libavdevice/v4l2.c - third_party/ffmpeg - Git at Google

 /*
  * Copyright (c) 2000,2001 Fabrice Bellard
  * Copyright (c) 2006 Luca Abeni
  *
  * This file is part of FFmpeg.
  *
  * FFmpeg is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Lesser General Public
  * License as published by the Free Software Foundation; either
  * version 2.1 of the License, or (at your option) any later version.
  *
  * FFmpeg is distributed in the hope that it will be useful,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  * Lesser General Public License for more details.
  *
  * You should have received a copy of the GNU Lesser General Public
  * License along with FFmpeg; if not, write to the Free Software
  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  */

 /**
  * @file
  * Video4Linux2 grab interface
  *
  * Part of this file is based on the V4L2 video capture example
  * (http://v4l2spec.bytesex.org/v4l2spec/capture.c)
  *
  * Thanks to Michael Niedermayer for providing the mapping between
  * V4L2_PIX_FMT_* and PIX_FMT_*
  */

 #undef __STRICT_ANSI__ //workaround due to broken kernel headers
 #include "config.h"
 #include <unistd.h>
 #include <fcntl.h>
 #include <sys/ioctl.h>
 #include <sys/mman.h>
 #include <sys/time.h>
 #if HAVE_SYS_VIDEOIO_H
 #include <sys/videoio.h>
 #else
 #include <asm/types.h>
 #include <linux/videodev2.h>
 #endif
 #include <time.h>
 #include <strings.h>
 #include "libavutil/imgutils.h"
 #include "libavutil/log.h"
 #include "libavutil/opt.h"
 #include "avdevice.h"
 #include "libavutil/parseutils.h"
 #include "libavutil/pixdesc.h"

 static const int desired_video_buffers = 256;

 enum io_method {
     io_read,
     io_mmap,
     io_userptr
 };

 struct video_data {
     AVClass *class;
     int fd;
     int frame_format; /* V4L2_PIX_FMT_* */
     enum io_method io_method;
     int width, height;
     int frame_size;
     int top_field_first;

     int buffers;
     void **buf_start;
     unsigned int *buf_len;
     char *standard;
     int channel;
     char *video_size; /**< String describing video size, set by a private option. */
     char *pixel_format; /**< Set by a private option. */
     char *framerate;    /**< Set by a private option. */
 };

 struct buff_data {
     int index;
     int fd;
 };

 struct fmt_map {
     enum PixelFormat ff_fmt;
     enum CodecID codec_id;
     uint32_t v4l2_fmt;
 };

 static struct fmt_map fmt_conversion_table[] = {
     //ff_fmt           codec_id           v4l2_fmt
     { PIX_FMT_YUV420P, CODEC_ID_RAWVIDEO, V4L2_PIX_FMT_YUV420  },
     { PIX_FMT_YUV422P, CODEC_ID_RAWVIDEO, V4L2_PIX_FMT_YUV422P },
     { PIX_FMT_YUYV422, CODEC_ID_RAWVIDEO, V4L2_PIX_FMT_YUYV    },
     { PIX_FMT_UYVY422, CODEC_ID_RAWVIDEO, V4L2_PIX_FMT_UYVY    },
     { PIX_FMT_YUV411P, CODEC_ID_RAWVIDEO, V4L2_PIX_FMT_YUV411P },
     { PIX_FMT_YUV410P, CODEC_ID_RAWVIDEO, V4L2_PIX_FMT_YUV410  },
     { PIX_FMT_RGB555,  CODEC_ID_RAWVIDEO, V4L2_PIX_FMT_RGB555  },
     { PIX_FMT_RGB565,  CODEC_ID_RAWVIDEO, V4L2_PIX_FMT_RGB565  },
     { PIX_FMT_BGR24,   CODEC_ID_RAWVIDEO, V4L2_PIX_FMT_BGR24   },
     { PIX_FMT_RGB24,   CODEC_ID_RAWVIDEO, V4L2_PIX_FMT_RGB24   },
     { PIX_FMT_BGRA,    CODEC_ID_RAWVIDEO, V4L2_PIX_FMT_BGR32   },
     { PIX_FMT_GRAY8,   CODEC_ID_RAWVIDEO, V4L2_PIX_FMT_GREY    },
     { PIX_FMT_NV12,    CODEC_ID_RAWVIDEO, V4L2_PIX_FMT_NV12    },
     { PIX_FMT_NONE,    CODEC_ID_MJPEG,    V4L2_PIX_FMT_MJPEG   },
     { PIX_FMT_NONE,    CODEC_ID_MJPEG,    V4L2_PIX_FMT_JPEG    },
 };

