我正在将树莓派相机中的数据传输到ffmpeg，以将其转换为mp4流。我不是使用libavformat / libavformat这样做，而是直接像这样调用"dev": "NODE_ENV=development VERSION=$(git describe --tag) concurrently \"npm run server\" \"npm run client\""
：
ffmpeg这是我围绕fork和exec的包装，如下所示：
context->ffmpeg_process = utils::launch_subprocess(
"ffmpeg",{"-f","rawvideo","-pix_fmt","yuv420p","-s","1920x1080","-r","30","-i","-","-c","libx264","-f","mp4","-movflags","frag_keyframe+empty_moov","-loglevel","trace"}
);
现在我有一个由树莓派相机调用的回调：
const auto child = fork();
if(child == 0) {
if (dup2(stdin_pipe[PIPE_READ],STDIN_FILENO) == -1) {
exit(errno);
}
// same for stdout and sterr
execvp(command.c_str(),proc_args);
exit(errno);
} else if(child > 0) {
// same for stdout and stderr
ret_process.stdin_pipe = stdin_pipe[PIPE_WRITE];
}
我故意将每个帧追加到文件，因为我正在运行与上述完全相同的命令（使用 void CameraHandler::handle_camera_frame(const std::vector<uint8_t> &data,std::size_t size) {
FILE* f = fopen("output.yuv4","ab");
fwrite(data.data(),1,size,f);
fclose(f);
std::lock_guard<std::mutex> l{_listener_lock};
for (const auto &listener : _data_listeners) {
std::size_t written = 0;
while (written < size) {
const auto num_written = write(listener->ffmpeg_process.stdin_pipe,data.data() + written,size - written);
written += num_written;
if(num_written < 0) {
log->error("Broken stdin pipe");
break;
}
}
}
}
进行交叉检查）。
现在，我可以看到我正在从相机读取一些数据，并将其推送到ffmpeg进程。但是在第一次读取ffmpeg后已经抱怨输入数据无效：
cat output.yuv4 | ffmpeg ... > output4.mp4我现在很困惑。从字面上看，这与我[2019-11-06 20:08:04.010] [11872:11932] [carpi::data::CameraHandler] [info] Launched ffmpeg process. PID: 11933,error: 0
[2019-11-06 20:08:04.014] [11872:11932] [carpi::video::RawCameraStream] [info] Camera dimension: 1920/1080
ffmpeg version 4.1.4-1+rpt1~deb10u1 Copyright (c) 2000-2019 the FFmpeg developers
built with gcc 8 (Raspbian 8.3.0-6+rpi1)
configuration: --prefix=/usr --extra-version='1+rpt1~deb10u1' --toolchain=hardened --libdir=/usr/lib/arm-linux-gnueabihf --incdir=/usr/include/arm-linux-gnueabihf --arch=arm --enable-gpl --disable-stripping --enable-avresample --disable-filter=resample --enable-avisynth --enable-gnutls --enable-ladspa --enable-libaom --enable-libass --enable-libbluray --enable-libbs2b --enable-libcaca --enable-libcdio --enable-libcodec2 --enable-libflite --enable-libfontconfig --enable-libfreetype --enable-libfribidi --enable-libgme --enable-libgsm --enable-libjack --enable-libmp3lame --enable-libmysofa --enable-libopenjpeg --enable-libopenmpt --enable-libopus --enable-libpulse --enable-librsvg --enable-librubberband --enable-libshine --enable-libsnappy --enable-libsoxr --enable-libspeex --enable-libssh --enable-libtheora --enable-libtwolame --enable-libvidstab --enable-libvorbis --enable-libvpx --enable-libwavpack --enable-libwebp --enable-libx265 --enable-libxml2 --enable-libxvid --enable-libzmq --enable-libzvbi --enable-lv2 --enable-omx --enable-openal --enable-opengl --enable-sdl2 --enable-omx-rpi --enable-mmal --enable-libdc1394 --enable-libdrm --enable-libiec61883 --enable-chromaprint --enable-frei0r --enable-libx264 --enable-shared
libavutil 56. 22.100 / 56. 22.100
libavcodec 58. 35.100 / 58. 35.100
libavformat 58. 20.100 / 58. 20.100
libavdevice 58. 5.100 / 58. 5.100
libavfilter 7. 40.101 / 7. 40.101
libavresample 4. 0. 0 / 4. 0. 0
libswscale 5. 3.100 / 5. 3.100
libswresample 3. 3.100 / 3. 3.100
libpostproc 55. 3.100 / 55. 3.100
Successfully parsed a group of options.
Parsing a group of options: input url -.
Applying option pix_fmt (set pixel format) with argument yuv420p.
Applying option s (set frame size (WxH or abbreviation)) with argument 1920x1080.
Applying option r (set frame rate (Hz value,fraction or abbreviation)) with argument 30.
Successfully parsed a group of options.
Opening an input file: -.
[NULL @ 0xcd02d0] Opening 'pipe:' for reading
[pipe @ 0xcd0b50] Setting default whitelist 'crypto'
[AVIOContext @ 0xcd8d50] Statistics: 1048576 bytes read,0 seeks
pipe:: Invalid data found when processing input
正在从文件中进行管道传输相同。我的fwrite有什么问题吗？