Question

我想使用调色板从ffmpeg（ffmpeg version 2.8.15-0ubuntu0.16.04.1）的mp4电影中生成gif。如果我不使用调色板，一切都可以正常工作：

$ ffmpeg -i in.mp4 -filter_complex "scale=160:-1" out.gif
...
frame= 2003 fps=251 q=-0.0 Lsize=   21172kB time=00:01:20.12 bitrate=2164.7kbits/s    
video:21155kB audio:0kB subtitle:0kB other streams:0kB global headers:0kB muxing overhead: 0.077667%

但是使用这样的调色板会导致Buffer queue overflow, dropping消息和视频被截断

$ ffmpeg -i in.mp4 -filter_complex "[0:v] scale=160:-1, split [a][b];[a] palettegen [p];[b][p] paletteuse" out.gif
....
[Parsed_paletteuse_3 @ 0xc56de0] [framesync @ 0xd1af08] Buffer queue overflow, dropping.
Last message repeated 36 times
[Parsed_paletteuse_3 @ 0xc56de0] [framesync @ 0xd1af08] Buffer queue overflow, dropping.
Last message repeated 106 times
...
[Parsed_palettegen_2 @ 0xc56d40] 255(+1) colors generated out of 1347441 colors; ratio=0.000189
frame=   65 fps=5.4 q=-0.0 Lsize=    1036kB time=00:01:20.12 bitrate= 105.9kbits/s    
video:1035kB audio:0kB subtitle:0kB other streams:0kB global headers:0kB muxing overhead: 0.124664%

Answer 1

同时，我弄清楚了如何规避此行为。我只需要在用于转换的流中包含一个fifo，这样它就可以等到生成调色板为止：

$ ffmpeg -i in.mp4 -filter_complex "[0:v] scale=160:-1 [r];[r] split [a][b];[b]fifo[bb]; [a] palettegen [p];[bb][p] paletteuse" out.gif
...
frame= 2003 fps=7.8 q=-0.0 Lsize=  804608kB time=00:01:20.12 bitrate=82268.4kbits/s    
video:804591kB audio:0kB subtitle:0kB other streams:0kB global headers:0kB muxing overhead: 0.002042%

ffmpeg使用调色板将mp4转换为gif会导致视频被截断

1 个答案: