ffmpeg 复制以保留时间戳

我正在尝试修改 HLS 段传输流，并使用 ffmpeg 保留其开始时间。但是，即使提到了 -copyts，输出也不会保留输入文件的 start_time 值。这是我的命令行：

ffmpeg  -i fileSequence1.ts -i x.png -filter_complex '[0:v][1:v]overlay[out]' -map '[out]' -map 0:1 -acodec copy -vsync 0 -vcodec libx264 -streamid 0:257 -streamid 1:258 -copyts -profile:v baseline -level 3 output.ts

start_time 值始终延迟约 2 秒。

/Users/macadmin/>ffmpeg -y -v verbose -i fileSequence0.ts -map 0:0 -vcodec libx264 -copyts -vsync 0 -async 0 output.ts
ffmpeg version 2.5.3 Copyright (c) 2000-2015 the FFmpeg developers
  built on Mar 29 2015 21:31:57 with Apple LLVM version 6.0 (clang-600.0.54) (based on LLVM 3.5svn)
  configuration: --prefix=/usr/local/Cellar/ffmpeg/2.5.3 --enable-shared --enable-pthreads --enable-gpl --enable-version3 --enable-hardcoded-tables --enable-avresample --cc=clang --host-cflags= --host-ldflags= --enable-libx264 --enable-libmp3lame --enable-libvo-aacenc --enable-libxvid --enable-libfreetype --enable-libvorbis --enable-libvpx --enable-libass --enable-ffplay --enable-libfdk-aac --enable-libopus --enable-libquvi --enable-libx265 --enable-nonfree --enable-vda
  libavutil      54. 15.100 / 54. 15.100
  libavcodec     56. 13.100 / 56. 13.100
  libavformat    56. 15.102 / 56. 15.102
  libavdevice    56.  3.100 / 56.  3.100
  libavfilter     5.  2.103 /  5.  2.103
  libavresample   2.  1.  0 /  2.  1.  0
  libswscale      3.  1.101 /  3.  1.101
  libswresample   1.  1.100 /  1.  1.100
  libpostproc    53.  3.100 / 53.  3.100
[h264 @ 0x7fa93b800000] Current profile doesn't provide more RBSP data in PPS, skipping
    Last message repeated 2 times
[mpegts @ 0x7fa93a80da00] max_analyze_duration 5000000 reached at 5000000 microseconds
Input #0, mpegts, from 'fileSequence0.ts':
  Duration: 00:00:09.65, start: 9.952111, bitrate: 412 kb/s
  Program 1 
    Stream #0:0[0x101]: Video: h264 (Constrained Baseline) ([27][0][0][0] / 0x001B), yuv420p, 640x360 (640x368), 25 fps, 25 tbr, 90k tbn, 50 tbc
    Stream #0:1[0x102]: Audio: aac (LC) ([15][0][0][0] / 0x000F), 44100 Hz, stereo, fltp, 101 kb/s
[graph 0 input from stream 0:0 @ 0x7fa93a5229c0] w:640 h:360 pixfmt:yuv420p tb:1/90000 fr:25/1 sar:0/1 sws_param:flags=2
[libx264 @ 0x7fa93b800c00] using cpu capabilities: MMX2 SSE2Fast SSSE3 SSE4.2 AVX
[libx264 @ 0x7fa93b800c00] profile High, level 3.0
[mpegts @ 0x7fa93b800600] muxrate VBR, pcr every 2 pkts, sdt every 200, pat/pmt every 40 pkts
Output #0, mpegts, to 'output.ts':
  Metadata:
    encoder         : Lavf56.15.102
    Stream #0:0: Video: h264 (libx264), yuv420p, 640x360, q=-1--1, 25 fps, 90k tbn, 25 tbc
    Metadata:
      encoder         : Lavc56.13.100 libx264
Stream mapping:
  Stream #0:0 -> #0:0 (h264 (native) -> h264 (libx264))
Press [q] to stop, [?] for help
[NULL @ 0x7fa93b800000] Current profile doesn't provide more RBSP data in PPS, skipping
    Last message repeated 1 times
frame=   87 fps=0.0 q=28.0 size=      91kB time=00:00:11.40 bitrate=  65.0kbits/[NULL @ 0x7fa93b800000] Current profile doesn't provide more RBSP data in PPS, skipping
frame=  152 fps=151 q=28.0 size=     204kB time=00:00:14.00 bitrate= 119.4kbits/[NULL @ 0x7fa93b800000] Current profile doesn't provide more RBSP data in PPS, skipping
frame=  224 fps=148 q=28.0 size=     306kB time=00:00:16.88 bitrate= 148.5kbits/No more output streams to write to, finishing.
frame=  240 fps=125 q=-1.0 Lsize=     392kB time=00:00:19.52 bitrate= 164.6kbits/s    
video:334kB audio:0kB subtitle:0kB other streams:0kB global headers:0kB muxing overhead: 17.347548%
Input file #0 (fileSequence0.ts):
  Input stream #0:0 (video): 240 packets read (360450 bytes); 240 frames decoded; 
  Input stream #0:1 (audio): 0 packets read (0 bytes); 
  Total: 240 packets (360450 bytes) demuxed
Output file #0 (output.ts):
  Output stream #0:0 (video): 240 frames encoded; 240 packets muxed (342204 bytes); 
  Total: 240 packets (342204 bytes) muxed
[libx264 @ 0x7fa93b800c00] frame I:3     Avg QP:15.08  size:  7856
[libx264 @ 0x7fa93b800c00] frame P:81    Avg QP:21.03  size:  2807
[libx264 @ 0x7fa93b800c00] frame B:156   Avg QP:23.40  size:   585
[libx264 @ 0x7fa93b800c00] consecutive B-frames: 11.7%  2.5%  7.5% 78.3%
[libx264 @ 0x7fa93b800c00] mb I  I16..4: 57.4% 17.5% 25.1%
[libx264 @ 0x7fa93b800c00] mb P  I16..4:  8.0%  8.2%  1.0%  P16..4: 30.5% 11.3%  4.6%  0.0%  0.0%    skip:36.4%
[libx264 @ 0x7fa93b800c00] mb B  I16..4:  0.1%  0.1%  0.0%  B16..8: 34.6%  2.7%  0.2%  direct: 1.3%  skip:60.9%  L0:47.3% L1:49.1% BI: 3.6%
[libx264 @ 0x7fa93b800c00] 8x8 transform intra:42.2% inter:73.3%
[libx264 @ 0x7fa93b800c00] coded y,uvDC,uvAC intra: 26.2% 43.0% 6.8% inter: 5.4% 8.5% 0.1%
[libx264 @ 0x7fa93b800c00] i16 v,h,dc,p: 46% 26%  6% 21%
[libx264 @ 0x7fa93b800c00] i8 v,h,dc,ddl,ddr,vr,hd,vl,hu: 50% 14% 23%  1%  2%  6%  1%  3%  1%
[libx264 @ 0x7fa93b800c00] i4 v,h,dc,ddl,ddr,vr,hd,vl,hu: 40% 32% 10%  3%  3%  4%  2%  5%  2%
[libx264 @ 0x7fa93b800c00] i8c dc,h,v,p: 48% 23% 26%  3%
[libx264 @ 0x7fa93b800c00] Weighted P-Frames: Y:1.2% UV:0.0%
[libx264 @ 0x7fa93b800c00] ref P L0: 71.5% 10.7% 14.8%  2.9%  0.1%
[libx264 @ 0x7fa93b800c00] ref B L0: 95.5%  4.0%  0.5%
[libx264 @ 0x7fa93b800c00] ref B L1: 96.8%  3.2%
[libx264 @ 0x7fa93b800c00] kb/s:285.17

