如何在ffmpeg中捕捉stdoutstream,然后将其pipe理到v4l2loopback

我试图将我的h264streampipe道ffmpeg,然后到我的v4l2loopback设备。 问题是我对于linux相当新,所以只是不能得到它的工作。 该stream可以输出到标准输出,但我不知道如何用ffmpeg再次捕捉它,然后再将其输送到我的v4l2loopback设备。

有人知道如何做到这一点,或者可能是如何解决这个问题的指针?

这是捕捉程序:

PS! 您几乎可以在代码的底部find捕获程序的选项。

/* * V4L2 video capture example, modified by Derek Molloy for the Logitech C920 camera * Modifications, added the -F mode for H264 capture and associated help detail * www.derekmolloy.ie * * V4L2 video capture example * * This program can be used and distributed without restrictions. * * This program is provided with the V4L2 API * see http://linuxtv.org/docs.php for more information */ #include <stdio.h> #include <stdlib.h> #include <string.h> #include <assert.h> #include <getopt.h> /* getopt_long() */ #include <fcntl.h> /* low-level i/o */ #include <unistd.h> #include <errno.h> #include <sys/stat.h> #include <sys/types.h> #include <sys/time.h> #include <sys/mman.h> #include <sys/ioctl.h> #include <linux/videodev2.h> #define CLEAR(x) memset(&(x), 0, sizeof(x)) enum io_method { IO_METHOD_READ, IO_METHOD_MMAP, IO_METHOD_USERPTR, }; struct buffer { void *start; size_t length; }; static char *dev_name; static enum io_method io = IO_METHOD_MMAP; static int fd = -1; struct buffer *buffers; static unsigned int n_buffers; static int out_buf; static int force_format = 0; static int frame_count = 100; static void errno_exit(const char *s) { fprintf(stderr, "%s error %d, %s\n", s, errno, strerror(errno)); exit(EXIT_FAILURE); } static int xioctl(int fh, int request, void *arg) { int r; do { r = ioctl(fh, request, arg); } while (-1 == r && EINTR == errno); return r; } static void process_image(const void *p, int size) { if (out_buf) fwrite(p, size, 1, stdout); fflush(stderr); fprintf(stderr, "."); fflush(stdout); } static int read_frame(void) { struct v4l2_buffer buf; unsigned int i; switch (io) { case IO_METHOD_READ: if (-1 == read(fd, buffers[0].start, buffers[0].length)) { switch (errno) { case EAGAIN: return 0; case EIO: /* Could ignore EIO, see spec. */ /* fall through */ default: errno_exit("read"); } } process_image(buffers[0].start, buffers[0].length); break; case IO_METHOD_MMAP: CLEAR(buf); buf.type = V4L2_BUF_TYPE_VIDEO_CAPTURE; buf.memory = V4L2_MEMORY_MMAP; if (-1 == xioctl(fd, VIDIOC_DQBUF, &buf)) { switch (errno) { case EAGAIN: return 0; case EIO: /* Could ignore EIO, see spec. */ /* fall through */ default: errno_exit("VIDIOC_DQBUF"); } } assert(buf.index < n_buffers); process_image(buffers[buf.index].start, buf.bytesused); if (-1 == xioctl(fd, VIDIOC_QBUF, &buf)) errno_exit("VIDIOC_QBUF"); break; case IO_METHOD_USERPTR: CLEAR(buf); buf.type = V4L2_BUF_TYPE_VIDEO_CAPTURE; buf.memory = V4L2_MEMORY_USERPTR; if (-1 == xioctl(fd, VIDIOC_DQBUF, &buf)) { switch (errno) { case EAGAIN: return 0; case EIO: /* Could ignore EIO, see spec. */ /* fall through */ default: errno_exit("VIDIOC_DQBUF"); } } for (i = 0; i < n_buffers; ++i) if (buf.m.userptr == (unsigned long)buffers[i].start && buf.length == buffers[i].length) break; assert(i < n_buffers); process_image((void *)buf.m.userptr, buf.bytesused); if (-1 == xioctl(fd, VIDIOC_QBUF, &buf)) errno_exit("VIDIOC_QBUF"); break; } return 1; } static void mainloop(void) { unsigned int count; unsigned int loopIsInfinite = 0; if (frame_count == 0) loopIsInfinite = 1; //infinite loop count = frame_count; while ((count-- > 0) || loopIsInfinite) { for (;;) { fd_set fds; struct timeval tv; int r; FD_ZERO(&fds); FD_SET(fd, &fds); /* Timeout. */ tv.tv_sec = 2; tv.tv_usec = 0; r = select(fd + 1, &fds, NULL, NULL, &tv); if (-1 == r) { if (EINTR == errno) continue; errno_exit("select"); } if (0 == r) { fprintf(stderr, "select timeout\n"); exit(EXIT_FAILURE); } if (read_frame()) break; /* EAGAIN - continue select loop. */ } } } static void stop_capturing(void) { enum v4l2_buf_type type; switch (io) { case IO_METHOD_READ: /* Nothing to do. */ break; case IO_METHOD_MMAP: case IO_METHOD_USERPTR: type = V4L2_BUF_TYPE_VIDEO_CAPTURE; if (-1 == xioctl(fd, VIDIOC_STREAMOFF, &type)) errno_exit("VIDIOC_STREAMOFF"); break; } } static void start_capturing(void) { unsigned int i; enum v4l2_buf_type type; switch (io) { case IO_METHOD_READ: /* Nothing to