Showpalette filter returns default palette for GIF.

[Mulvya]

For the GIF file attached, the showpalette filter returns the default palette. The palettegen filter, in effect, reproduces the embedded palette. See attached PNGs.

Showpalette (only run for 1 frame, but outputting to image sequence has same result):

ffmpeg started on 2017-03-23 at 16:16:47
Report written to "ffmpeg-20170323-161647.log"
Command line:
ffmpeg -i bbb-nodither.gif -vf showpalette -vframes 1 showpalette.png -report
ffmpeg version N-84049-gde1308429a Copyright (c) 2000-2017 the FFmpeg developers
  built with gcc 6.3.0 (Rev2, Built by MSYS2 project)
  configuration:  --enable-avisynth --enable-libmp3lame --enable-libopus --enable-libvorbis --enable-libvpx --enable-libx264 --enable-libx265 --enable-cuda --enable-cuvid --enable-schannel --enable-decklink --enable-fontconfig --enable-frei0r --enable-libass --enable-libbluray --enable-libbs2b --enable-libcaca --enable-libfreetype --enable-libfribidi --enable-libgme --enable-libgsm --enable-libilbc --enable-libmfx --enable-libmodplug --enable-libopencore-amrnb --enable-libopencore-amrwb --enable-libopenjpeg --enable-librtmp --enable-libschroedinger --enable-libsoxr --enable-libspeex --enable-libtheora --enable-libtwolame --enable-libvidstab --enable-libvo-amrwbenc --enable-libwavpack --enable-libwebp --enable-libxavs --enable-libxvid --enable-libzimg --enable-openssl --enable-libsnappy --enable-gpl --enable-opencl --enable-opengl --enable-libcdio --enable-libfdk-aac --enable-libkvazaar --enable-librubberband --enable-libssh --enable-libtesseract --enable-libzvbi --enable-chromaprint --enable-libopenh264 --en  libavutil      55. 48.100 / 55. 48.100
  libavcodec     57. 83.100 / 57. 83.100
  libavformat    57. 66.104 / 57. 66.104
  libavdevice    57.  3.100 / 57.  3.100
  libavfilter     6. 77.100 /  6. 77.100
  libswscale      4.  3.101 /  4.  3.101
  libswresample   2.  4.100 /  2.  4.100
  libpostproc    54.  2.100 / 54.  2.100
Splitting the commandline.
Reading option '-i' ... matched as input url with argument 'bbb-nodither.gif'.
Reading option '-vf' ... matched as option 'vf' (set video filters) with argument 'showpalette'.
Reading option '-vframes' ... matched as option 'vframes' (set the number of video frames to output) with argument '1'.
Reading option 'showpalette.png' ... matched as output url.
Reading option '-report' ... matched as option 'report' (generate a report) with argument '1'.
Finished splitting the commandline.
Parsing a group of options: global .
Applying option report (generate a report) with argument 1.
Successfully parsed a group of options.
Parsing a group of options: input url bbb-nodither.gif.
Successfully parsed a group of options.
Opening an input file: bbb-nodither.gif.
[file @ 00000000004aa720] Setting default whitelist 'file,crypto'
[gif @ 00000000004a8fe0] Format gif probed with size=2048 and score=100
[gif @ 00000000004a8fe0] Before avformat_find_stream_info() pos: 0 bytes read:32768 seeks:0 nb_streams:1
[gif @ 00000000004a8fe0] rfps: 23.833333 0.012814
[gif @ 00000000004a8fe0] rfps: 23.916667 0.006566
[gif @ 00000000004a8fe0] rfps: 24.000000 0.004757
[gif @ 00000000004a8fe0] rfps: 24.083333 0.007388
[gif @ 00000000004a8fe0] rfps: 24.166667 0.014459
[gif @ 00000000004a8fe0] rfps: 48.000000 0.019029
[gif @ 00000000004a8fe0] rfps: 52.000000 0.019029
[gif @ 00000000004a8fe0] rfps: 23.976024 0.004823
[gif @ 00000000004a8fe0] rfps: 47.952048 0.019291
[gif @ 00000000004a8fe0] After avformat_find_stream_info() pos: 1036665 bytes read:2598949 seeks:2 frames:48
Input #0, gif, from 'bbb-nodither.gif':
  Duration: N/A, bitrate: N/A
    Stream #0:0, 48, 1/100: Video: gif, bgra, 300x169, 23.98 fps, 24 tbr, 100 tbn, 100 tbc
Successfully opened the file.
