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ffmpeg 尝试删除视频的前几秒

发布于 2024-12-05 00:35:06 字数 6790 浏览 1 评论 0原文

我试图删除视频流前面的几秒钟（音频已排除），但我得到了奇怪的结果：我认为每一秒我都会增加- ss，生成的文件会短一秒......事实似乎并非如此。

original     ==> 01:04:52.84
-ss 19       ==> 01:04:42.84 (diff = 10) [command history shown below]
-ss 20       ==> 01:04:32.84 (diff = 20) [command history shown below]
-ss 21       ==> 01:04:32.84 (diff = 20)
-ss 25       ==> 01:04:32.84 (diff = 20)
-ss 0:0:25.0 ==> 01:04:32.84 (diff = 20)
-ss 0:0:25.5 ==> 01:04:32.84 (diff = 20) [command history shown below]

命令：ffmpeg -ss # -i temp.mp4 -y -vcodec copy temp_croppedFromStart.mp4

这是 19 & 的命令历史记录。 20

# ffmpeg -ss 19 -i temp.mp4 -y -vcodec copy  temp_croppedFromStart.mp4; ffmpeg -i temp.mp4 2>&1 | grep Duration; ffmpeg -i temp_croppedFromStart.mp4 2>&1 | grep Duration
ffmpeg version N-31809-g9acffed, Copyright (c) 2000-2011 the FFmpeg developers
  built on Aug 10 2011 21:25:11 with gcc 4.4.5
  configuration: --enable-gpl --enable-version3 --enable-nonfree --enable-postproc --enable-libfaac --enable-libmp3lame --enable-libopencore-amrnb --enable-libopencore-amrwb --enable-libtheora --enable-libvorbis --enable-libvpx --enable-libx264 --enable-libxvid --enable-x11grab
  libavutil    51. 11. 1 / 51. 11. 1
  libavcodec   53. 10. 0 / 53. 10. 0
  libavformat  53.  6. 0 / 53.  6. 0
  libavdevice  53.  2. 0 / 53.  2. 0
  libavfilter   2. 28. 1 /  2. 28. 1
  libswscale    2.  0. 0 /  2.  0. 0
  libpostproc  51.  2. 0 / 51.  2. 0
Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'temp.mp4':
  Metadata:
    major_brand     : isom
    minor_version   : 512
    compatible_brands: isomiso2avc1mp41
    creation_time   : 1970-01-01 00:00:00
    encoder         : Lavf53.6.0
  Duration: 01:04:52.84, start: 0.000000, bitrate: 553 kb/s
    Stream #0.0(und): Video: h264 (Constrained Baseline), yuv420p, 960x640, 552 kb/s, 25 fps, 25 tbr, 25 tbn, 50 tbc
    Metadata:
      creation_time   : 1970-01-01 00:00:00
Output #0, mp4, to 'temp_croppedFromStart.mp4':
  Metadata:
    major_brand     : isom
    minor_version   : 512
    compatible_brands: isomiso2avc1mp41
    creation_time   : 1970-01-01 00:00:00
    encoder         : Lavf53.6.0
    Stream #0.0(und): Video: libx264, yuv420p, 960x640, q=2-31, 552 kb/s, 25 tbn, 25 tbc
    Metadata:
      creation_time   : 1970-01-01 00:00:00
Stream mapping:
  Stream #0.0 -> #0.0
Press [q] to stop, [?] for help
frame=97071 fps=42523 q=-1.0 Lsize=  262684kB time=01:04:33.84 bitrate= 555.5kbits/s
video:261923kB audio:0kB global headers:0kB muxing overhead 0.290418%
  Duration: 01:04:52.84, start: 0.000000, bitrate: 553 kb/s
  Duration: 01:04:42.84, start: 0.000000, bitrate: 554 kb/s