do. */ break; case IO_METHOD_MMAP: for (i = 0; i < n_buffers; ++i) { struct v4l2_buffer buf; CLEAR(buf); buf.type = V4L2_BUF_TYPE_VIDEO_CAPTURE; buf.memory = V4L2_MEMORY_MMAP; buf.index = i; if (-1 == xioctl(fd, VIDIOC_QBUF, &buf)) errno_exit("VIDIOC_QBUF"); } type = V4L2_BUF_TYPE_VIDEO_CAPTURE; if (-1 == xioctl(fd, VIDIOC_STREAMON, &type)) errno_exit("VIDIOC_STREAMON"); break; case IO_METHOD_USERPTR: for (i = 0; i < n_buffers; ++i) { struct v4l2_buffer buf; CLEAR(buf); buf.type = V4L2_BUF_TYPE_VIDEO_CAPTURE; buf.memory = V4L2_MEMORY_USERPTR; buf.index = i; buf.m.userptr = (unsigned long)buffers[i].start; buf.length = buffers[i].length; if (-1 == xioctl(fd, VIDIOC_QBUF, &buf)) errno_exit("VIDIOC_QBUF"); } type = V4L2_BUF_TYPE_VIDEO_CAPTURE; if (-1 == xioctl(fd, VIDIOC_STREAMON, &type)) errno_exit("VIDIOC_STREAMON"); break; } } static void uninit_device(void) { unsigned int i; switch (io) { case IO_METHOD_READ: free(buffers[0].start); break; case IO_METHOD_MMAP: for (i = 0; i < n_buffers; ++i) if (-1 == munmap(buffers[i].start, buffers[i].length)) errno_exit("munmap"); break; case IO_METHOD_USERPTR: for (i = 0; i < n_buffers; ++i) free(buffers[i].start); break; } free(buffers); } static void init_read(unsigned int buffer_size) { buffers = calloc(1, sizeof(*buffers)); if (!buffers) { fprintf(stderr, "Out of memory\n"); exit(EXIT_FAILURE); } buffers[0].length = buffer_size; buffers[0].start = malloc(buffer_size); if (!buffers[0].start) { fprintf(stderr, "Out of memory\n"); exit(EXIT_FAILURE); } } static void init_mmap(void) { struct v4l2_requestbuffers req; CLEAR(req); req.count = 4; req.type = V4L2_BUF_TYPE_VIDEO_CAPTURE; req.memory = V4L2_MEMORY_MMAP; if (-1 == xioctl(fd, VIDIOC_REQBUFS, &req)) { if (EINVAL == errno) { fprintf(stderr, "%s does not support " "memory mapping\n", dev_name); exit(EXIT_FAILURE); } else { errno_exit("VIDIOC_REQBUFS"); } } if (req.count < 2) { fprintf(stderr, "Insufficient buffer memory on %s\n", dev_name); exit(EXIT_FAILURE); } buffers = calloc(req.count, sizeof(*buffers)); if (!buffers) { fprintf(stderr, "Out of memory\n"); exit(EXIT_FAILURE); } for (n_buffers = 0; n_buffers < req.count; ++n_buffers) { struct v4l2_buffer buf; CLEAR(buf); buf.type = V4L2_BUF_TYPE_VIDEO_CAPTURE; buf.memory = V4L2_MEMORY_MMAP; buf.index = n_buffers; if (-1 == xioctl(fd, VIDIOC_QUERYBUF, &buf)) errno_exit("VIDIOC_QUERYBUF"); buffers[n_buffers].length = buf.length; buffers[n_buffers].start = mmap(NULL /* start anywhere */, buf.length, PROT_READ | PROT_WRITE /* required */, MAP_SHARED /* recommended */, fd, buf.m.offset); if (MAP_FAILED == buffers[n_buffers].start) errno_exit("mmap"); } } static void init_userp(unsigned int buffer_size) { struct v4l2_requestbuffers req; CLEAR(req); req.count = 4; req.type = V4L2_BUF_TYPE_VIDEO_CAPTURE; req.memory = V4L2_MEMORY_USERPTR; if (-1 == xioctl(fd, VIDIOC_REQBUFS, &req)) { if (EINVAL == errno) { fprintf(stderr, "%s does not support " "user pointer i/o\n", dev_name); exit(EXIT_FAILURE); } else { errno_exit("VIDIOC_REQBUFS"); } } buffers = calloc(4, sizeof(*buffers)); if (!buffers) { fprintf(stderr, "Out of memory\n"); exit(EXIT_FAILURE); } for (n_buffers = 0; n_buffers < 4; ++n_buffers) { buffers[n_buffers].length = buffer_size; buffers[n_buffers].start = malloc(buffer_size); if (!buffers[n_buffers].start) { fprintf(stderr, "Out of memory\n"); exit(EXIT_FAILURE); } } } static void init_device(void) { struct v4l2_capability cap; struct v4l2_cropcap cropcap; struct v4l2_crop crop; struct v4l2_format fmt; unsigned int min; if (-1 == xioctl(fd, VIDIOC_QUERYCAP, &cap)) { if (EINVAL == errno) { fprintf(stderr, "%s is no V4L2 device\n", dev_name); exit(EXIT_FAILURE); } else { errno_exit("VIDIOC_QUERYCAP"); } } if (!(cap.capabilities & V4L2_CAP_VIDEO_CAPTURE)) { fprintf(stderr, "%s is no video capture device\n", dev_name); exit(EXIT_FAILURE); } switch (io) { case IO_METHOD_READ: if (!(cap.capabilities & V4L2_CAP_READWRITE)) { fprintf(stderr, "%s does not support read i/o\n", dev_name); exit(EXIT_FAILURE); } break; case IO_METHOD_MMAP: case IO_METHOD_USERPTR: if (!