 static int device_open(AVFormatContext *ctx, uint32_t *capabilities)
 {
     struct v4l2_capability cap;
     int fd;
     int res, err;
     int flags = O_RDWR;

     if (ctx->flags & AVFMT_FLAG_NONBLOCK) {
         flags |= O_NONBLOCK;
     }
     fd = open(ctx->filename, flags, 0);
     if (fd < 0) {
         av_log(ctx, AV_LOG_ERROR, "Cannot open video device %s : %s\n",
                  ctx->filename, strerror(errno));
         return AVERROR(errno);
     }

     res = ioctl(fd, VIDIOC_QUERYCAP, &cap);
     // ENOIOCTLCMD definition only availble on __KERNEL__
     if (res < 0 && ((err = errno) == 515)) {
         av_log(ctx, AV_LOG_ERROR, "QUERYCAP not implemented, probably V4L device but not supporting V4L2\n");
         close(fd);

         return AVERROR(515);
     }
     if (res < 0) {
         av_log(ctx, AV_LOG_ERROR, "ioctl(VIDIOC_QUERYCAP): %s\n",
                  strerror(errno));
         close(fd);
         return AVERROR(err);
     }
     if ((cap.capabilities & V4L2_CAP_VIDEO_CAPTURE) == 0) {
         av_log(ctx, AV_LOG_ERROR, "Not a video capture device\n");
         close(fd);
         return AVERROR(ENODEV);
     }
     *capabilities = cap.capabilities;

     return fd;
 }

 static int device_init(AVFormatContext *ctx, int *width, int *height, uint32_t pix_fmt)
 {
     struct video_data *s = ctx->priv_data;
     int fd = s->fd;
     struct v4l2_format fmt = {0};
     int res;

     fmt.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
     fmt.fmt.pix.width = *width;
     fmt.fmt.pix.height = *height;
     fmt.fmt.pix.pixelformat = pix_fmt;
     fmt.fmt.pix.field = V4L2_FIELD_INTERLACED;
     res = ioctl(fd, VIDIOC_S_FMT, &fmt);
     if ((*width != fmt.fmt.pix.width) || (*height != fmt.fmt.pix.height)) {
         av_log(ctx, AV_LOG_INFO, "The V4L2 driver changed the video from %dx%d to %dx%d\n", *width, *height, fmt.fmt.pix.width, fmt.fmt.pix.height);
         *width = fmt.fmt.pix.width;
         *height = fmt.fmt.pix.height;
     }

     if (pix_fmt != fmt.fmt.pix.pixelformat) {
         av_log(ctx, AV_LOG_DEBUG, "The V4L2 driver changed the pixel format from 0x%08X to 0x%08X\n", pix_fmt, fmt.fmt.pix.pixelformat);
         res = -1;
     }

     return res;
 }

 static int first_field(int fd)
 {
     int res;
     v4l2_std_id std;

     res = ioctl(fd, VIDIOC_G_STD, &std);
     if (res < 0) {
         return 0;
     }
     if (std & V4L2_STD_NTSC) {
         return 0;
     }

     return 1;
 }

 static uint32_t fmt_ff2v4l(enum PixelFormat pix_fmt, enum CodecID codec_id)
 {
     int i;

     for (i = 0; i < FF_ARRAY_ELEMS(fmt_conversion_table); i++) {
         if ((codec_id == CODEC_ID_NONE ||
              fmt_conversion_table[i].codec_id == codec_id) &&
             (pix_fmt == PIX_FMT_NONE ||
              fmt_conversion_table[i].ff_fmt == pix_fmt)) {
             return fmt_conversion_table[i].v4l2_fmt;
         }
     }

