[FFmpeg-trac] #3021(avformat:new): "Invalid block label" error while converting GIF

[FFmpeg]

#3021: "Invalid block label" error while converting GIF
----------------------------------+----------------------------------
             Reporter:  hackPNZ   |                     Type:  defect
               Status:  new       |                 Priority:  normal
            Component:  avformat  |                  Version:  2.0.1
             Keywords:            |               Blocked By:
             Blocking:            |  Reproduced by developer:  0
Analyzed by developer:  0         |
----------------------------------+----------------------------------
 Summary of the bug:
 Trying to convert GIF file to webm after editing in ImageMagick library
 and getting this error. Original gif file converts without errors, but if
 I just open and save it with ImageMagick (or gifsicle) library it doesn't
 convert with ffmpeg anymore.

 In ffmpeg 1.2.1 it's okay and I found that in ffmpeg 2.0.1 some additional
 error checkings were added to libavformat/gifdec.c:
 {{{
     if ((ret >= 0 && !frame_parsed) || ret == AVERROR_EOF) {
         /* This might happen when there is no image block
          * between extension blocks and GIF_TRAILER or EOF */
         if (!gdc->ignore_loop && (block_label == GIF_TRAILER ||
 url_feof(pb))
             && (gdc->total_iter < 0 || ++gdc->iter_count <
 gdc->total_iter))
             return avio_seek(pb, 0, SEEK_SET);
         return AVERROR_EOF;
     } else
         return ret;
 }}}

 So, I'm trying to understand, where is the problem: on ffmpeg side or it's
 ImageMagick (and other libs) GIF saving issue?

 How to reproduce:
 {{{
 % ffmpeg -i processed.gif -b:v 600K -qmin 0 -qmax 50 -crf 5 out.webm
 ffmpeg version 2.0.1 Copyright (c) 2000-2013 the FFmpeg developers
   built on Sep 25 2013 06:03:35 with Apple clang version 4.1
 (tags/Apple/clang-421.11.66) (based on LLVM 3.1svn)
   configuration: --prefix=/opt/local --enable-swscale --enable-avfilter
 --enable-avresample --enable-libmp3lame --enable-libvorbis --enable-
 libopus --enable-libtheora --enable-libschroedinger --enable-libopenjpeg
 --enable-libmodplug --enable-libvpx --enable-libspeex --enable-libass
 --enable-libbluray --enable-gnutls --enable-libfreetype --disable-
 outdev=xv --mandir=/opt/local/share/man --enable-shared --enable-pthreads
 --cc=/usr/bin/clang --arch=x86_64 --enable-yasm --enable-gpl --enable-
 postproc --enable-libx264 --enable-libxvid
   libavutil      52. 38.100 / 52. 38.100
   libavcodec     55. 18.102 / 55. 18.102
   libavformat    55. 12.100 / 55. 12.100
   libavdevice    55.  3.100 / 55.  3.100
   libavfilter     3. 79.101 /  3. 79.101
   libavresample   1.  1.  0 /  1.  1.  0
   libswscale      2.  3.100 /  2.  3.100
   libswresample   0. 17.102 /  0. 17.102
   libpostproc    52.  3.100 / 52.  3.100
 [gif @ 0x7fa121029800] invalid block label
 Input #0, gif, from 'processed.gif':
   Duration: N/A, bitrate: N/A
     Stream #0:0: Video: gif, bgra, 300x198, 100 tbr, 100 tbn, 100 tbc
 [libvpx @ 0x7fa12102a400] v1.1.0
 Output #0, webm, to 'out.webm':
   Metadata:
     encoder         : Lavf55.12.100
     Stream #0:0: Video: vp8 (libvpx), yuva420p, 300x198, q=0-50, 600 kb/s,
 1k tbn, 100 tbc
 Stream mapping:
   Stream #0:0 -> #0:0 (gif -> libvpx)
 Press [q] to stop, [?] for help
 frame=    0 fps=0.0 q=0.0 Lsize=       0kB time=00:00:00.00 bitrate=N/A
 video:0kB audio:0kB subtitle:0 global headers:0kB muxing overhead inf%
 Output file is empty, nothing was encoded (check -ss / -t / -frames
 parameters if used)
 }}}

-- 
Ticket URL: <https://ffmpeg.org/trac/ffmpeg/ticket/3021>
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