(cap.capabilities & V4L2_CAP_STREAMING)) { fprintf(stderr, "%s does not support streaming i/o\n", dev_name); exit(EXIT_FAILURE); } break; } /* Select video input, video standard and tune here. */ CLEAR(cropcap); cropcap.type = V4L2_BUF_TYPE_VIDEO_CAPTURE; if (0 == xioctl(fd, VIDIOC_CROPCAP, &cropcap)) { crop.type = V4L2_BUF_TYPE_VIDEO_CAPTURE; crop.c = cropcap.defrect; /* reset to default */ if (-1 == xioctl(fd, VIDIOC_S_CROP, &crop)) { switch (errno) { case EINVAL: /* Cropping not supported. */ break; default: /* Errors ignored. */ break; } } } else { /* Errors ignored. */ } CLEAR(fmt); fmt.type = V4L2_BUF_TYPE_VIDEO_CAPTURE; fprintf(stderr, "Force Format %d\n", force_format); if (force_format) { if (force_format==2){ fmt.fmt.pix.width = 1920; fmt.fmt.pix.height = 1080; fmt.fmt.pix.pixelformat = V4L2_PIX_FMT_H264; fmt.fmt.pix.field = V4L2_FIELD_INTERLACED; } else if(force_format==1){ fmt.fmt.pix.width = 640; fmt.fmt.pix.height = 480; fmt.fmt.pix.pixelformat = V4L2_PIX_FMT_YUYV; fmt.fmt.pix.field = V4L2_FIELD_INTERLACED; } if (-1 == xioctl(fd, VIDIOC_S_FMT, &fmt)) errno_exit("VIDIOC_S_FMT"); /* Note VIDIOC_S_FMT may change width and height. */ } else { /* Preserve original settings as set by v4l2-ctl for example */ if (-1 == xioctl(fd, VIDIOC_G_FMT, &fmt)) errno_exit("VIDIOC_G_FMT"); } /* Buggy driver paranoia. */ min = fmt.fmt.pix.width * 2; if (fmt.fmt.pix.bytesperline < min) fmt.fmt.pix.bytesperline = min; min = fmt.fmt.pix.bytesperline * fmt.fmt.pix.height; if (fmt.fmt.pix.sizeimage < min) fmt.fmt.pix.sizeimage = min; switch (io) { case IO_METHOD_READ: init_read(fmt.fmt.pix.sizeimage); break; case IO_METHOD_MMAP: init_mmap(); break; case IO_METHOD_USERPTR: init_userp(fmt.fmt.pix.sizeimage); break; } } static void close_device(void) { if (-1 == close(fd)) errno_exit("close"); fd = -1; } static void open_device(void) { struct stat st; if (-1 == stat(dev_name, &st)) { fprintf(stderr, "Cannot identify '%s': %d, %s\n", dev_name, errno, strerror(errno)); exit(EXIT_FAILURE); } if (!S_ISCHR(st.st_mode)) { fprintf(stderr, "%s is no device\n", dev_name); exit(EXIT_FAILURE); } fd = open(dev_name, O_RDWR /* required */ | O_NONBLOCK, 0); if (-1 == fd) { fprintf(stderr, "Cannot open '%s': %d, %s\n", dev_name, errno, strerror(errno)); exit(EXIT_FAILURE); } } static void usage(FILE *fp, int argc, char **argv) { fprintf(fp, "Usage: %s [options]\n\n" "Version 1.3\n" "Options:\n" "-d | --device name Video device name [%s]\n" "-h | --help Print this message\n" "-m | --mmap Use memory mapped buffers [default]\n" "-r | --read Use read() calls\n" "-u | --userp Use application allocated buffers\n" "-o | --output Outputs stream to stdout\n" "-f | --format Force format to 640x480 YUYV\n" "-F | --formatH264 Force format to 1920x1080 H264\n" "-c | --count Number of frames to grab [%i] - use 0 for infinite\n" "\n" "Example usage: capture -F -o -c 300 > output.raw\n" "Captures 300 frames of H264 at 1920x1080 - use raw2mpg4 script to convert to mpg4\n", argv[0], dev_name, frame_count); } static const char short_options[] = "d:hmruofFc:"; static const struct option long_options[] = { { "device", required_argument, NULL, 'd' }, { "help", no_argument, NULL, 'h' }, { "mmap", no_argument, NULL, 'm' }, { "read", no_argument, NULL, 'r' }, { "userp", no_argument, NULL, 'u' }, { "output", no_argument, NULL, 'o' }, { "format", no_argument, NULL, 'f' }, { "formatH264", no_argument, NULL, 'F' }, { "count", required_argument, NULL, 'c' }, { 0, 0, 0, 0 } }; int main(int argc, char **argv) { dev_name = "/dev/video0"; for (;;) { int idx; int c; c = getopt_long(argc, argv, short_options, long_options, &idx); if (-1 == c) break; switch (c) { case 0: /* getopt_long() flag */ break; case 'd': dev_name = optarg; break; case 'h': usage(stdout, argc, argv); exit(EXIT_SUCCESS); case 'm': io = IO_METHOD_MMAP; break; case 'r': io = IO_METHOD_READ; break; case 'u': io = IO_METHOD_USERPTR; break; case 'o': out_buf++; break; case 'f': force_format=1; break; case 'F': force_format=2; break; case 'c': errno = 0; frame_count = strtol(optarg, NULL, 0); if (errno) errno_exit(optarg); break; default: usage(stderr, argc, argv); exit(EXIT_FAILURE); } } open_device(); init_device(); start_capturing(); mainloop(); stop_capturing(); uninit_device(); close_device(); fprintf(stderr, "\n"); return 0; } 

