[FFmpeg-trac] #3317(undetermined:new): Drawtext+Alphamerge results in incorrect alpha value

FFmpeg trac at avcodec.org
Sat Jan 18 13:36:12 CET 2014


#3317: Drawtext+Alphamerge results in incorrect alpha value
-------------------------------------+-------------------------------------
             Reporter:  jnvsor       |                    Owner:
                 Type:  defect       |                   Status:  new
             Priority:  normal       |                Component:
              Version:  git-master   |  undetermined
             Keywords:               |               Resolution:
             Blocking:               |               Blocked By:
Analyzed by developer:  0            |  Reproduced by developer:  0
-------------------------------------+-------------------------------------

Comment (by jnvsor):

 {{{
 $ ffmpeg -f lavfi -r 30 -t 10 -i "color=c=#FFFFFF" -f lavfi -r 30 -t 10 -i
 "color=c=#000000" -filter_complex
 "[1]drawtext=text="FFmpeg":fontcolor=white:fontsize=150:fontfile=/usr/share/fonts/truetype/dejavu/DejaVuSansMono.ttf[text];[0][text]alphamerge[out]"
 -map "[out]" -vframes 1 -c:v png -pix_fmt rgba alpha.png
 ffmpeg version N-59884-gfd334b9 Copyright (c) 2000-2014 the FFmpeg
 developers
   built on Jan 18 2014 02:17:50 with gcc 4.8 (Debian 4.8.2-12)
   configuration: --arch=amd64 --enable-pthreads --enable-libopencv
 --enable-librtmp --enable-libopenjpeg --enable-libopus --enable-
 libschroedinger --enable-libspeex --enable-libtheora --enable-vaapi
 --enable-runtime-cpudetect --enable-libvorbis --enable-zlib --enable-
 swscale --enable-libcdio --enable-bzlib --enable-libdc1394 --enable-frei0r
 --enable-gnutls --enable-libgsm --enable-libmp3lame --enable-libpulse
 --enable-vdpau --enable-libvpx --enable-gpl --enable-x11grab --enable-
 libx264 --enable-libfreetype
   libavutil      52. 62.100 / 52. 62.100
   libavcodec     55. 48.101 / 55. 48.101
   libavformat    55. 23.103 / 55. 23.103
   libavdevice    55.  5.102 / 55.  5.102
   libavfilter     4.  1.100 /  4.  1.100
   libswscale      2.  5.101 /  2.  5.101
   libswresample   0. 17.104 /  0. 17.104
   libpostproc    52.  3.100 / 52.  3.100
 Input #0, lavfi, from 'color=c=#FFFFFF':
   Duration: N/A, start: 0.000000, bitrate: N/A
     Stream #0:0: Video: rawvideo (I420 / 0x30323449), yuv420p, 320x240
 [SAR 1:1 DAR 4:3], 25 tbr, 25 tbn, 25 tbc
 Input #1, lavfi, from 'color=c=#000000':
   Duration: N/A, start: 0.000000, bitrate: N/A
     Stream #1:0: Video: rawvideo (I420 / 0x30323449), yuv420p, 320x240
 [SAR 1:1 DAR 4:3], 25 tbr, 25 tbn, 25 tbc
 File 'alpha.png' already exists. Overwrite ? [y/N] y
 Output #0, image2, to 'alpha.png':
   Metadata:
     encoder         : Lavf55.23.103
     Stream #0:0: Video: png, rgba, 320x240 [SAR 1:1 DAR 4:3], q=2-31, 200
 kb/s, 90k tbn, 30 tbc (default)
 Stream mapping:
   Stream #0:0 (rawvideo) -> alphamerge:main
   Stream #1:0 (rawvideo) -> drawtext
   alphamerge -> Stream #0:0 (png)
 Press [q] to stop, [?] for help
 frame=    1 fps=0.0 q=0.0 Lsize=N/A time=00:00:00.03 bitrate=N/A
 video:3kB audio:0kB subtitle:0 global headers:0kB muxing overhead
 -100.641774%
 }}}

--
Ticket URL: <https://trac.ffmpeg.org/ticket/3317#comment:2>
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