----------- FFProbe source video
/Users/macadmin>ffprobe fileSequence0.ts
ffprobe version 2.5.3 Copyright (c) 2007-2015 the FFmpeg developers
  built on Mar 29 2015 21:31:57 with Apple LLVM version 6.0 (clang-600.0.54) (based on LLVM 3.5svn)
  configuration: --prefix=/usr/local/Cellar/ffmpeg/2.5.3 --enable-shared --enable-pthreads --enable-gpl --enable-version3 --enable-hardcoded-tables --enable-avresample --cc=clang --host-cflags= --host-ldflags= --enable-libx264 --enable-libmp3lame --enable-libvo-aacenc --enable-libxvid --enable-libfreetype --enable-libvorbis --enable-libvpx --enable-libass --enable-ffplay --enable-libfdk-aac --enable-libopus --enable-libquvi --enable-libx265 --enable-nonfree --enable-vda
  libavutil      54. 15.100 / 54. 15.100
  libavcodec     56. 13.100 / 56. 13.100
  libavformat    56. 15.102 / 56. 15.102
  libavdevice    56.  3.100 / 56.  3.100
  libavfilter     5.  2.103 /  5.  2.103
  libavresample   2.  1.  0 /  2.  1.  0
  libswscale      3.  1.101 /  3.  1.101
  libswresample   1.  1.100 /  1.  1.100
  libpostproc    53.  3.100 / 53.  3.100
Input #0, mpegts, from 'fileSequence0.ts':
  Duration: 00:00:09.65, start: 9.952111, bitrate: 412 kb/s
  Program 1 
    Stream #0:0[0x101]: Video: h264 (Constrained Baseline) ([27][0][0][0] / 0x001B), yuv420p, 640x360, 25 fps, 25 tbr, 90k tbn, 50 tbc
    Stream #0:1[0x102]: Audio: aac (LC) ([15][0][0][0] / 0x000F), 44100 Hz, stereo, fltp, 101 kb/s

