[FFmpeg-trac] #3302(avfilter:new): Cannot draw opaque text on transparent frame
FFmpeg
trac at avcodec.org
Tue Jan 14 05:00:30 CET 2014
#3302: Cannot draw opaque text on transparent frame
----------------------------------+--------------------------------------
Reporter: Krieger | Type: defect
Status: new | Priority: normal
Component: avfilter | Version: git-master
Keywords: | Blocked By:
Blocking: | Reproduced by developer: 0
Analyzed by developer: 0 |
----------------------------------+--------------------------------------
Summary of the bug:
Below testcase may seem somewhat artifical and impractical.
But actually with ffmpeg we can save transparent video (e.g. {{{ -vcodec
png -pix_fmt rgba out.mov}}} )
So let's say we want to render a video with opaque text over transparent
background, for later overlaying. It ends out with the fact that we
cannot: with background alpha = 0 and text alpha = 1, nothing is seen on
image. We must increase background alpha, which not acceptable for desired
result.
How to reproduce:
{{{
ffmpeg -f lavfi -i
"testsrc[testsrc];color=color=white at 0.0,drawtext=text=TEST:fontsize=50:fontfile=/usr/share/fonts/corefonts/verdana.ttf:fontcolor=red at 1.0[text];[testsrc][text]overlay"
/tmp/tmp.ts
ffmpeg version N-59815-gb79bccb Copyright (c) 2000-2014 the FFmpeg
developers
built on Jan 14 2014 03:29:50 with gcc 4.6.3 (Gentoo 4.6.3 p1.13,
pie-0.5.2)
configuration: --enable-gpl --enable-libx264 --enable-encoder=libx264
--disable-stripping --enable-debug --extra-cflags='-O0 -g -ggdb' --enable-
libopus --enable-libvpx --enable-x11grab --enable-libfreetype --enable-
filter=drawtext --enable-libzvbi
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
'testsrc[testsrc];color=color=white at 0.0,drawtext=text=TEST:fontsize=50:fontfile=/usr/share/fonts/corefonts/verdana.ttf:fontcolor=red at 1.0[text];[testsrc][text]overlay':
Duration: N/A, start: 0.000000, bitrate: N/A
Stream #0:0: Video: rawvideo (Y4[11][8] / 0x80B3459), yuva420p,
320x240 [SAR 1:1 DAR 4:3], 25 tbr, 25 tbn, 25 tbc
File '/tmp/tmp.ts' already exists. Overwrite ? [y/N] y
Output #0, mpegts, to '/tmp/tmp.ts':
Metadata:
encoder : Lavf55.23.103
Stream #0:0: Video: mpeg2video, yuv420p, 320x240 [SAR 1:1 DAR 4:3],
q=2-31, 200 kb/s, 90k tbn, 25 tbc
Stream mapping:
Stream #0:0 -> #0:0 (rawvideo -> mpeg2video)
Press [q] to stop, [?] for help
frame= 2313 fps=750 q=9.4 Lsize= 3047kB time=00:01:32.48 bitrate=
269.9kbits/s
video:2538kB audio:0kB subtitle:0 global headers:0kB muxing overhead
20.054615%
Received signal 2: terminating.
}}}
--
Ticket URL: <https://trac.ffmpeg.org/ticket/3302>
FFmpeg <http://ffmpeg.org>
FFmpeg issue tracker
More information about the FFmpeg-trac
mailing list