FFmpeg 在延时转换期间卡在第 0 帧，开始时间为 `-ss`

Question

我有一个很长的视频，我想把它加速成延时。在FFmpeg wiki 之后，我想出了这个咒语：

ffmpeg -i IMG_0238.MOV -r 60 -ss 00:04:41 -filter:v "setpts=PTS/60.0" -an output.mp4

它应该剪掉最初的几分钟，然后以 60 倍的速度创建一个新的 60fps 视频文件。

虽然它将我所有的 CPU 核心旋转到 100%，但状态栏只是显示frame= 0 fps=0.0 q=0.0 size= 0kB time=00:00:00.00 bitrate=N/A speed= 0x并且永远不会进展。

问题似乎与-ss 00:04:41指定开始时间的标志有关；我想删除源视频的前 4 分 41 秒。当我省略此选项时，视频转换成功。

完整日志如下。

---

ffmpeg version 3.4.1 Copyright (c) 2000-2017 the FFmpeg developers
  built with Apple LLVM version 9.1.0 (clang-902.0.30)
  configuration: --prefix=/usr/local/Cellar/ffmpeg/3.4.1 --enable-shared --enable-pthreads --enable-version3 --enable-hardcoded-tables --enable-avresample --cc=clang --host-cflags= --host-ldflags= --enable-gpl --enable-libmp3lame --enable-libx264 --enable-libx265 --enable-libxvid --enable-opencl --enable-videotoolbox --disable-lzma
  libavutil      55. 78.100 / 55. 78.100
  libavcodec     57.107.100 / 57.107.100
  libavformat    57. 83.100 / 57. 83.100
  libavdevice    57. 10.100 / 57. 10.100
  libavfilter     6.107.100 /  6.107.100
  libavresample   3.  7.  0 /  3.  7.  0
  libswscale      4.  8.100 /  4.  8.100
  libswresample   2.  9.100 /  2.  9.100
  libpostproc    54.  7.100 / 54.  7.100
[mov,mp4,m4a,3gp,3g2,mj2 @ 0x7fb59b800000] stream 2, missing mandatory atoms, broken header
[mov,mp4,m4a,3gp,3g2,mj2 @ 0x7fb59b800000] stream 3, missing mandatory atoms, broken header
Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'IMG_0238.MOV':
  Metadata:
    major_brand     : qt  
    minor_version   : 0
    compatible_brands: qt  
    creation_time   : 2017-04-20T16:25:14.000000Z
    com.apple.quicktime.location.ISO6709: +36.4610+025.3727+123.613/
    com.apple.quicktime.make: Apple
    com.apple.quicktime.model: iPhone 7
    com.apple.quicktime.software: 10.3.1
    com.apple.quicktime.creationdate: 2017-04-20T19:25:13+0300
  Duration: 01:22:45.53, start: -0.000023, bitrate: 44171 kb/s
    Stream #0:0(und): Video: h264 (High) (avc1 / 0x31637661), yuv420p(tv, bt709), 3840x2160, 44077 kb/s, 30 fps, 30 tbr, 600 tbn, 1200 tbc (default)
    Metadata:
      rotate          : 180
      creation_time   : 2017-04-20T16:25:14.000000Z
      handler_name    : Core Media Data Handler
      encoder         : H.264
    Side data:
      displaymatrix: rotation of -180.00 degrees
    Stream #0:1(und): Audio: aac (LC) (mp4a / 0x6134706D), 44100 Hz, mono, fltp, 84 kb/s (default)
    Metadata:
      creation_time   : 2017-04-20T16:25:14.000000Z
      handler_name    : Core Media Data Handler
    Stream #0:2(und): Data: none (mebx / 0x7862656D) (default)
    Metadata:
      creation_time   : 2017-04-20T16:25:14.000000Z
      handler_name    : Core Media Data Handler
    Stream #0:3(und): Data: none (mebx / 0x7862656D) (default)
    Metadata:
      creation_time   : 2017-04-20T16:25:14.000000Z
      handler_name    : Core Media Data Handler
File 'output.mp4' already exists. Overwrite ? [y/N] y
Stream mapping:
  Stream #0:0 -> #0:0 (h264 (native) -> h264 (libx264))
Press [q] to stop, [?] for help
[libx264 @ 0x7fb59b82b800] using cpu capabilities: MMX2 SSE2Fast SSSE3 SSE4.2 AVX FMA3 AVX2 LZCNT BMI2
[libx264 @ 0x7fb59b82b800] profile High, level 5.2
[libx264 @ 0x7fb59b82b800] 264 - core 148 r2795 aaa9aa8 - H.264/MPEG-4 AVC codec - Copyleft 2003-2017 - http://www.videolan.org/x264.html - options: cabac=1 ref=3 deblock=1:0:0 analyse=0x3:0x113 me=hex subme=7 psy=1 psy_rd=1.00:0.00 mixed_ref=1 me_range=16 chroma_me=1 trellis=1 8x8dct=1 cqm=0 deadzone=21,11 fast_pskip=1 chroma_qp_offset=-2 threads=6 lookahead_threads=1 sliced_threads=0 nr=0 decimate=1 interlaced=0 bluray_compat=0 constrained_intra=0 bframes=3 b_pyramid=2 b_adapt=1 b_bias=0 direct=1 weightb=1 open_gop=0 weightp=2 keyint=250 keyint_min=25 scenecut=40 intra_refresh=0 rc_lookahead=40 rc=crf mbtree=1 crf=23.0 qcomp=0.60 qpmin=0 qpmax=69 qpstep=4 ip_ratio=1.40 aq=1:1.00
Output #0, mp4, to 'output.mp4':
  Metadata:
    major_brand     : qt  
    minor_version   : 0
    compatible_brands: qt  
    com.apple.quicktime.creationdate: 2017-04-20T19:25:13+0300
    com.apple.quicktime.location.ISO6709: +36.4610+025.3727+123.613/
    com.apple.quicktime.make: Apple
    com.apple.quicktime.model: iPhone 7
    com.apple.quicktime.software: 10.3.1
    encoder         : Lavf57.83.100
    Stream #0:0(und): Video: h264 (libx264) (avc1 / 0x31637661), yuv420p, 3840x2160, q=-1--1, 60 fps, 15360 tbn, 60 tbc (default)
    Metadata:
      encoder         : Lavc57.107.100 libx264
      creation_time   : 2017-04-20T16:25:14.000000Z
      handler_name    : Core Media Data Handler
    Side data:
      cpb: bitrate max/min/avg: 0/0/0 buffer size: 0 vbv_delay: -1
      displaymatrix: rotation of -0.00 degrees
frame=    0 fps=0.0 q=0.0 size=       0kB time=00:00:00.00 bitrate=N/A speed=   0x

Answer 1

在-ss参数前指定-i参数：

ffmpeg -ss 00:04:41 -i IMG_0238.MOV -r 60 -filter:v "setpts=PTS/60.0" -an output.mp4

什么-ss作为输出选项确实是丢弃输出，直到接收到与指定的入点帧。由于这可能需要一些时间，进度计数器将显示为“卡住”，但处理仍在进行中。对你来说，什么又进一步增加了问题是因为你崩溃时间戳〜1/60，ss的04:41代表04:41 x 60的输入被丢弃。大大增加了进度延迟，但更重要的是，您的输出不会从您想要的地方开始。

通过使用-ss作为输入选项，ffmpeg 将丢弃04:41输入，然后处理其余部分。进度计数器也将立即激活。