我有一个提供RTSP流的网络摄像头，我想将其保存到可以说5秒钟的MOV块中。流是：
rtsp://user:pwd@192.168.1.90:10554/tcp/av0_0
我可以打开流并在VLC中播放。我如下运行ffmpeg，看起来很健全，但输出仅为黑色视频。我哪里出错了？
ffmpeg -rtsp_transport tcp -i "rtsp://user:pwd@192.168.1.90:10554/tcp/av0_0" -f segment -segment_time 5 -segment_format mov -c copy -map 0 video%d.mov
ffmpeg version 3.1.1 Copyright (c) 2000-2016 the FFmpeg developers
built with Apple LLVM version 7.3.0 (clang-703.0.31)
configuration: --prefix=/usr/local/Cellar/ffmpeg/3.1.1 --enable-shared --enable-pthreads --enable-gpl --enable-version3 --enable-hardcoded-tables --enable-avresample --cc=clang --host-cflags= --host-ldflags= --enable-opencl --enable-libx264 --enable-libmp3lame --enable-libxvid --enable-ffplay --disable-lzma --enable-vda
libavutil 55. 28.100 / 55. 28.100
libavcodec 57. 48.101 / 57. 48.101
libavformat 57. 41.100 / 57. 41.100
libavdevice 57. 0.101 / 57. 0.101
libavfilter 6. 47.100 / 6. 47.100
libavresample 3. 0. 0 / 3. 0. 0
libswscale 4. 1.100 / 4. 1.100
libswresample 2. 1.100 / 2. 1.100
libpostproc 54. 0.100 / 54. 0.100
Guessed Channel Layout for Input Stream #0.1 : mono
Input #0, rtsp, from 'rtsp://user:pwd@192.168.1.90:10554/tcp/av0_0':
Metadata:
title : streamed by the RTSP server
Duration: N/A, start: 0.230000, bitrate: N/A
Stream #0:0: Video: h264 (High), yuv420p, 1280x720, 20 fps, 25 tbr, 90k tbn, 40 tbc
Stream #0:1: Audio: pcm_alaw, 8000 Hz, 1 channels, s16, 64 kb/s
[segment @ 0x7fda5e012400] Using AVStream.codec to pass codec parameters to muxers is deprecated, use AVStream.codecpar instead.
Last message repeated 1 times
Output #0, segment, to 'video%d.mov':
Metadata:
title : streamed by the RTSP server
encoder : Lavf57.41.100
Stream #0:0: Video: h264, yuv420p, 1280x720, q=2-31, 20 fps, 25 tbr, 10240 tbn, 40 tbc
Stream #0:1: Audio: pcm_alaw, 8000 Hz, mono, 64 kb/s
Stream mapping:
Stream #0:0 -> #0:0 (copy)
Stream #0:1 -> #0:1 (copy)
Press [q] to stop, [?] for help
[segment @ 0x7fda5e012400] Non-monotonous DTS in output stream 0:0; previous: 0, current: -1946; changing to 1. This may result in incorrect timestamps in the output file.
[segment @ 0x7fda5e012400] Non-monotonous DTS in output stream 0:0; previous: 1, current: -1536; changing to 2. This may result in incorrect timestamps in the output file.
[segment @ 0x7fda5e012400] Non-monotonous DTS in output stream 0:0; previous: 2, current: -1126; changing to 3. This may result in incorrect timestamps in the output file.
[segment @ 0x7fda5e012400] Non-monotonous DTS in output stream 0:0; previous: 3, current: -717; changing to 4. This may result in incorrect timestamps in the output file.
[segment @ 0x7fda5e012400] Non-monotonous DTS in output stream 0:0; previous: 4, current: -307; changing to 5. This may result in incorrect timestamps in the output file.
frame= 204 fps= 24 q=-1.0 Lsize=N/A time=00:00:07.89 bitrate=N/A speed=0.937x
video:2057kB audio:0kB subtitle:0kB other streams:0kB global headers:0kB muxing overhead: unknown
Exiting normally, received signal 2.