关于ffmpeg修剪有很多问题，但可以找到一个相关的问题。
我正在从时间x到时间x + 30修剪视频。我要做的是
> ffmpeg -ss 127 -i test_video_2.mp4 -t 30 -c copy test_video_2_ssi_to.mp4
ffmpeg version 2.8.12 Copyright (c) 2000-2017 the FFmpeg developers
built with gcc 7.3.0 (GCC)
libavutil 54. 31.100 / 54. 31.100
libavcodec 56. 60.100 / 56. 60.100
libavformat 56. 40.101 / 56. 40.101
libavdevice 56. 4.100 / 56. 4.100
libavfilter 5. 40.101 / 5. 40.101 libswscale 3. 1.101 / 3. 1.101
libswresample 1. 2.101 / 1. 2.101
libpostproc 53. 3.100 / 53. 3.100
[aac @ 0x655000] element type mismatch 1 != 0
Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'test_video_2.mp4':
Metadata:
major_brand :
minor_version :
compatible_brands:
encoder :
Duration: 00:17:59.63, start: 0.000000, bitrate: 436 kb/s
Stream #0:0(und): Video: h264 (Main) (avc1 / 0x31637661), yuv420p, 640x360, 365 kb/s, 30 fps, 30 tbr, 16k tbn, 6
0 tbc (default)
Metadata:
handler_name : VideoHandler
Stream #0:1(und): Audio: aac (HE-AAC) (mp4a / 0x6134706D), 48000 Hz, stereo, fltp, 63 kb/s (default)
Metadata:
handler_name : SoundHandler
[mp4 @ 0x682a60] Codec for stream 0 does not use global headers but container format requires global headers
[mp4 @ 0x682a60] Codec for stream 1 does not use global headers but container format requires global headers
Output #0, mp4, to 'test_video_2_ssi_to.mp4':
Metadata:
major_brand :
minor_version :
compatible_brands:
encoder :
Stream #0:0(und): Video: h264 ([33][0][0][0] / 0x0021), yuv420p, 640x360, q=2-31, 365 kb/s, 30 fps, 30 tbr, 16k
tbn, 16k tbc (default)
Metadata:
handler_name : VideoHandler
Stream #0:1(und): Audio: aac ([64][0][0][0] / 0x0040), 48000 Hz, stereo, 63 kb/s (default)
Metadata: handler_name : SoundHandler
Stream mapping:
Stream #0:0 -> #0:0 (copy)
Stream #0:1 -> #0:1 (copy)
Press [q] to stop, [?] for help
frame= 1110 fps=0.0 q=-1.0 Lsize= 1552kB time=00:00:30.01 bitrate= 423.7kbits/s
video:1227kB audio:289kB subtitle:0kB other streams:0kB global headers:0kB muxing overhead: 2.351015%
日志显示输出持续时间为30秒，但输出文件为37秒，最后7秒没有更多帧和音频。我怀疑这可能与关键帧有关，但似乎无法调试。
> ffprobe test_video_2_ssi_to.mp4
ffprobe version 2.8.12 Copyright (c) 2007-2017 the FFmpeg developers
built with gcc 7.3.0 (GCC)
libavutil 54. 31.100 / 54. 31.100
libavcodec 56. 60.100 / 56. 60.100
libavformat 56. 40.101 / 56. 40.101
libavdevice 56. 4.100 / 56. 4.100
libavfilter 5. 40.101 / 5. 40.101
libswscale 3. 1.101 / 3. 1.101
libswresample 1. 2.101 / 1. 2.101
libpostproc 53. 3.100 / 53. 3.100
[aac @ 0x641e40] element type mismatch 1 != 0
Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'test_video_2_ssi_to.mp4':
Metadata:
major_brand : isom
minor_version : 512
compatible_brands: isomiso2avc1mp41
encoder : Lavf56.40.101
Duration: 00:00:37.04, start: -7.021333, bitrate: 343 kb/s
Stream #0:0(und): Video: h264 (Main) (avc1 / 0x31637661), yuv420p, 640x360, 271 kb/s, 30 fps, 30 tbr, 16k tbn, 60 tbc (default)
Metadata:
handler_name : VideoHandler
Stream #0:1(und): Audio: aac (HE-AAC) (mp4a / 0x6134706D), 48000 Hz, stereo, fltp, 63 kb/s (default)
Metadata:
handler_name : SoundHandler
与其他视频相同，最后花了几秒钟的时间。