Parsing a group of options: output url showpalette.png.
Applying option vf (set video filters) with argument showpalette.
Applying option vframes (set the number of video frames to output) with argument 1.
Successfully parsed a group of options.
Opening an output file: showpalette.png.
Successfully opened the file.
Stream mapping:
  Stream #0:0 -> #0:0 (gif (native) -> png (native))
Press [q] to stop, [?] for help
cur_dts is invalid (this is harmless if it occurs once at the start per stream)
[gif @ 00000000031852e0] code=21 '!'
[gif @ 00000000031852e0] code=21 '!'
[gif @ 00000000031852e0] code=2c ','
detected 4 logical cores
[graph 0 input from stream 0:0 @ 00000000004ad1e0] Setting 'video_size' to value '300x169'
[graph 0 input from stream 0:0 @ 00000000004ad1e0] Setting 'pix_fmt' to value '30'
[graph 0 input from stream 0:0 @ 00000000004ad1e0] Setting 'time_base' to value '1/100'
[graph 0 input from stream 0:0 @ 00000000004ad1e0] Setting 'pixel_aspect' to value '0/1'
[graph 0 input from stream 0:0 @ 00000000004ad1e0] Setting 'sws_param' to value 'flags=2'
[graph 0 input from stream 0:0 @ 00000000004ad1e0] Setting 'frame_rate' to value '24/1'
[graph 0 input from stream 0:0 @ 00000000004ad1e0] w:300 h:169 pixfmt:bgra tb:1/100 fr:24/1 sar:0/1 sws_param:flags=2
[format @ 00000000004ad9c0] compat: called with args=[rgb24|rgba|rgb48be|rgba64be|pal8|gray|ya8|gray16be|ya16be|monob]
[format @ 00000000004ad9c0] Setting 'pix_fmts' to value 'rgb24|rgba|rgb48be|rgba64be|pal8|gray|ya8|gray16be|ya16be|monob'
[auto_scaler_0 @ 00000000004ae240] Setting 'flags' to value 'bicubic'
[auto_scaler_0 @ 00000000004ae240] w:iw h:ih flags:'bicubic' interl:0
[Parsed_showpalette_0 @ 00000000004ac840] auto-inserting filter 'auto_scaler_0' between the filter 'graph 0 input from stream 0:0' and the filter 'Parsed_showpalette_0'
[auto_scaler_1 @ 0000000003ad4000] Setting 'flags' to value 'bicubic'
[auto_scaler_1 @ 0000000003ad4000] w:iw h:ih flags:'bicubic' interl:0
[format @ 00000000004ad9c0] auto-inserting filter 'auto_scaler_1' between the filter 'Parsed_showpalette_0' and the filter 'format'
[AVFilterGraph @ 00000000031ea920] query_formats: 4 queried, 1 merged, 2 already done, 0 delayed
[auto_scaler_1 @ 0000000003ad4000] picking rgba out of 9 ref:bgra alpha:1
[swscaler @ 0000000003adcfc0] Forcing full internal H chroma due to input having non subsampled chroma
[auto_scaler_0 @ 00000000004ae240] w:300 h:169 fmt:bgra sar:0/1 -> w:300 h:169 fmt:pal8 sar:0/1 flags:0x4
[swscaler @ 0000000003afc420] Forcing full internal H chroma due to input having non subsampled chroma
[auto_scaler_1 @ 0000000003ad4000] w:480 h:480 fmt:bgra sar:0/1 -> w:480 h:480 fmt:rgba sar:0/1 flags:0x4
Output #0, image2, to 'showpalette.png':
  Metadata:
    encoder         : Lavf57.66.104
    Stream #0:0, 0, 1/24: Video: png, rgba, 480x480, q=2-31, 200 kb/s, 24 fps, 24 tbn, 24 tbc
    Metadata:
      encoder         : Lavc57.83.100 png
Clipping frame in rate conversion by 0.000008
No more output streams to write to, finishing.
[file @ 0000000003ad0320] Setting default whitelist 'file,crypto'
[AVIOContext @ 0000000003b15780] Statistics: 0 seeks, 1 writeouts
frame=    1 fps=0.0 q=-0.0 Lsize=N/A time=00:00:00.04 bitrate=N/A speed=0.316x    
video:5kB audio:0kB subtitle:0kB other streams:0kB global headers:0kB muxing overhead: unknown
Input file #0 (bbb-nodither.gif):
  Input stream #0:0 (video): 1 packets read (38262 bytes); 1 frames decoded; 
  Total: 1 packets (38262 bytes) demuxed
Output file #0 (showpalette.png):
  Output stream #0:0 (video): 1 frames encoded; 1 packets muxed (5567 bytes); 
  Total: 1 packets (5567 bytes) muxed
1 frames successfully decoded, 0 decoding errors
[AVIOContext @ 000000000317bfe0] Statistics: 2598949 bytes read, 2 seeks

