ffmpeg - 需要帮助配置 FFMPEG 以使用网络摄像头 h264 流
问题描述
我一直在尝试从 H264 USB 网络摄像头获取 H264 流，但我没有取得太大进展，所以我希望有人比我更了解 FFMPEG！
SO上有几十个问题/答案，但没有一个能解决我的问题。
简而言之，我得到了一个非常像素化（或有时大部分是绿色）的屏幕。我正在使用 VLC 来测试来自 RTSP 服务器的流。我正在使用 FFMPEG 将网络摄像头流复制到本地 RTSP 服务器。
网络摄像头还支持我可以开始工作的 YUYV - 它只是 h264 流给我带来了问题。
所以这就是设备的呈现方式：
H264 USB Camera: USB Camera (usb-20980000.usb-1):
/dev/video0
/dev/video1
/dev/video2
/dev/video3
/dev/video0 是 YUYV 和 MPEG 流 /dev/video2 是具有以下功能的 h264 流：
ioctl: VIDIOC_ENUM_FMT
Type: Video Capture
[0]: 'H264' (H.264, compressed)
Size: Discrete 1920x1080
Interval: Discrete 0.033s (30.000 fps)
Interval: Discrete 0.040s (25.000 fps)
Interval: Discrete 0.067s (15.000 fps)
Interval: Discrete 0.033s (30.000 fps)
Interval: Discrete 0.040s (25.000 fps)
Interval: Discrete 0.067s (15.000 fps)
Size: Discrete 1280x720
Interval: Discrete 0.033s (30.000 fps)
Interval: Discrete 0.040s (25.000 fps)
Interval: Discrete 0.067s (15.000 fps)
Size: Discrete 800x600
Interval: Discrete 0.033s (30.000 fps)
Interval: Discrete 0.040s (25.000 fps)
Interval: Discrete 0.067s (15.000 fps)
Size: Discrete 640x480
Interval: Discrete 0.033s (30.000 fps)
Interval: Discrete 0.040s (25.000 fps)
Interval: Discrete 0.067s (15.000 fps)
Size: Discrete 640x360
Interval: Discrete 0.033s (30.000 fps)
Interval: Discrete 0.040s (25.000 fps)
Interval: Discrete 0.067s (15.000 fps)
Size: Discrete 352x288
Interval: Discrete 0.033s (30.000 fps)
Interval: Discrete 0.040s (25.000 fps)
Interval: Discrete 0.067s (15.000 fps)
Size: Discrete 320x240
Interval: Discrete 0.033s (30.000 fps)
Interval: Discrete 0.040s (25.000 fps)
Interval: Discrete 0.067s (15.000 fps)
Size: Discrete 1920x1080
Interval: Discrete 0.033s (30.000 fps)
Interval: Discrete 0.040s (25.000 fps)
Interval: Discrete 0.067s (15.000 fps)
Interval: Discrete 0.033s (30.000 fps)
Interval: Discrete 0.040s (25.000 fps)
Interval: Discrete 0.067s (15.000 fps)
我已经尝试了各种分辨率，较小的分辨率会稍微减少像素化图像，但没有一个是可用的，并且绝对不能与 YUYV 高分辨率结果相比。
这个（YUYV）命令有效：
ffmpeg -input_format yuyv422 -f video4linux2 -s 1280x720 -r 10 -i /dev/video0 -c:v h264_omx -r 10 -b:v 2M -an -f rtsp rtsp://localhost:80/live/stream
这两个 h264 选项不起作用：
ffmpeg -input_format h264 -f video4linux2 -video_size 1920x1080 -framerate 30 -i /dev/video0 -c:v copy -an -f rtsp rtsp://localhost:80/live/stream
ffmpeg -re -i /dev/video2 -video_size 800x600 -framerate 15 -pix_fmt yuv420p -tune zerolatency -c:v copy -an -f rtsp rtsp://localhost:80/live/stream
对于最后一个命令，FFMPEG 输出如下所示：
ffmpeg version git-2020-08-07-6fdf3cc Copyright (c) 2000-2020 the FFmpeg developers
built with gcc 8 (Raspbian 8.3.0-6+rpi1)
configuration: --extra-ldflags=-latomic --arch=armel --target-os=linux --enable-gpl --enable-omx --enable-omx-rpi --enable-nonfree --enable-libfreetype --enable-libx264 --enable-libmp3lame --enable-mmal --enable-indev=alsa --enable-outdev=alsa
libavutil 56. 58.100 / 56. 58.100
libavcodec 58.100.100 / 58.100.100
libavformat 58. 50.100 / 58. 50.100
libavdevice 58. 11.101 / 58. 11.101
libavfilter 7. 87.100 / 7. 87.100
libswscale 5. 8.100 / 5. 8.100
libswresample 3. 8.100 / 3. 8.100
libpostproc 55. 8.100 / 55. 8.100
Input #0, video4linux2,v4l2, from '/dev/video2':
Duration: N/A, start: 1353.265049, bitrate: N/A
Stream #0:0: Video: h264 (Main), yuv420p(progressive), 1920x1080, 30 fps, 30 tbr, 1000k tbn, 2000k tbc
[udp @ 0x38c29f0] attempted to set receive buffer to size 393216 but it only ended up set as 360448
[udp @ 0x38d7b50] attempted to set receive buffer to size 393216 but it only ended up set as 360448
Output #0, rtsp, to 'rtsp://localhost:80/live/stream':
Metadata:
encoder : Lavf58.50.100
Stream #0:0: Video: h264 (Main), yuv420p(progressive), 1920x1080, q=2-31, 30 fps, 30 tbr, 90k tbn, 1000k tbc
Stream mapping:
Stream #0:0 -> #0:0 (copy)
Press [q] to stop, [?] for help
[rtsp @ 0x38fd890] Timestamps are unset in a packet for stream 0. This is deprecated and will stop working in the future. Fix your code to set the timestamps properly
[rtsp @ 0x38fd890] Non-monotonous DTS in output stream 0:0; previous: 0, current: 0; changing to 1. This may result in incorrect timestamps in the output file.
frame= 348 fps= 18 q=-1.0 size=N/A time=00:00:21.03 bitrate=N/A speed=1.09x
这个问题看起来与带宽相关或正在使用的设备缺乏处理能力但是YUYV 以高分辨率工作并且（采用完全不同的方法，即不使用 FFMPEG）我可以得到一个非常体面的 MPEG 流在相同的设备。
那么有任何 FFMPEG 专家可以帮助我获得正确的 h264 流参数吗？