get alpha channel from RGBA video ?
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How to get alpha channel from RGBA video ?
 
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Hi folks,
I'm trying to get alpha working from a avi video, without success. My video is a set of uncompressed PNG image, 32 bpp. Even if my current code is in Python, the pipeline look like: filesrc location=rgbavideo.avi ! decodebin ! ffmpegcolorspace ! video/x-raw-rgb,red_mask=(int)0xff000000,green_mask=(int)0x00ff0000,blue_mask=(int)0x0000ff00,alpha_mask=(int)0x000000ff,bpp=32,depth=32 ! appsink After getting the buffer from appsink, the alpha channel is still 0xff : >>> print set(self._buffer.data[3::4]) set(['\xff']) The caps detected by decodebin/avidemux is: video/x-raw-rgb, bpp=(int)32, depth=(int)24, endianness=(int)4321, red_mask=(int)65280, green_mask=(int)16711680, blue_mask=(int)-16777216, framerate=(fraction)25/1, width=(int)1080, height=(int)540 With ffmpeg, i'm able to convert the video into png, and the png got the alpha background. FFMpeg show : Input #0, avi, from 'Fleches_3.avi': Duration: 00:00:10.00, start: 0.000000, bitrate: 466965 kb/s Stream #0.0: Video: rawvideo, bgra, 1080x540, 25 tbr, 25 tbn, 25 tbc I've tryied to use ffdemux_avi instead of decodebin, without success. Is anyone have an idea about how to get the alpha channel from the video source ? Regards, Mathieu _______________________________________________ gstreamer-devel mailing list [hidden email] http://lists.freedesktop.org/mailman/listinfo/gstreamer-devel |
Re: How to get alpha channel from RGBA video ?
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What if you do not use ffmpegcolorspace, because capsfilter seems to be correct but caps detected by decodebin/avidemux does not look appropriate since it's missing alpha_mask.
Its just a guess !
On Fri, Mar 18, 2011 at 11:14 PM, Mathieu Virbel <[hidden email]> wrote: Hi folks, -- Regards, Sudarshan Bisht _______________________________________________ gstreamer-devel mailing list [hidden email] http://lists.freedesktop.org/mailman/listinfo/gstreamer-devel |
Re: How to get alpha channel from RGBA video ?
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Ok, yes, alpha is lost when conversion happen. I didn't removed
ffmpegcolorspace, but by removing caps, i'm able to get the alpha channel. But how can i do to have it working with caps ? I don't want to deal with every possible caps available from video, that's why i've wanted to use ffmpegcolorspace. Any tips ? (By the way, what is the difference between bpp and depth ?) 2011/3/18 sudarshan bisht <[hidden email]>: > What if you do not use ffmpegcolorspace, because capsfilter seems to be > correct but caps detected by decodebin/avidemux does not look appropriate > since it's missing alpha_mask. > Its just a guess ! > > > > > On Fri, Mar 18, 2011 at 11:14 PM, Mathieu Virbel <[hidden email]> wrote: >> >> Hi folks, >> >> I'm trying to get alpha working from a avi video, without success. >> My video is a set of uncompressed PNG image, 32 bpp. Even if my >> current code is in Python, the pipeline look like: >> >> filesrc location=rgbavideo.avi ! decodebin ! ffmpegcolorspace ! >> >> video/x-raw-rgb,red_mask=(int)0xff000000,green_mask=(int)0x00ff0000,blue_mask=(int)0x0000ff00,alpha_mask=(int)0x000000ff,bpp=32,depth=32 >> ! appsink >> >> After getting the buffer from appsink, the alpha channel is still 0xff : >> >>> print set(self._buffer.data[3::4]) >> set(['\xff']) >> >> The caps detected by decodebin/avidemux is: >> video/x-raw-rgb, bpp=(int)32, depth=(int)24, endianness=(int)4321, >> red_mask=(int)65280, green_mask=(int)16711680, >> blue_mask=(int)-16777216, framerate=(fraction)25/1, width=(int)1080, >> height=(int)540 >> >> With ffmpeg, i'm able to convert the video into png, and the png got >> the alpha background. FFMpeg show : >> Input #0, avi, from 'Fleches_3.avi': >> Duration: 00:00:10.00, start: 0.000000, bitrate: 466965 kb/s >> Stream #0.0: Video: rawvideo, bgra, 1080x540, 25 tbr, 25 tbn, 25 tbc >> >> I've tryied to use ffdemux_avi instead of decodebin, without success. >> >> Is anyone have an idea about how to get the alpha channel from the >> video source ? >> >> Regards, >> >> Mathieu >> _______________________________________________ >> gstreamer-devel mailing list >> [hidden email] >> http://lists.freedesktop.org/mailman/listinfo/gstreamer-devel > > > > -- > Regards, > > Sudarshan Bisht > > _______________________________________________ > gstreamer-devel mailing list > [hidden email] > http://lists.freedesktop.org/mailman/listinfo/gstreamer-devel > > gstreamer-devel mailing list [hidden email] http://lists.freedesktop.org/mailman/listinfo/gstreamer-devel |
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bpp: "The number of bits allocated per pixel. This is usually 16, 24 or 32." depth: "The number of bits used per pixel by the R/G/B components. This is usually 15, 16 or 24." [ http://gstreamer.freedesktop.org/data/doc/gstreamer/head/pwg/html/section-types-definitions.html ] I posted this just because I was searching this on google and came to this post. |
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