Palettegen:

ffmpeg started on 2017-03-23 at 16:19:03
Report written to "ffmpeg-20170323-161903.log"
Command line:
ffmpeg -i bbb-nodither.gif -vf "palettegen,scale=30*iw:-1:flags=neighbor" palettegen.png -report
ffmpeg version N-84049-gde1308429a Copyright (c) 2000-2017 the FFmpeg developers
  built with gcc 6.3.0 (Rev2, Built by MSYS2 project)
  configuration:  --enable-avisynth --enable-libmp3lame --enable-libopus --enable-libvorbis --enable-libvpx --enable-libx264 --enable-libx265 --enable-cuda --enable-cuvid --enable-schannel --enable-decklink --enable-fontconfig --enable-frei0r --enable-libass --enable-libbluray --enable-libbs2b --enable-libcaca --enable-libfreetype --enable-libfribidi --enable-libgme --enable-libgsm --enable-libilbc --enable-libmfx --enable-libmodplug --enable-libopencore-amrnb --enable-libopencore-amrwb --enable-libopenjpeg --enable-librtmp --enable-libschroedinger --enable-libsoxr --enable-libspeex --enable-libtheora --enable-libtwolame --enable-libvidstab --enable-libvo-amrwbenc --enable-libwavpack --enable-libwebp --enable-libxavs --enable-libxvid --enable-libzimg --enable-openssl --enable-libsnappy --enable-gpl --enable-opencl --enable-opengl --enable-libcdio --enable-libfdk-aac --enable-libkvazaar --enable-librubberband --enable-libssh --enable-libtesseract --enable-libzvbi --enable-chromaprint --enable-libopenh264 --en  libavutil      55. 48.100 / 55. 48.100
  libavcodec     57. 83.100 / 57. 83.100
  libavformat    57. 66.104 / 57. 66.104
  libavdevice    57.  3.100 / 57.  3.100
  libavfilter     6. 77.100 /  6. 77.100
  libswscale      4.  3.101 /  4.  3.101
  libswresample   2.  4.100 /  2.  4.100
  libpostproc    54.  2.100 / 54.  2.100
Splitting the commandline.
Reading option '-i' ... matched as input url with argument 'bbb-nodither.gif'.
Reading option '-vf' ... matched as option 'vf' (set video filters) with argument 'palettegen,scale=30*iw:-1:flags=neighbor'.
Reading option 'palettegen.png' ... matched as output url.
Reading option '-report' ... matched as option 'report' (generate a report) with argument '1'.
Finished splitting the commandline.
Parsing a group of options: global .
Applying option report (generate a report) with argument 1.
Successfully parsed a group of options.
Parsing a group of options: input url bbb-nodither.gif.
Successfully parsed a group of options.
Opening an input file: bbb-nodither.gif.
[file @ 000000000054a940] Setting default whitelist 'file,crypto'
[gif @ 0000000000549200] Format gif probed with size=2048 and score=100
[gif @ 0000000000549200] Before avformat_find_stream_info() pos: 0 bytes read:32768 seeks:0 nb_streams:1
[gif @ 0000000000549200] rfps: 23.833333 0.012814
[gif @ 0000000000549200] rfps: 23.916667 0.006566
[gif @ 0000000000549200] rfps: 24.000000 0.004757
[gif @ 0000000000549200] rfps: 24.083333 0.007388
[gif @ 0000000000549200] rfps: 24.166667 0.014459
[gif @ 0000000000549200] rfps: 48.000000 0.019029
[gif @ 0000000000549200] rfps: 52.000000 0.019029
[gif @ 0000000000549200] rfps: 23.976024 0.004823
[gif @ 0000000000549200] rfps: 47.952048 0.019291
[gif @ 0000000000549200] After avformat_find_stream_info() pos: 1036665 bytes read:2598949 seeks:2 frames:48
Input #0, gif, from 'bbb-nodither.gif':
  Duration: N/A, bitrate: N/A
    Stream #0:0, 48, 1/100: Video: gif, bgra, 300x169, 23.98 fps, 24 tbr, 100 tbn, 100 tbc
Successfully opened the file.
Parsing a group of options: output url palettegen.png.
Applying option vf (set video filters) with argument palettegen,scale=30*iw:-1:flags=neighbor.
Successfully parsed a group of options.
