itsoffset has no effect for png stream and overlay/blend filter

[d-fens_]

Summary of the bug:

Hi,

i have two png inputs and want to overlay (same with blend filter but i "downgraded" from blend to overlay during tests)
a background with a overlay for only a certain time.

i expected to see the overlay from 2sec until 4sec, but its there all the time (1-5sec).

How to reproduce:

ffmpeg.exe -r 15 -t 5 -loop 1  -i background.png -r 15 -loop 1 -itsoffset 2 -t 2  -i overlay.png -filter_complex "[1] [0] blend" -y -r 15 test.mp4

ffmpeg version N-74989-gb480f0e Copyright (c) 2000-2015 the FFmpeg developers
  built with gcc 4.9.3 (GCC)
  configuration: --enable-gpl --enable-version3 --disable-w32threads --enable-avisynth --enable-bzlib --enable-fontconfig --enable-frei0r --enable-gnutls --enable-iconv --enable-libass --enable-libbluray --enable-libbs2b --enable-libcaca --enable-libdcadec --enable-libfreetype --enable-libgme --enable-libgsm --enable-libilbc --enable-libmodplug --enable-libmp3lame --enable-libopencore-amrnb --enable-libopencore-amrwb --enable-libopenjpeg --enable-libopus --enable-librtmp --enable-libschroedinger --enable-libsoxr --enable-libspeex --enable-libtheora --enable-libtwolame --enable-libvidstab --enable-libvo-aacenc --enable-libvo-amrwbenc --enable-libvorbis --enable-libvpx --enable-libwavpack --enable-libwebp --enable-libx264 --enable-libx265 --enable-libxavs --enable-libxvid --enable-lzma --enable-decklink --enable-opencl --enable-zlib
  libavutil      55.  0.100 / 55.  0.100
  libavcodec     57.  0.100 / 57.  0.100
  libavformat    57.  0.100 / 57.  0.100
  libavdevice    57.  0.100 / 57.  0.100
  libavfilter     6.  0.100 /  6.  0.100
  libswscale      4.  0.100 /  4.  0.100
  libswresample   2.  0.100 /  2.  0.100
  libpostproc    54.  0.100 / 54.  0.100
Input #0, png_pipe, from 'background.png':
  Duration: N/A, bitrate: N/A
    Stream #0:0: Video: png, rgb24(pc), 640x480 [SAR 3779:3779 DAR 4:3], 25 fps, 25 tbr, 25 tbn, 25 tbc
Input #1, png_pipe, from 'overlay.png':
  Duration: N/A, bitrate: N/A
    Stream #1:0: Video: png, rgba(pc), 640x480 [SAR 2834:2834 DAR 4:3], 25 fps, 25 tbr, 25 tbn, 25 tbc
No pixel format specified, yuv444p for H.264 encoding chosen.
Use -pix_fmt yuv420p for compatibility with outdated media players.
[libx264 @ 0000000002f99e20] using SAR=1/1
[libx264 @ 0000000002f99e20] using cpu capabilities: MMX2 SSE2Fast SSSE3 SSE4.2 AVX
[libx264 @ 0000000002f99e20] profile High 4:4:4 Predictive, level 2.2, 4:4:4 8-bit
[libx264 @ 0000000002f99e20] 264 - core 148 r2597 e86f3a1 - H.264/MPEG-4 AVC codec - Copyleft 2003-2015 - http://www.videolan.org/x264.html - options: cabac=1 ref=3 deblock=1:0:0 analyse=0x3:0x113 me=hex subme=7 psy=1 psy_rd=1.00:0.00 mixed_ref=1 me_range=16 chroma_me=1 trellis=1 8x8dct=1 cqm=0 deadzone=21,11 fast_pskip=1 chroma_qp_offset=4 threads=6 lookahead_threads=1 sliced_threads=0 nr=0 decimate=1 interlaced=0 bluray_compat=0 constrained_intra=0 bframes=3 b_pyramid=2 b_adapt=1 b_bias=0 direct=1 weightb=1 open_gop=0 weightp=2 keyint=250 keyint_min=15 scenecut=40 intra_refresh=0 rc_lookahead=40 rc=crf mbtree=1 crf=23.0 qcomp=0.60 qpmin=0 qpmax=69 qpstep=4 ip_ratio=1.40 aq=1:1.00
Output #0, mp4, to 'test.mp4':
  Metadata:
    encoder         : Lavf57.0.100
    Stream #0:0: Video: h264 (libx264) ([33][0][0][0] / 0x0021), yuv444p, 640x480 [SAR 1:1 DAR 4:3], q=-1--1, 15 fps, 15360 tbn, 15 tbc (default)
    Metadata:
      encoder         : Lavc57.0.100 libx264
Stream mapping:
  Stream #0:0 (png) -> blend:bottom
  Stream #1:0 (png) -> blend:top
  blend -> Stream #0:0 (libx264)
Press [q] to stop, [?] for help
Past duration 0.999992 too large
frame=   32 fps=0.0 q=-1.0 Lsize=       3kB time=00:00:02.00 bitrate=  10.9kbits/s dup=0 drop=43
video:1kB audio:0kB subtitle:0kB other streams:0kB global headers:0kB muxing overhead: 81.441925%
[libx264 @ 0000000002f99e20] frame I:1     Avg QP: 7.00  size:   113
[libx264 @ 0000000002f99e20] frame P:8     Avg QP: 8.12  size:    28
[libx264 @ 0000000002f99e20] frame B:23    Avg QP:11.39  size:    21
[libx264 @ 0000000002f99e20] consecutive B-frames:  3.1%  0.0%  9.4% 87.5%
[libx264 @ 0000000002f99e20] mb I  I16..4:  0.1% 99.9%  0.0%
[libx264 @ 0000000002f99e20] mb P  I16..4:  0.0%  0.0%  0.0%  P16..4:  0.0%  0.0%  0.0%  0.0%  0.0%    skip:100.0%
[libx264 @ 0000000002f99e20] mb B  I16..4:  0.0%  0.0%  0.0%  B16..8:  0.0%  0.0%  0.0%  direct: 0.0%  skip:100.0%
[libx264 @ 0000000002f99e20] 8x8 transform intra:99.9%
[libx264 @ 0000000002f99e20] coded y,u,v intra: 0.0% 0.0% 0.0% inter: 0.0% 0.0% 0.0%
[libx264 @ 0000000002f99e20] i16 v,h,dc,p:  0%  0% 100%  0%
[libx264 @ 0000000002f99e20] i8 v,h,dc,ddl,ddr,vr,hd,vl,hu:  0%  0% 100%  0%  0%  0%  0%  0%  0%
[libx264 @ 0000000002f99e20] Weighted P-Frames: Y:0.0% UV:0.0%
[libx264 @ 0000000002f99e20] kb/s:3.04

Patches should be submitted to the ffmpeg-devel mailing list and not this bug tracker.

[d-fens_]

background example

[d-fens_]

overlay

[Michael Niedermayer]

itsoffset is the wrong tool for this, much more flexible is to conditionally enable the filter as in:

./ffmpeg -r 15 -loop 1  -i background.png -r 15 -loop 1   -i overlay.png -filter_complex "[1] [0] blend=addition:enable='between(t,0,1)'" -y -t 10 test.mp4

of something like this

 -filter_complex "[1] setpts=T+5[t],[0][t] blend=addition"

Feel free to reopen the ticket if you belive that theres a bug