# ffmpeg -ss 20 -i temp.mp4 -y -vcodec copy  temp_croppedFromStart.mp4; ffmpeg -i temp.mp4 2>&1 | grep Duration; ffmpeg -i temp_croppedFromStart.mp4 2>&1 | grep Duration
ffmpeg version N-31809-g9acffed, Copyright (c) 2000-2011 the FFmpeg developers
  built on Aug 10 2011 21:25:11 with gcc 4.4.5
  configuration: --enable-gpl --enable-version3 --enable-nonfree --enable-postproc --enable-libfaac --enable-libmp3lame --enable-libopencore-amrnb --enable-libopencore-amrwb --enable-libtheora --enable-libvorbis --enable-libvpx --enable-libx264 --enable-libxvid --enable-x11grab
  libavutil    51. 11. 1 / 51. 11. 1
  libavcodec   53. 10. 0 / 53. 10. 0
  libavformat  53.  6. 0 / 53.  6. 0
  libavdevice  53.  2. 0 / 53.  2. 0
  libavfilter   2. 28. 1 /  2. 28. 1
  libswscale    2.  0. 0 /  2.  0. 0
  libpostproc  51.  2. 0 / 51.  2. 0
Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'temp.mp4':
  Metadata:
    major_brand     : isom
    minor_version   : 512
    compatible_brands: isomiso2avc1mp41
    creation_time   : 1970-01-01 00:00:00
    encoder         : Lavf53.6.0
  Duration: 01:04:52.84, start: 0.000000, bitrate: 553 kb/s
    Stream #0.0(und): Video: h264 (Constrained Baseline), yuv420p, 960x640, 552 kb/s, 25 fps, 25 tbr, 25 tbn, 50 tbc
    Metadata:
      creation_time   : 1970-01-01 00:00:00
Output #0, mp4, to 'temp_croppedFromStart.mp4':
  Metadata:
    major_brand     : isom
    minor_version   : 512
    compatible_brands: isomiso2avc1mp41
    creation_time   : 1970-01-01 00:00:00
    encoder         : Lavf53.6.0
    Stream #0.0(und): Video: libx264, yuv420p, 960x640, q=2-31, 552 kb/s, 25 tbn, 25 tbc
    Metadata:
      creation_time   : 1970-01-01 00:00:00
Stream mapping:
  Stream #0.0 -> #0.0
Press [q] to stop, [?] for help
frame=96821 fps=47168 q=-1.0 Lsize=  262003kB time=01:04:32.84 bitrate= 554.2kbits/s
video:261244kB audio:0kB global headers:0kB muxing overhead 0.290410%
  Duration: 01:04:52.84, start: 0.000000, bitrate: 553 kb/s
  Duration: 01:04:32.84, start: 0.000000, bitrate: 554 kb/s

# ffmpeg -ss 0:0:25.5 -i temp.mp4 -y -vcodec copy  temp_croppedFromStart.mp4; ffmpeg -i temp.mp4 2>&1 | grep Duration; ffmpeg -i temp_croppedFromStart.mp4 2>&1 | grep Duration
ffmpeg version N-31809-g9acffed, Copyright (c) 2000-2011 the FFmpeg developers
  built on Aug 10 2011 21:25:11 with gcc 4.4.5
  configuration: --enable-gpl --enable-version3 --enable-nonfree --enable-postproc --enable-libfaac --enable-libmp3lame --enable-libopencore-amrnb --enable-libopencore-amrwb --enable-libtheora --enable-libvorbis --enable-libvpx --enable-libx264 --enable-libxvid --enable-x11grab
  libavutil    51. 11. 1 / 51. 11. 1
  libavcodec   53. 10. 0 / 53. 10. 0
  libavformat  53.  6. 0 / 53.  6. 0
  libavdevice  53.  2. 0 / 53.  2. 0
  libavfilter   2. 28. 1 /  2. 28. 1
  libswscale    2.  0. 0 /  2.  0. 0
  libpostproc  51.  2. 0 / 51.  2. 0
Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'temp.mp4':
  Metadata:
    major_brand     : isom
    minor_version   : 512
    compatible_brands: isomiso2avc1mp41
    creation_time   : 1970-01-01 00:00:00
    encoder         : Lavf53.6.0
  Duration: 01:04:52.84, start: 0.000000, bitrate: 553 kb/s
    Stream #0.0(und): Video: h264 (Constrained Baseline), yuv420p, 960x640, 552 kb/s, 25 fps, 25 tbr, 25 tbn, 50 tbc
    Metadata:
      creation_time   : 1970-01-01 00:00:00
Output #0, mp4, to 'temp_croppedFromStart.mp4':
  Metadata:
    major_brand     : isom
    minor_version   : 512
    compatible_brands: isomiso2avc1mp41
    creation_time   : 1970-01-01 00:00:00
    encoder         : Lavf53.6.0
    Stream #0.0(und): Video: libx264, yuv420p, 960x640, q=2-31, 552 kb/s, 25 tbn, 25 tbc
    Metadata:
      creation_time   : 1970-01-01 00:00:00
Stream mapping:
  Stream #0.0 -> #0.0
Press [q] to stop, [?] for help
frame=96821 fps=45920 q=-1.0 Lsize=  262003kB time=01:04:27.32 bitrate= 555.0kbits/s
video:261244kB audio:0kB global headers:0kB muxing overhead 0.290424%
  Duration: 01:04:52.84, start: 0.000000, bitrate: 553 kb/s
  Duration: 01:04:32.84, start: 0.000000, bitrate: 554 kb/s
原文

I'm trying to remove a few seconds off the front of a video stream (audio already excluded), and I'm getting strange results: I would think that for every second I increase -ss by, the resulting file would be a second shorter... that doesn't seem to be the case.