     return 0;
 }

 static enum PixelFormat fmt_v4l2ff(uint32_t v4l2_fmt, enum CodecID codec_id)
 {
     int i;

     for (i = 0; i < FF_ARRAY_ELEMS(fmt_conversion_table); i++) {
         if (fmt_conversion_table[i].v4l2_fmt == v4l2_fmt &&
             fmt_conversion_table[i].codec_id == codec_id) {
             return fmt_conversion_table[i].ff_fmt;
         }
     }

     return PIX_FMT_NONE;
 }

 static enum CodecID fmt_v4l2codec(uint32_t v4l2_fmt)
 {
     int i;

     for (i = 0; i < FF_ARRAY_ELEMS(fmt_conversion_table); i++) {
         if (fmt_conversion_table[i].v4l2_fmt == v4l2_fmt) {
             return fmt_conversion_table[i].codec_id;
         }
     }

     return CODEC_ID_NONE;
 }

 static int mmap_init(AVFormatContext *ctx)
 {
     struct video_data *s = ctx->priv_data;
     struct v4l2_requestbuffers req = {0};
     int i, res;

     req.count = desired_video_buffers;
     req.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
     req.memory = V4L2_MEMORY_MMAP;
     res = ioctl(s->fd, VIDIOC_REQBUFS, &req);
     if (res < 0) {
         if (errno == EINVAL) {
             av_log(ctx, AV_LOG_ERROR, "Device does not support mmap\n");
         } else {
             av_log(ctx, AV_LOG_ERROR, "ioctl(VIDIOC_REQBUFS)\n");
         }
         return AVERROR(errno);
     }

     if (req.count < 2) {
         av_log(ctx, AV_LOG_ERROR, "Insufficient buffer memory\n");
         return AVERROR(ENOMEM);
     }
     s->buffers = req.count;
     s->buf_start = av_malloc(sizeof(void *) * s->buffers);
     if (s->buf_start == NULL) {
         av_log(ctx, AV_LOG_ERROR, "Cannot allocate buffer pointers\n");
         return AVERROR(ENOMEM);
     }
     s->buf_len = av_malloc(sizeof(unsigned int) * s->buffers);
     if (s->buf_len == NULL) {
         av_log(ctx, AV_LOG_ERROR, "Cannot allocate buffer sizes\n");
         av_free(s->buf_start);
         return AVERROR(ENOMEM);
     }

     for (i = 0; i < req.count; i++) {
         struct v4l2_buffer buf = {0};

         buf.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
         buf.memory = V4L2_MEMORY_MMAP;
         buf.index = i;
         res = ioctl(s->fd, VIDIOC_QUERYBUF, &buf);
         if (res < 0) {
             av_log(ctx, AV_LOG_ERROR, "ioctl(VIDIOC_QUERYBUF)\n");
             return AVERROR(errno);
         }

         s->buf_len[i] = buf.length;
         if (s->frame_size > 0 && s->buf_len[i] < s->frame_size) {
             av_log(ctx, AV_LOG_ERROR, "Buffer len [%d] = %d != %d\n", i, s->buf_len[i], s->frame_size);

             return -1;
         }
         s->buf_start[i] = mmap (NULL, buf.length,
                         PROT_READ | PROT_WRITE, MAP_SHARED, s->fd, buf.m.offset);
         if (s->buf_start[i] == MAP_FAILED) {
             av_log(ctx, AV_LOG_ERROR, "mmap: %s\n", strerror(errno));
             return AVERROR(errno);
         }
     }

     return 0;
 }

 static int read_init(AVFormatContext *ctx)
 {
     return -1;
 }

 static void mmap_release_buffer(AVPacket *pkt)
 {
     struct v4l2_buffer buf = {0};
     int res, fd;
     struct buff_data *buf_descriptor = pkt->priv;

     if (pkt->data == NULL) {
          return;
     }

     buf.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
     buf.memory = V4L2_MEMORY_MMAP;
     buf.index = buf_descriptor->index;
     fd = buf_descriptor->fd;
     av_free(buf_descriptor);

     res = ioctl(fd, VIDIOC_QBUF, &buf);
     if (res < 0) {
         av_log(NULL, AV_LOG_ERROR, "ioctl(VIDIOC_QBUF): %s\n", strerror(errno));
     }
     pkt->data = NULL;
     pkt->size = 0;
 }

 static int mmap_read_frame(AVFormatContext *ctx, AVPacket *pkt)
 {
     struct video_data *s = ctx->priv_data;
     struct v4l2_buffer buf = {0};
     struct buff_data *buf_descriptor;
     int res;

     buf.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
     buf.memory = V4L2_MEMORY_MMAP;