这是一个V4L2video捕捉示例的修改版本。 然后我知道,如果我已经输出到一个文件的stream,我将不得不运行此命令将原始格式转换为MP4格式:

 ffmpeg -f h264 -i output.raw -vcodec copy output.mp4 

而我正在使用的v4l2loopback程序是在这里: https : //github.com/umlaeute/v4l2loopback

——————更新——————

好的。 所以我从捕获程序中获取了pipe道到ffmpeg的工作。 它捕获,解码h264,我可以用这个命令把它写到一个mp4文件中:

./capture -F -d /dev/video0 -o | ffmpeg -f h264 -i - -vcodec copy out.mp4

现在我正在尝试使用此命令获取最后一个pipe道:

 ./capture -F -d /dev/video0 -o | ffmpeg -f h264 -i - -vcodec copy -f mp4 - | gst-launch-0.10 -v fdsrc ! v4l2sink device=/dev/video3 

我得到这些错误:

  • 复用器不支持不可search的输出
  • 无法为输出文件#0编写标题(不正确的编解码器参数?):无效的参数

有任何想法吗?

在你的最后一个命令中,你将MP4传输到GStreamer。 请参阅-f mp4 -部分:

./capture -F -d /dev/video0 -o | ffmpeg -f h264 -i - -vcodec copy -f mp4 - | gst-launch-0.10 -v fdsrc ! v4l2sink device=/dev/video3

你想要做的是在MP4里面传输H.264流。

尝试用-f mp4 - -f h264 -替换-f mp4 -

事实上,你完全可以跳过MP4的创建,只是:

./capture -F -d /dev/video0 -o | gst-launch-0.10 -v fdsrc ! v4l2sink device=/dev/video3

因为-F选项强制使用H.264。