original     ==> 01:04:52.84
-ss 19       ==> 01:04:42.84 (diff = 10) [command history shown below]
-ss 20       ==> 01:04:32.84 (diff = 20) [command history shown below]
-ss 21       ==> 01:04:32.84 (diff = 20)
-ss 25       ==> 01:04:32.84 (diff = 20)
-ss 0:0:25.0 ==> 01:04:32.84 (diff = 20)
-ss 0:0:25.5 ==> 01:04:32.84 (diff = 20) [command history shown below]

Command: ffmpeg -ss # -i temp.mp4 -y -vcodec copy temp_croppedFromStart.mp4

Here's the command history for 19 & 20

# ffmpeg -ss 19 -i temp.mp4 -y -vcodec copy  temp_croppedFromStart.mp4; ffmpeg -i temp.mp4 2>&1 | grep Duration; ffmpeg -i temp_croppedFromStart.mp4 2>&1 | grep Duration
ffmpeg version N-31809-g9acffed, Copyright (c) 2000-2011 the FFmpeg developers
  built on Aug 10 2011 21:25:11 with gcc 4.4.5
  configuration: --enable-gpl --enable-version3 --enable-nonfree --enable-postproc --enable-libfaac --enable-libmp3lame --enable-libopencore-amrnb --enable-libopencore-amrwb --enable-libtheora --enable-libvorbis --enable-libvpx --enable-libx264 --enable-libxvid --enable-x11grab
  libavutil    51. 11. 1 / 51. 11. 1
  libavcodec   53. 10. 0 / 53. 10. 0
  libavformat  53.  6. 0 / 53.  6. 0
  libavdevice  53.  2. 0 / 53.  2. 0
  libavfilter   2. 28. 1 /  2. 28. 1
  libswscale    2.  0. 0 /  2.  0. 0
  libpostproc  51.  2. 0 / 51.  2. 0
Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'temp.mp4':
  Metadata:
    major_brand     : isom
    minor_version   : 512
    compatible_brands: isomiso2avc1mp41
    creation_time   : 1970-01-01 00:00:00
    encoder         : Lavf53.6.0
  Duration: 01:04:52.84, start: 0.000000, bitrate: 553 kb/s
    Stream #0.0(und): Video: h264 (Constrained Baseline), yuv420p, 960x640, 552 kb/s, 25 fps, 25 tbr, 25 tbn, 50 tbc
    Metadata:
      creation_time   : 1970-01-01 00:00:00
Output #0, mp4, to 'temp_croppedFromStart.mp4':
  Metadata:
    major_brand     : isom
    minor_version   : 512
    compatible_brands: isomiso2avc1mp41
    creation_time   : 1970-01-01 00:00:00
    encoder         : Lavf53.6.0
    Stream #0.0(und): Video: libx264, yuv420p, 960x640, q=2-31, 552 kb/s, 25 tbn, 25 tbc
    Metadata:
      creation_time   : 1970-01-01 00:00:00
Stream mapping:
  Stream #0.0 -> #0.0
Press [q] to stop, [?] for help
frame=97071 fps=42523 q=-1.0 Lsize=  262684kB time=01:04:33.84 bitrate= 555.5kbits/s
video:261923kB audio:0kB global headers:0kB muxing overhead 0.290418%
  Duration: 01:04:52.84, start: 0.000000, bitrate: 553 kb/s
  Duration: 01:04:42.84, start: 0.000000, bitrate: 554 kb/s