Opening an output file: palettegen.png.
Successfully opened the file.
Stream mapping:
  Stream #0:0 -> #0:0 (gif (native) -> png (native))
Press [q] to stop, [?] for help
cur_dts is invalid (this is harmless if it occurs once at the start per stream)
[gif @ 0000000003005320] code=21 '!'
[gif @ 0000000003005320] code=21 '!'
[gif @ 0000000003005320] code=2c ','
detected 4 logical cores
[Parsed_scale_1 @ 000000000054d560] Setting 'w' to value '30*iw'
[Parsed_scale_1 @ 000000000054d560] Setting 'h' to value '-1'
[Parsed_scale_1 @ 000000000054d560] Setting 'flags' to value 'neighbor'
[Parsed_scale_1 @ 000000000054d560] w:30*iw h:-1 flags:'neighbor' interl:0
[graph 0 input from stream 0:0 @ 00000000039cf260] Setting 'video_size' to value '300x169'
[graph 0 input from stream 0:0 @ 00000000039cf260] Setting 'pix_fmt' to value '30'
[graph 0 input from stream 0:0 @ 00000000039cf260] Setting 'time_base' to value '1/100'
[graph 0 input from stream 0:0 @ 00000000039cf260] Setting 'pixel_aspect' to value '0/1'
[graph 0 input from stream 0:0 @ 00000000039cf260] Setting 'sws_param' to value 'flags=2'
[graph 0 input from stream 0:0 @ 00000000039cf260] Setting 'frame_rate' to value '24/1'
[graph 0 input from stream 0:0 @ 00000000039cf260] w:300 h:169 pixfmt:bgra tb:1/100 fr:24/1 sar:0/1 sws_param:flags=2
[format @ 00000000039cf7e0] compat: called with args=[rgb24|rgba|rgb48be|rgba64be|pal8|gray|ya8|gray16be|ya16be|monob]
[format @ 00000000039cf7e0] Setting 'pix_fmts' to value 'rgb24|rgba|rgb48be|rgba64be|pal8|gray|ya8|gray16be|ya16be|monob'
[AVFilterGraph @ 000000000306a940] query_formats: 5 queried, 4 merged, 0 already done, 0 delayed
[Parsed_scale_1 @ 000000000054d560] picking rgba out of 9 ref:bgra alpha:1
[swscaler @ 00000000039d8fc0] Forcing full internal H chroma due to input having non subsampled chroma
[Parsed_scale_1 @ 000000000054d560] w:16 h:16 fmt:bgra sar:1/1 -> w:480 h:480 fmt:rgba sar:1/1 flags:0x10
Output #0, image2, to 'palettegen.png':
  Metadata:
    encoder         : Lavf57.66.104
    Stream #0:0, 0, 1/24: Video: png, rgba, 480x480 [SAR 1:1 DAR 1:1], q=2-31, 200 kb/s, 24 fps, 24 tbn, 24 tbc
    Metadata:
      encoder         : Lavc57.83.100 png
cur_dts is invalid (this is harmless if it occurs once at the start per stream)
[gif @ 0000000003005320] code=21 '!'
[gif @ 0000000003005320] code=2c ','
cur_dts is invalid (this is harmless if it occurs once at the start per stream)
[gif @ 0000000003005320] code=21 '!'
[gif @ 0000000003005320] code=2c ','
cur_dts is invalid (this is harmless if it occurs once at the start per stream)
[gif @ 0000000003005320] code=21 '!'
[gif @ 0000000003005320] code=2c ','
cur_dts is invalid (this is harmless if it occurs once at the start per stream)
[gif @ 0000000003005320] code=21 '!'
[gif @ 0000000003005320] code=2c ','
cur_dts is invalid (this is harmless if it occurs once at the start per stream)
[gif @ 0000000003005320] code=21 '!'
[gif @ 0000000003005320] code=2c ','
cur_dts is invalid (this is harmless if it occurs once at the start per stream)
[gif @ 0000000003005320] code=21 '!'
[gif @ 0000000003005320] code=2c ','
cur_dts is invalid (this is harmless if it occurs once at the start per stream)
[gif @ 0000000003005320] code=21 '!'
[gif @ 0000000003005320] code=2c ','
cur_dts is invalid (this is harmless if it occurs once at the start per stream)
[gif @ 0000000003005320] code=21 '!'
[gif @ 0000000003005320] code=2c ','
cur_dts is invalid (this is harmless if it occurs once at the start per stream)
[gif @ 0000000003005320] code=21 '!'
[gif @ 0000000003005320] code=2c ','
cur_dts is invalid (this is harmless if it occurs once at the start per stream)
