How to get alpha channel from RGBA video ?

[sudarshan bisht]

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 <mat at kivy.org> 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
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>



-- 
Regards,

Sudarshan Bisht
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