     /* FIXME: Some special treatment might be needed in case of loss of signal... */
     while ((res = ioctl(s->fd, VIDIOC_DQBUF, &buf)) < 0 && (errno == EINTR));
     if (res < 0) {
         if (errno == EAGAIN) {
             pkt->size = 0;
             return AVERROR(EAGAIN);
         }
         av_log(ctx, AV_LOG_ERROR, "ioctl(VIDIOC_DQBUF): %s\n", strerror(errno));

         return AVERROR(errno);
     }
     assert(buf.index < s->buffers);
     if (s->frame_size > 0 && buf.bytesused != s->frame_size) {
         av_log(ctx, AV_LOG_ERROR, "The v4l2 frame is %d bytes, but %d bytes are expected\n", buf.bytesused, s->frame_size);
         return AVERROR_INVALIDDATA;
     }

     /* Image is at s->buff_start[buf.index] */
     pkt->data= s->buf_start[buf.index];
     pkt->size = buf.bytesused;
     pkt->pts = buf.timestamp.tv_sec * INT64_C(1000000) + buf.timestamp.tv_usec;
     pkt->destruct = mmap_release_buffer;
     buf_descriptor = av_malloc(sizeof(struct buff_data));
     if (buf_descriptor == NULL) {
         /* Something went wrong... Since av_malloc() failed, we cannot even
          * allocate a buffer for memcopying into it
          */
         av_log(ctx, AV_LOG_ERROR, "Failed to allocate a buffer descriptor\n");
         res = ioctl(s->fd, VIDIOC_QBUF, &buf);

         return AVERROR(ENOMEM);
     }
     buf_descriptor->fd = s->fd;
     buf_descriptor->index = buf.index;
     pkt->priv = buf_descriptor;

     return s->buf_len[buf.index];
 }

 static int read_frame(AVFormatContext *ctx, AVPacket *pkt)
 {
     return -1;
 }

 static int mmap_start(AVFormatContext *ctx)
 {
     struct video_data *s = ctx->priv_data;
     enum v4l2_buf_type type;
     int i, res;

     for (i = 0; i < s->buffers; i++) {
         struct v4l2_buffer buf = {0};

         buf.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
         buf.memory = V4L2_MEMORY_MMAP;
         buf.index  = i;

         res = ioctl(s->fd, VIDIOC_QBUF, &buf);
         if (res < 0) {
             av_log(ctx, AV_LOG_ERROR, "ioctl(VIDIOC_QBUF): %s\n", strerror(errno));
             return AVERROR(errno);
         }
     }

     type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
     res = ioctl(s->fd, VIDIOC_STREAMON, &type);
     if (res < 0) {
         av_log(ctx, AV_LOG_ERROR, "ioctl(VIDIOC_STREAMON): %s\n", strerror(errno));
         return AVERROR(errno);
     }

     return 0;
 }

 static void mmap_close(struct video_data *s)
 {
     enum v4l2_buf_type type;
     int i;

     type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
     /* We do not check for the result, because we could
      * not do anything about it anyway...
      */
     ioctl(s->fd, VIDIOC_STREAMOFF, &type);
     for (i = 0; i < s->buffers; i++) {
         munmap(s->buf_start[i], s->buf_len[i]);
     }
     av_free(s->buf_start);
     av_free(s->buf_len);
 }

 static int v4l2_set_parameters(AVFormatContext *s1, AVFormatParameters *ap)
 {
     struct video_data *s = s1->priv_data;
     struct v4l2_input input = {0};
     struct v4l2_standard standard = {0};
     struct v4l2_streamparm streamparm = {0};
     struct v4l2_fract *tpf = &streamparm.parm.capture.timeperframe;
     int i, ret;
     AVRational fps;

     streamparm.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;

     if (s->framerate && (ret = av_parse_video_rate(&fps, s->framerate)) < 0) {
         av_log(s1, AV_LOG_ERROR, "Couldn't parse framerate.\n");
         return ret;
     }
 #if FF_API_FORMAT_PARAMETERS
     if (ap->channel > 0)
         s->channel = ap->channel;
     if (ap->time_base.num)
         fps = (AVRational){ap->time_base.den, ap->time_base.num};
 #endif

