[FFmpeg-soc] why it is not possible to overlay with negative 'y' position?

[Oleksandr Bondar]

Hello,

Why it is not possible to use overlay filter with negative y
coordinates? It works when x is negative but not y.
How this can be fixed?

stack trace:
ffmpeg -i in3.flv -vfilters
"[in]setpts=PTS-STARTPTS,[T1]overlay=-20+13*atan(N/40):-20+14*atan(N)[out];movie=0:flv:in2.flv,scale=487:365,setpts=PTS-STARTPTS[T1]"
 out.avi
FFmpeg version SVN-r20390, Copyright (c) 2000-2009 Fabrice Bellard, et al.
 built on Nov  3 2009 21:51:11 with gcc 4.4.1
 configuration: --enable-libmp3lame --enable-libvorbis --disable-mmx
--enable-shared --enable-nonfree --enable-libtheora
--enable-avfilter-lavf --enable-avfilter
 libavutil     50. 3. 0 / 50. 3. 0
 libavcodec    52.37. 1 / 52.37. 1
 libavformat   52.39. 2 / 52.39. 2
 libavdevice   52. 2. 0 / 52. 2. 0
 libavfilter    1. 6. 0 /  1. 6. 0
 libswscale     0. 7. 1 /  0. 7. 1

Seems stream 0 codec frame rate differs from container frame rate:
60.00 (60/1) -> 29.97 (30000/1001)
Input #0, flv, from 'in3.flv':
 Duration: 00:00:30.80, start: 0.000000, bitrate: 414 kb/s
   Stream #0.0: Video: h264, yuv420p, 480x360 [PAR 1:1 DAR 4:3], 414
kb/s, 29.97 tbr, 1k tbn, 60 tbc
   Stream #0.1: Audio: aac, 44100 Hz, stereo, s16
 Metadata
   duration        : 31
   starttime       : 0
   totalduration   : 31
   width           : 480
   height          : 360
   videodatarate   : 404
   audiodatarate   : 107
   totaldatarate   : 513
   framerate       : 30
   bytelength      : 2009597
   canseekontime   : true
   sourcedata      : B4A7D0AC6
   purl            :
   pmsg            :
Output #0, avi, to 'out.avi':
   Stream #0.0: Video: mpeg4, yuv420p, 480x360 [PAR 1:1 DAR 4:3],
q=2-31, 200 kb/s, 29.97 tbn, 29.97 tbc
   Stream #0.1: Audio: mp2, 44100 Hz, stereo, s16, 64 kb/s
Stream mapping:
 Stream #0.0 -> #0.0
 Stream #0.1 -> #0.1
Press [q] to stop encoding
*** glibc detected *** ffmpeg: munmap_chunk(): invalid pointer:
0x00000000009e0190 ***
======= Backtrace: =========
/lib/libc.so.6[0x7fefb158ddd6]
/usr/local/lib/libavfilter.so.1(avfilter_default_free_video_buffer+0xc)[0x7fefb2f1bb3c]
/usr/local/lib/libavfilter.so.1(avfilter_unref_pic+0x1a)[0x7fefb2f1a91a]
ffmpeg[0x40893d]
ffmpeg[0x40d094]
ffmpeg[0x40ddb1]
/lib/libc.so.6(__libc_start_main+0xfd)[0x7fefb1536abd]
ffmpeg[0x404859]
======= Memory map: ========
00400000-00415000 r-xp 00000000 08:01 67199
 /usr/local/bin/ffmpeg
00614000-00616000 r--p 00014000 08:01 67199
 /usr/local/bin/ffmpeg
00616000-00617000 rw-p 00016000 08:01 67199
 /usr/local/bin/ffmpeg
00617000-0061c000 rw-p 00000000 00:00 0
006d2000-00a93000 rw-p 00000000 00:00 0                                  [heap]
7fefb03df000-7fefb03f5000 r-xp 00000000 08:01 839
....