salvando vídeo compatível com padrão das câmeras Hikvision DS-2CD2032

Question

Estou tentando salvar o vídeo de câmeras Hikvision DS-2CD2032 ( aka Swann HD-820CAM também conhecido como Lorex MCNB2151) via ffmpeg. Basicamente funciona com um comando como este:

$ ffmpeg -rtsp_transport tcp -i rtsp://user:pass@ip/ -c copy -map 0:0 driveway.mp4
ffmpeg version N-73641-gb90b6af Copyright (c) 2000-2015 the FFmpeg developers
  built with gcc 4.9.1 (Ubuntu 4.9.1-16ubuntu6)
  configuration:
  libavutil      54. 28.100 / 54. 28.100
  libavcodec     56. 48.100 / 56. 48.100
  libavformat    56. 40.100 / 56. 40.100
  libavdevice    56.  4.100 / 56.  4.100
  libavfilter     5. 21.100 /  5. 21.100
  libswscale      3.  1.101 /  3.  1.101
  libswresample   1.  2.100 /  1.  2.100
Input #0, rtsp, from 'rtsp://user:pass@ip/':
  Metadata:
    title           : Media Presentation
  Duration: N/A, start: 0.466078, bitrate: N/A
    Stream #0:0: Video: h264 (Main), yuv420p(tv, bt709), 1280x720, 15 fps, 15 tbr, 90k tbn, 30 tbc
    Stream #0:1: Data: none
[mp4 @ 0x24f6720] Codec for stream 0 does not use global headers but container format requires global headers
Output #0, mp4, to 'driveway.mp4':
  Metadata:
    title           : Media Presentation
    encoder         : Lavf56.40.100
    Stream #0:0: Video: h264 ([33][0][0][0] / 0x0021), yuv420p, 1280x720, q=2-31, 15 fps, 15 tbr, 90k tbn, 90k tbc
Stream mapping:
  Stream #0:0 -> #0:0 (copy)
Press [q] to stop, [?] for help
[mp4 @ 0x24f6720] Non-monotonous DTS in output stream 0:0; previous: 0, current: -30013; changing to 1. This may result in incorrect timestamps in the output file.
[mp4 @ 0x24f6720] Non-monotonous DTS in output stream 0:0; previous: 1, current: -23990; changing to 2. This may result in incorrect timestamps in the output file.
[mp4 @ 0x24f6720] Non-monotonous DTS in output stream 0:0; previous: 2, current: -17996; changing to 3. This may result in incorrect timestamps in the output file.
[mp4 @ 0x24f6720] Non-monotonous DTS in output stream 0:0; previous: 3, current: -11994; changing to 4. This may result in incorrect timestamps in the output file.
[mp4 @ 0x24f6720] Non-monotonous DTS in output stream 0:0; previous: 4, current: -5992; changing to 5. This may result in incorrect timestamps in the output file.
[mp4 @ 0x24f6720] Non-monotonous DTS in output stream 0:0; previous: 5, current: -18; changing to 6. This may result in incorrect timestamps in the output file.
frame=  178 fps= 18 q=-1.0 Lsize=    1711kB time=00:00:11.39 bitrate=1229.3kbits/s
video:1708kB audio:0kB subtitle:0kB other streams:0kB global headers:0kB muxing overhead: 0.177573%

mas estou preocupado com as mensagens de aviso. Em particular, quero abordar qualquer problema que possa fazer com que o vídeo não seja reproduzido sem problemas ou que não interaja bem com alguns jogadores. Então ...

1. O que são "cabeçalhos globais"? Quais são as consequências deles estarem ausentes? Eu encontrei uma nota sobre dump_extra na documentação do ffmpeg bitstream filters . Se eu adicionar o "-flags: v + global_header -bsf: v dump_extra", descreve, o aviso desaparece. O que está fazendo exatamente? Eu entendo que move algo de um cabeçalho por pacote para um cabeçalho global? Como eu iria examinar estes / observar a diferença?
2. O que posso fazer sobre os avisos "Non-monotonous DTS"?

fwiw, eu escrevi um programa personalizado com libavformat que despejou as informações do DTS de cada frame da seguinte forma:

while (av_read_frame(input_context, &packet) == 0) {
  if (packet.flags & AV_PKT_FLAG_KEY) {
    cout << "have key frame, dts: " << packet.dts << endl;
  } else {
    cout << "  have non-key frame, dts: " << packet.dts << endl;
  }
}

e ele cuspiu isso, então eu acho que são apenas os quadros-chave que têm os dts incorretos? Não sei o que fazer com isso.

have key frame, dts: 41995
  have non-key frame, dts: 12033
  have non-key frame, dts: 17966
have key frame, dts: 23970
  have non-key frame, dts: 29992
  have non-key frame, dts: 35992
  have non-key frame, dts: 41995
  have non-key frame, dts: 47995
have key frame, dts: 53973
  have non-key frame, dts: 59994
  have non-key frame, dts: 65996
  have non-key frame, dts: 71995
  have non-key frame, dts: 77994
have key frame, dts: 83978
  have non-key frame, dts: 89993
  have non-key frame, dts: 95997
  have non-key frame, dts: 102035
  have non-key frame, dts: 107978
have key frame, dts: 113976
  have non-key frame, dts: 119998
  have non-key frame, dts: 126000
  have non-key frame, dts: 131997
  have non-key frame, dts: 138000