------ FFPROBE result video
/Users/macadmin>ffprobe output.ts
ffprobe version 2.5.3 Copyright (c) 2007-2015 the FFmpeg developers
  built on Mar 29 2015 21:31:57 with Apple LLVM version 6.0 (clang-600.0.54) (based on LLVM 3.5svn)
  configuration: --prefix=/usr/local/Cellar/ffmpeg/2.5.3 --enable-shared --enable-pthreads --enable-gpl --enable-version3 --enable-hardcoded-tables --enable-avresample --cc=clang --host-cflags= --host-ldflags= --enable-libx264 --enable-libmp3lame --enable-libvo-aacenc --enable-libxvid --enable-libfreetype --enable-libvorbis --enable-libvpx --enable-libass --enable-ffplay --enable-libfdk-aac --enable-libopus --enable-libquvi --enable-libx265 --enable-nonfree --enable-vda
  libavutil      54. 15.100 / 54. 15.100
  libavcodec     56. 13.100 / 56. 13.100
  libavformat    56. 15.102 / 56. 15.102
  libavdevice    56.  3.100 / 56.  3.100
  libavfilter     5.  2.103 /  5.  2.103
  libavresample   2.  1.  0 /  2.  1.  0
  libswscale      3.  1.101 /  3.  1.101
  libswresample   1.  1.100 /  1.  1.100
  libpostproc    53.  3.100 / 53.  3.100
Input #0, mpegts, from 'output.ts':
  Duration: 00:00:09.60, start: 11.400000, bitrate: 334 kb/s
  Program 1 
    Metadata:
      service_name    : Service01
      service_provider: FFmpeg
    Stream #0:0[0x100]: Video: h264 (High) ([27][0][0][0] / 0x001B), yuv420p, 640x360, 25 fps, 25 tbr, 90k tbn, 50 tbc

如何确保输出文件具有相同的 start_time？谢谢。

我决定深入研究一下源代码以了解发生了什么。

• 节目的总体 start_time 是通过使用文件中每个单独流的呈现时间戳 (PTS) 来计算的。

• ffmpeg 设置默认的 Mux 解码延迟值为 0.7 秒。这是在ffmpeg_opt.c中设置的

如果未设置“copyts”标志（在 libavformat/mpegtsenc.c 中），则此延迟值将添加到每个数据包的 PTS 值中：

if (ts->copyts < 1) {
    if (pts != AV_NOPTS_VALUE)
        pts += delay;
    if (dts != AV_NOPTS_VALUE)
        dts += delay;
}

在这种情况下，编码器将延迟值加倍：

const uint64_t delay = 
    av_rescale(s->max_delay, 90000, AV_TIME_BASE)*2;

因此，每个数据包的 PTS 都会额外添加 1.4 秒。如果提供了“copyts”，则会将其添加到输入流中的时间戳值中。

可以使用“muxdelay”标志来覆盖此延迟；在这种情况下，延迟将设置为零。

现在，为什么是 0.7？为什么在 mpeg ts 的情况下两次？我希望我知道答案，大概它在规范中的某个地方。但就目前而言，这是必须要做的。