# ffmpeg -ss 20 -i temp.mp4 -y -vcodec copy  temp_croppedFromStart.mp4; ffmpeg -i temp.mp4 2>&1 | grep Duration; ffmpeg -i temp_croppedFromStart.mp4 2>&1 | grep Duration
ffmpeg version N-31809-g9acffed, Copyright (c) 2000-2011 the FFmpeg developers
  built on Aug 10 2011 21:25:11 with gcc 4.4.5
  configuration: --enable-gpl --enable-version3 --enable-nonfree --enable-postproc --enable-libfaac --enable-libmp3lame --enable-libopencore-amrnb --enable-libopencore-amrwb --enable-libtheora --enable-libvorbis --enable-libvpx --enable-libx264 --enable-libxvid --enable-x11grab
  libavutil    51. 11. 1 / 51. 11. 1
  libavcodec   53. 10. 0 / 53. 10. 0
  libavformat  53.  6. 0 / 53.  6. 0
  libavdevice  53.  2. 0 / 53.  2. 0
  libavfilter   2. 28. 1 /  2. 28. 1
  libswscale    2.  0. 0 /  2.  0. 0
  libpostproc  51.  2. 0 / 51.  2. 0
Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'temp.mp4':
  Metadata:
    major_brand     : isom
    minor_version   : 512
    compatible_brands: isomiso2avc1mp41
    creation_time   : 1970-01-01 00:00:00
    encoder         : Lavf53.6.0
  Duration: 01:04:52.84, start: 0.000000, bitrate: 553 kb/s
    Stream #0.0(und): Video: h264 (Constrained Baseline), yuv420p, 960x640, 552 kb/s, 25 fps, 25 tbr, 25 tbn, 50 tbc
    Metadata:
      creation_time   : 1970-01-01 00:00:00
Output #0, mp4, to 'temp_croppedFromStart.mp4':
  Metadata:
    major_brand     : isom
    minor_version   : 512
    compatible_brands: isomiso2avc1mp41
    creation_time   : 1970-01-01 00:00:00
    encoder         : Lavf53.6.0
    Stream #0.0(und): Video: libx264, yuv420p, 960x640, q=2-31, 552 kb/s, 25 tbn, 25 tbc
    Metadata:
      creation_time   : 1970-01-01 00:00:00
Stream mapping:
  Stream #0.0 -> #0.0
Press [q] to stop, [?] for help
frame=96821 fps=47168 q=-1.0 Lsize=  262003kB time=01:04:32.84 bitrate= 554.2kbits/s
video:261244kB audio:0kB global headers:0kB muxing overhead 0.290410%
  Duration: 01:04:52.84, start: 0.000000, bitrate: 553 kb/s
  Duration: 01:04:32.84, start: 0.000000, bitrate: 554 kb/s

# ffmpeg -ss 0:0:25.5 -i temp.mp4 -y -vcodec copy  temp_croppedFromStart.mp4; ffmpeg -i temp.mp4 2>&1 | grep Duration; ffmpeg -i temp_croppedFromStart.mp4 2>&1 | grep Duration
ffmpeg version N-31809-g9acffed, Copyright (c) 2000-2011 the FFmpeg developers
  built on Aug 10 2011 21:25:11 with gcc 4.4.5
  configuration: --enable-gpl --enable-version3 --enable-nonfree --enable-postproc --enable-libfaac --enable-libmp3lame --enable-libopencore-amrnb --enable-libopencore-amrwb --enable-libtheora --enable-libvorbis --enable-libvpx --enable-libx264 --enable-libxvid --enable-x11grab
  libavutil    51. 11. 1 / 51. 11. 1
  libavcodec   53. 10. 0 / 53. 10. 0
  libavformat  53.  6. 0 / 53.  6. 0
  libavdevice  53.  2. 0 / 53.  2. 0
  libavfilter   2. 28. 1 /  2. 28. 1
  libswscale    2.  0. 0 /  2.  0. 0
  libpostproc  51.  2. 0 / 51.  2. 0
Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'temp.mp4':
  Metadata:
    major_brand     : isom
    minor_version   : 512
    compatible_brands: isomiso2avc1mp41
    creation_time   : 1970-01-01 00:00:00
    encoder         : Lavf53.6.0
  Duration: 01:04:52.84, start: 0.000000, bitrate: 553 kb/s
    Stream #0.0(und): Video: h264 (Constrained Baseline), yuv420p, 960x640, 552 kb/s, 25 fps, 25 tbr, 25 tbn, 50 tbc
    Metadata:
      creation_time   : 1970-01-01 00:00:00
Output #0, mp4, to 'temp_croppedFromStart.mp4':
  Metadata:
    major_brand     : isom
    minor_version   : 512
    compatible_brands: isomiso2avc1mp41
    creation_time   : 1970-01-01 00:00:00
    encoder         : Lavf53.6.0
    Stream #0.0(und): Video: libx264, yuv420p, 960x640, q=2-31, 552 kb/s, 25 tbn, 25 tbc
    Metadata:
      creation_time   : 1970-01-01 00:00:00
Stream mapping:
  Stream #0.0 -> #0.0
Press [q] to stop, [?] for help
frame=96821 fps=45920 q=-1.0 Lsize=  262003kB time=01:04:27.32 bitrate= 555.0kbits/s
video:261244kB audio:0kB global headers:0kB muxing overhead 0.290424%
  Duration: 01:04:52.84, start: 0.000000, bitrate: 553 kb/s
  Duration: 01:04:32.84, start: 0.000000, bitrate: 554 kb/s

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她说她爱他 2024-12-12 00:35:06

如果不重新编码，您只能在 I 帧处进行剪切。您的 I 帧看起来相隔 10 秒，这相当长，但并非闻所未闻。

您可以在此处阅读有关 I 帧的更多信息：http://en.wikipedia.org/wiki/视频压缩图片类型

Without re-encoding, you can only cut at an I-frame. Your I-frames look to be 10 seconds apart, which is rather long, but not unheard of.

You can read more about what an I-frame is here: http://en.wikipedia.org/wiki/Video_compression_picture_types

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