如果有一天不知道為甚麼你需要透過 Linux / Raspberry Pi 串流 HDMI capture card 到網絡上另一個位置的話，你可以用這個 ffmpeg command：

ffmpeg -f v4l2 \
    -input_format mjpeg \
    -video_size 1920x1080 \
    -framerate 25 \
    -i /dev/video0 \
    -vcodec mpeg4 \
    -pix_fmt yuv420p \
    -q:v 1 \
    -f mpegts \
    -flush_packets 1 \
    -max_delay 0\
    -analyzeduration 10 \
    -probesize 32 \
    -fflags nobuffer \
    -tune zerolatency \
    -listen 1 \
    

如果你的電腦上並沒有 v4l2，可以透過以下指令安裝並抓到 capture card 支援的輸出格式

sudo apt-get install v4l-utils
v4l2-ctl --device=/dev/video0 --all

輸出例子：

Driver Info:
        Driver name      : uvcvideo
        Card type        : usb video: usb video
        Bus info         : usb-0000:00:14.0-2
        Driver version   : 6.1.119
        Capabilities     : 0x84a00001
                Video Capture
                Metadata Capture
                Streaming
                Extended Pix Format
                Device Capabilities
        Device Caps      : 0x04200001
                Video Capture
                Streaming
                Extended Pix Format
Media Driver Info:
        Driver name      : uvcvideo
        Model            : usb video: usb video
        Serial           :
        Bus info         : usb-0000:00:14.0-2
        Media version    : 6.1.119
        Hardware revision: 0x00002100 (8448)
        Driver version   : 6.1.119
Interface Info:
        ID               : 0x03000002
        Type             : V4L Video
Entity Info:
        ID               : 0x00000001 (1)
        Name             : usb video: usb video
        Function         : V4L2 I/O
        Flags            : default
        Pad 0x01000007   : 0: Sink
          Link 0x0200000d: from remote pad 0x100000a of entity 'Processing 2' (Video Pixel Formatter):                            Data, Enabled, Immutable
Priority: 2
Video input : 0 (Input 1: ok)
Format Video Capture:
        Width/Height      : 1920/1080
        Pixel Format      : 'MJPG' (Motion-JPEG)
        Field             : None
        Bytes per Line    : 0
        Size Image        : 4147200
        Colorspace        : sRGB
        Transfer Function : Rec. 709
        YCbCr/HSV Encoding: ITU-R 601
        Quantization      : Default (maps to Full Range)
        Flags             :
Crop Capability Video Capture:
        Bounds      : Left 0, Top 0, Width 1920, Height 1080
        Default     : Left 0, Top 0, Width 1920, Height 1080
        Pixel Aspect: 1/1
Selection Video Capture: crop_default, Left 0, Top 0, Width 1920, Height 1080, Flags:
Selection Video Capture: crop_bounds, Left 0, Top 0, Width 1920, Height 1080, Flags:
Streaming Parameters Video Capture:
        Capabilities     : timeperframe
        Frames per second: 30.000 (30/1)
        Read buffers     : 0

User Controls

                     brightness 0x00980900 (int)    : min=-128 max=127 step=1 default=-11 value=-11
                       contrast 0x00980901 (int)    : min=0 max=255 step=1 default=148 value=148
                     saturation 0x00980902 (int)    : min=0 max=255 step=1 default=180 value=180
                            hue 0x00980903 (int)    : min=-128 max=127 step=1 default=0 value=0

另外如果要看到完整支援的 resolution 跟 framerate 的話可以用這個 command

v4l2-ctl -D -d /dev/video0 --list-formats-ext

它會輸出很多不同的支援格式，例如說這是 UYVY422，支援例如 480×270 然後一列 fps 等等，ffmpeg 的指令也可以按支援的格式來調整。

       Index       : 1
        Type        : Video Capture
        Pixel Format: 'UYVY'
        Name        : UYVY 4:2:2
                Size: Discrete 424x240
                        Interval: Discrete 0.011s (90.000 fps)
                        Interval: Discrete 0.017s (60.000 fps)
                        Interval: Discrete 0.033s (30.000 fps)
                        Interval: Discrete 0.067s (15.000 fps)
                        Interval: Discrete 0.167s (6.000 fps)
                Size: Discrete 480x270
                        Interval: Discrete 0.011s (90.000 fps)
                        Interval: Discrete 0.017s (60.000 fps)
                        Interval: Discrete 0.033s (30.000 fps)
                        Interval: Discrete 0.067s (15.000 fps)
                        Interval: Discrete 0.167s (6.000 fps)
                Size: Discrete 640x360
                        Interval: Discrete 0.011s (90.000 fps)
                        Interval: Discrete 0.017s (60.000 fps)
                        Interval: Discrete 0.033s (30.000 fps)
                        Interval: Discrete 0.067s (15.000 fps)
                        Interval: Discrete 0.167s (6.000 fps)

連接到串流

要連接的話可以用 VLC 或是 OBS 來觀看，以 VLC 為例：

然後在網址列輸入伺服器 / 電腦的 IP 地址即可。