[gif @ 0000000003005320] code=21 '!'
[gif @ 0000000003005320] code=2c ','
cur_dts is invalid (this is harmless if it occurs once at the start per stream)
[gif @ 0000000003005320] code=21 '!'
[gif @ 0000000003005320] code=2c ','
cur_dts is invalid (this is harmless if it occurs once at the start per stream)
[gif @ 0000000003005320] code=21 '!'
[gif @ 0000000003005320] code=2c ','
cur_dts is invalid (this is harmless if it occurs once at the start per stream)
[gif @ 0000000003005320] code=21 '!'
[gif @ 0000000003005320] code=2c ','
cur_dts is invalid (this is harmless if it occurs once at the start per stream)
[gif @ 0000000003005320] code=21 '!'
[gif @ 0000000003005320] code=2c ','
cur_dts is invalid (this is harmless if it occurs once at the start per stream)
[gif @ 0000000003005320] code=21 '!'
[gif @ 0000000003005320] code=2c ','
cur_dts is invalid (this is harmless if it occurs once at the start per stream)
[gif @ 0000000003005320] code=21 '!'
[gif @ 0000000003005320] code=2c ','
cur_dts is invalid (this is harmless if it occurs once at the start per stream)
[gif @ 0000000003005320] code=21 '!'
[gif @ 0000000003005320] code=2c ','
cur_dts is invalid (this is harmless if it occurs once at the start per stream)
[gif @ 0000000003005320] code=21 '!'
[gif @ 0000000003005320] code=2c ','
cur_dts is invalid (this is harmless if it occurs once at the start per stream)
[gif @ 0000000003005320] code=21 '!'
[gif @ 0000000003005320] code=2c ','
cur_dts is invalid (this is harmless if it occurs once at the start per stream)
[gif @ 0000000003005320] code=21 '!'
[gif @ 0000000003005320] code=2c ','
cur_dts is invalid (this is harmless if it occurs once at the start per stream)
[gif @ 0000000003005320] code=21 '!'
[gif @ 0000000003005320] code=2c ','
cur_dts is invalid (this is harmless if it occurs once at the start per stream)
[gif @ 0000000003005320] code=21 '!'
[gif @ 0000000003005320] code=2c ','
cur_dts is invalid (this is harmless if it occurs once at the start per stream)
[gif @ 0000000003005320] code=21 '!'
[gif @ 0000000003005320] code=2c ','
cur_dts is invalid (this is harmless if it occurs once at the start per stream)
[gif @ 0000000003005320] code=21 '!'
[gif @ 0000000003005320] code=2c ','
cur_dts is invalid (this is harmless if it occurs once at the start per stream)
[gif @ 0000000003005320] code=21 '!'
[gif @ 0000000003005320] code=2c ','
cur_dts is invalid (this is harmless if it occurs once at the start per stream)
[gif @ 0000000003005320] code=21 '!'
[gif @ 0000000003005320] code=2c ','
cur_dts is invalid (this is harmless if it occurs once at the start per stream)
[gif @ 0000000003005320] code=21 '!'
[gif @ 0000000003005320] code=2c ','
cur_dts is invalid (this is harmless if it occurs once at the start per stream)
[gif @ 0000000003005320] code=21 '!'
[gif @ 0000000003005320] code=2c ','
cur_dts is invalid (this is harmless if it occurs once at the start per stream)
[gif @ 0000000003005320] code=21 '!'
[gif @ 0000000003005320] code=2c ','
cur_dts is invalid (this is harmless if it occurs once at the start per stream)
[gif @ 0000000003005320] code=21 '!'
[gif @ 0000000003005320] code=2c ','
cur_dts is invalid (this is harmless if it occurs once at the start per stream)
[gif @ 0000000003005320] code=21 '!'
[gif @ 0000000003005320] code=2c ','
cur_dts is invalid (this is harmless if it occurs once at the start per stream)
[gif @ 0000000003005320] code=21 '!'
[gif @ 0000000003005320] code=2c ','
cur_dts is invalid (this is harmless if it occurs once at the start per stream)
[gif @ 0000000003005320] code=21 '!'