     /* set tv video input */
     input.index = s->channel;
     if (ioctl(s->fd, VIDIOC_ENUMINPUT, &input) < 0) {
         av_log(s1, AV_LOG_ERROR, "The V4L2 driver ioctl enum input failed:\n");
         return AVERROR(EIO);
     }

     av_log(s1, AV_LOG_DEBUG, "The V4L2 driver set input_id: %d, input: %s\n",
             s->channel, input.name);
     if (ioctl(s->fd, VIDIOC_S_INPUT, &input.index) < 0) {
         av_log(s1, AV_LOG_ERROR, "The V4L2 driver ioctl set input(%d) failed\n",
                 s->channel);
         return AVERROR(EIO);
     }

 #if FF_API_FORMAT_PARAMETERS
     if (ap->standard) {
         av_freep(&s->standard);
         s->standard = av_strdup(ap->standard);
     }
 #endif

     if (s->standard) {
         av_log(s1, AV_LOG_DEBUG, "The V4L2 driver set standard: %s\n",
                s->standard);
         /* set tv standard */
         for (i = 0;; i++) {
             standard.index = i;
             ret = ioctl(s->fd, VIDIOC_ENUMSTD, &standard);
             if (ret < 0 || !strcasecmp(standard.name, s->standard))
                 break;
         }
         if (ret < 0) {
             av_log(s1, AV_LOG_ERROR, "Unknown standard '%s'\n", s->standard);
             return ret;
         }

         av_log(s1, AV_LOG_DEBUG, "The V4L2 driver set standard: %s, id: %"PRIu64"\n",
                s->standard, (uint64_t)standard.id);
         if (ioctl(s->fd, VIDIOC_S_STD, &standard.id) < 0) {
             av_log(s1, AV_LOG_ERROR, "The V4L2 driver ioctl set standard(%s) failed\n",
                    s->standard);
             return AVERROR(EIO);
         }
     }

     if (fps.num && fps.den) {
         av_log(s1, AV_LOG_DEBUG, "Setting time per frame to %d/%d\n",
                fps.den, fps.num);
         tpf->numerator   = fps.den;
         tpf->denominator = fps.num;
         if (ioctl(s->fd, VIDIOC_S_PARM, &streamparm) != 0) {
             av_log(s1, AV_LOG_ERROR,
                    "ioctl set time per frame(%d/%d) failed\n",
                    fps.den, fps.num);
             return AVERROR(EIO);
         }

         if (fps.num != tpf->denominator ||
             fps.den != tpf->numerator) {
             av_log(s1, AV_LOG_INFO,
                    "The driver changed the time per frame from %d/%d to %d/%d\n",
                    fps.den, fps.num,
                    tpf->numerator, tpf->denominator);
         }
     } else {
         /* if timebase value is not set, read the timebase value from the driver */
         if (ioctl(s->fd, VIDIOC_G_PARM, &streamparm) != 0) {
             av_log(s1, AV_LOG_ERROR, "ioctl(VIDIOC_G_PARM): %s\n", strerror(errno));
             return AVERROR(errno);
         }
     }
     s1->streams[0]->codec->time_base.den = tpf->denominator;
     s1->streams[0]->codec->time_base.num = tpf->numerator;

     return 0;
 }

 static uint32_t device_try_init(AVFormatContext *s1,
                                 enum PixelFormat pix_fmt,
                                 int *width,
                                 int *height,
                                 enum CodecID *codec_id)
 {
     uint32_t desired_format = fmt_ff2v4l(pix_fmt, s1->video_codec_id);

     if (desired_format == 0 ||
         device_init(s1, width, height, desired_format) < 0) {
         int i;