[gif @ 0000000003005320] code=2c ','
cur_dts is invalid (this is harmless if it occurs once at the start per stream)
[gif @ 0000000003005320] code=21 '!'
[gif @ 0000000003005320] code=2c ','
cur_dts is invalid (this is harmless if it occurs once at the start per stream)
[gif @ 0000000003005320] code=21 '!'
[gif @ 0000000003005320] code=2c ','
cur_dts is invalid (this is harmless if it occurs once at the start per stream)
[gif @ 0000000003005320] code=21 '!'
[gif @ 0000000003005320] code=2c ','
cur_dts is invalid (this is harmless if it occurs once at the start per stream)
[gif @ 0000000003005320] code=21 '!'
[gif @ 0000000003005320] code=2c ','
cur_dts is invalid (this is harmless if it occurs once at the start per stream)
[gif @ 0000000003005320] code=21 '!'
[gif @ 0000000003005320] code=2c ','
cur_dts is invalid (this is harmless if it occurs once at the start per stream)
[gif @ 0000000003005320] code=21 '!'
[gif @ 0000000003005320] code=2c ','
cur_dts is invalid (this is harmless if it occurs once at the start per stream)
[gif @ 0000000003005320] code=21 '!'
[gif @ 0000000003005320] code=2c ','
cur_dts is invalid (this is harmless if it occurs once at the start per stream)
[gif @ 0000000003005320] code=21 '!'
[gif @ 0000000003005320] code=2c ','
cur_dts is invalid (this is harmless if it occurs once at the start per stream)
[gif @ 0000000003005320] code=21 '!'
[gif @ 0000000003005320] code=2c ','
cur_dts is invalid (this is harmless if it occurs once at the start per stream)
[gif @ 0000000003005320] code=21 '!'
[gif @ 0000000003005320] code=2c ','
cur_dts is invalid (this is harmless if it occurs once at the start per stream)
[gif @ 0000000003005320] code=21 '!'
[gif @ 0000000003005320] code=2c ','
cur_dts is invalid (this is harmless if it occurs once at the start per stream)
[gif @ 0000000003005320] code=21 '!'
[gif @ 0000000003005320] code=2c ','
cur_dts is invalid (this is harmless if it occurs once at the start per stream)
[gif @ 0000000003005320] code=21 '!'
[gif @ 0000000003005320] code=2c ','
cur_dts is invalid (this is harmless if it occurs once at the start per stream)
[gif @ 0000000003005320] code=21 '!'
[gif @ 0000000003005320] code=2c ','
cur_dts is invalid (this is harmless if it occurs once at the start per stream)
[Parsed_palettegen_0 @ 000000000054cea0] 255(+1) colors generated out of 255 colors; ratio=1.000000
[swscaler @ 00000000039ee880] Forcing full internal H chroma due to input having non subsampled chroma
[Parsed_scale_1 @ 000000000054d560] w:16 h:16 fmt:bgra sar:0/1 -> w:480 h:480 fmt:rgba sar:0/1 flags:0x10
cur_dts is invalid (this is harmless if it occurs once at the start per stream)
Clipping frame in rate conversion by 0.000008
cur_dts is invalid (this is harmless if it occurs once at the start per stream)
No more output streams to write to, finishing.
[file @ 00000000039d2300] Setting default whitelist 'file,crypto'
[AVIOContext @ 000000000054fca0] Statistics: 0 seeks, 1 writeouts
frame=    1 fps=0.0 q=-0.0 Lsize=N/A time=00:00:00.04 bitrate=N/A speed=0.486x    
video:6kB audio:0kB subtitle:0kB other streams:0kB global headers:0kB muxing overhead: unknown
Input file #0 (bbb-nodither.gif):
  Input stream #0:0 (video): 48 packets read (1036664 bytes); 48 frames decoded; 
  Total: 48 packets (1036664 bytes) demuxed
Output file #0 (palettegen.png):
  Output stream #0:0 (video): 1 frames encoded; 1 packets muxed (6007 bytes); 
  Total: 1 packets (6007 bytes) muxed
48 frames successfully decoded, 0 decoding errors
[AVIOContext @ 0000000002ffc020] Statistics: 2598949 bytes read, 2 seeks