         desired_format = 0;
         for (i = 0; i<FF_ARRAY_ELEMS(fmt_conversion_table); i++) {
             if (s1->video_codec_id == CODEC_ID_NONE ||
                 fmt_conversion_table[i].codec_id == s1->video_codec_id) {
                 desired_format = fmt_conversion_table[i].v4l2_fmt;
                 if (device_init(s1, width, height, desired_format) >= 0) {
                     break;
                 }
                 desired_format = 0;
             }
         }
     }
     if (desired_format != 0) {
         *codec_id = fmt_v4l2codec(desired_format);
         assert(*codec_id != CODEC_ID_NONE);
     }

     return desired_format;
 }

 static int v4l2_read_header(AVFormatContext *s1, AVFormatParameters *ap)
 {
     struct video_data *s = s1->priv_data;
     AVStream *st;
     int res = 0;
     uint32_t desired_format, capabilities;
     enum CodecID codec_id;
     enum PixelFormat pix_fmt = PIX_FMT_NONE;

     st = av_new_stream(s1, 0);
     if (!st) {
         res = AVERROR(ENOMEM);
         goto out;
     }
     av_set_pts_info(st, 64, 1, 1000000); /* 64 bits pts in us */

     if (s->video_size && (res = av_parse_video_size(&s->width, &s->height, s->video_size)) < 0) {
         av_log(s1, AV_LOG_ERROR, "Couldn't parse video size.\n");
         goto out;
     }
     if (s->pixel_format && (pix_fmt = av_get_pix_fmt(s->pixel_format)) == PIX_FMT_NONE) {
         av_log(s1, AV_LOG_ERROR, "No such pixel format: %s.\n", s->pixel_format);
         res = AVERROR(EINVAL);
         goto out;
     }
 #if FF_API_FORMAT_PARAMETERS
     if (ap->width > 0)
         s->width  = ap->width;
     if (ap->height > 0)
         s->height = ap->height;
     if (ap->pix_fmt)
         pix_fmt = ap->pix_fmt;
 #endif

     capabilities = 0;
     s->fd = device_open(s1, &capabilities);
     if (s->fd < 0) {
         res = AVERROR(EIO);
         goto out;
     }
     av_log(s1, AV_LOG_VERBOSE, "[%d]Capabilities: %x\n", s->fd, capabilities);

     if (!s->width && !s->height) {
         struct v4l2_format fmt;

         av_log(s1, AV_LOG_VERBOSE, "Querying the device for the current frame size\n");
         fmt.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
         if (ioctl(s->fd, VIDIOC_G_FMT, &fmt) < 0) {
             av_log(s1, AV_LOG_ERROR, "ioctl(VIDIOC_G_FMT): %s\n", strerror(errno));
             res = AVERROR(errno);
             goto out;
         }
         s->width  = fmt.fmt.pix.width;
         s->height = fmt.fmt.pix.height;
         av_log(s1, AV_LOG_VERBOSE, "Setting frame size to %dx%d\n", s->width, s->height);
     }

     desired_format = device_try_init(s1, pix_fmt, &s->width, &s->height, &codec_id);
     if (desired_format == 0) {
         av_log(s1, AV_LOG_ERROR, "Cannot find a proper format for "
                "codec_id %d, pix_fmt %d.\n", s1->video_codec_id, pix_fmt);
         close(s->fd);

         res = AVERROR(EIO);
         goto out;
     }
     if ((res = av_image_check_size(s->width, s->height, 0, s1) < 0))
         goto out;
     s->frame_format = desired_format;

     if ((res = v4l2_set_parameters(s1, ap) < 0))
         goto out;

     st->codec->pix_fmt = fmt_v4l2ff(desired_format, codec_id);
     s->frame_size = avpicture_get_size(st->codec->pix_fmt, s->width, s->height);
     if (capabilities & V4L2_CAP_STREAMING) {
         s->io_method = io_mmap;
         res = mmap_init(s1);
         if (res == 0) {
             res = mmap_start(s1);
         }
     } else {
         s->io_method = io_read;
         res = read_init(s1);
     }
     if (res < 0) {
         close(s->fd);
         res = AVERROR(EIO);
         goto out;
     }
     s->top_field_first = first_field(s->fd);