[Mulvya]

source GIF

[Mulvya]

See question on ​Stack Overflow that prompted this ticket. FFmpeg did not identify the GIFs as pal8 but the OP checked the palette in the GIF starting at offset 0xD.

[Carl Eugen Hoyos]

If there were an issue, this would be a regression since 91499f4ee825502677dfc11b00205538720d0513

But FFmpeg does not guarantee to output a particular colour space for a given file (as it does not guarantee a particular audio sample format when decoding a given file), this behaviour isn't part of the API/ABI (this is why API users always have to check the pix_fmt and sample_fmts that encoders need / decoders provide). Note that decoding of the provided file only works since f83657fc, four commits after the requested feature was "broken" / the reported "bug" was introduced.
From FFmpeg's pov, the provided file is not palettized, to get a palette for the given (bgra) file, using the palettegen filter is required. Using the showpalette filter for a file that isn't palettized will show a default filter.

Not closing yet as I don't know if changing the current behaviour of the gif decoder / demuxer is possible or not, this may be a valid feature request.

For future tickets: Please do not provide output files unless specifically asked to, attaching them very often leads to confusion.

[Mulvya]

The reason I believe that this GIF is likely palettized is because the source GIF is provided as an output demo of the palettegen/use filters, and is taken from the ​blog of ubitux who authored those filters. See the section on 'Color mapping and dithering'.

[Clément Bœsch]

Heh.

I believe this is because the Gif decoder outputs RGB instead of PAL8. This is technically a regression since 91499f4ee825502677dfc11b00205538720d0513. I don't remember the rationale behind this decision, but I'd love to see the decoder output PAL8 again.

[Clément Bœsch]

Actually, we may not be able to switch back to PAL8 because a frame can be composed over time with the use of multiple different palettes. And even a single image could be composed of pixels from multiple palettes...