     st->codec->codec_type = AVMEDIA_TYPE_VIDEO;
     st->codec->codec_id = codec_id;
     st->codec->width = s->width;
     st->codec->height = s->height;
     st->codec->bit_rate = s->frame_size * 1/av_q2d(st->codec->time_base) * 8;

 out:
     return res;
 }

 static int v4l2_read_packet(AVFormatContext *s1, AVPacket *pkt)
 {
     struct video_data *s = s1->priv_data;
     int res;

     if (s->io_method == io_mmap) {
         av_init_packet(pkt);
         res = mmap_read_frame(s1, pkt);
     } else if (s->io_method == io_read) {
         if (av_new_packet(pkt, s->frame_size) < 0)
             return AVERROR(EIO);

         res = read_frame(s1, pkt);
     } else {
         return AVERROR(EIO);
     }
     if (res < 0) {
         return res;
     }

     if (s1->streams[0]->codec->coded_frame) {
         s1->streams[0]->codec->coded_frame->interlaced_frame = 1;
         s1->streams[0]->codec->coded_frame->top_field_first = s->top_field_first;
     }

     return pkt->size;
 }

 static int v4l2_read_close(AVFormatContext *s1)
 {
     struct video_data *s = s1->priv_data;

     if (s->io_method == io_mmap) {
         mmap_close(s);
     }

     close(s->fd);
     return 0;
 }

 #define OFFSET(x) offsetof(struct video_data, x)
 #define DEC AV_OPT_FLAG_DECODING_PARAM

 static const AVOption options[] = {
     { "standard", "", OFFSET(standard), FF_OPT_TYPE_STRING, {.str = NULL }, 0, 0, AV_OPT_FLAG_DECODING_PARAM },
     { "channel",  "", OFFSET(channel),  FF_OPT_TYPE_INT,    {.dbl = 0 }, 0, INT_MAX, AV_OPT_FLAG_DECODING_PARAM },
     { "video_size", "A string describing frame size, such as 640x480 or hd720.", OFFSET(video_size), FF_OPT_TYPE_STRING, {.str = NULL}, 0, 0, DEC },
     { "pixel_format", "", OFFSET(pixel_format), FF_OPT_TYPE_STRING, {.str = NULL}, 0, 0, DEC },
     { "framerate", "", OFFSET(framerate), FF_OPT_TYPE_STRING, {.str = NULL}, 0, 0, DEC },
     { NULL },
 };

 static const AVClass v4l2_class = {
     .class_name = "V4L2 indev",
     .item_name  = av_default_item_name,
     .option     = options,
     .version    = LIBAVUTIL_VERSION_INT,
 };

 AVInputFormat ff_v4l2_demuxer = {
     "video4linux2",
     NULL_IF_CONFIG_SMALL("Video4Linux2 device grab"),
     sizeof(struct video_data),
     NULL,
     v4l2_read_header,
     v4l2_read_packet,
     v4l2_read_close,
     .flags = AVFMT_NOFILE,
     .priv_class = &v4l2_class,
 };
	/*
	* Copyright (c) 2000,2001 Fabrice Bellard
	* Copyright (c) 2006 Luca Abeni
	*
	* This file is part of FFmpeg.
	*
	* FFmpeg is free software; you can redistribute it and/or
	* modify it under the terms of the GNU Lesser General Public
	* License as published by the Free Software Foundation; either
	* version 2.1 of the License, or (at your option) any later version.
	*
	* FFmpeg is distributed in the hope that it will be useful,
	* but WITHOUT ANY WARRANTY; without even the implied warranty of
	* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
	* Lesser General Public License for more details.
	*
	* You should have received a copy of the GNU Lesser General Public
	* License along with FFmpeg; if not, write to the Free Software
	* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
	*/

	/**
	* @file
	* Video4Linux2 grab interface
	*
	* Part of this file is based on the V4L2 video capture example
	* (http://v4l2spec.bytesex.org/v4l2spec/capture.c)
	*
	* Thanks to Michael Niedermayer for providing the mapping between
	* V4L2_PIX_FMT_* and PIX_FMT_*
	*/

	#undef __STRICT_ANSI__ //workaround due to broken kernel headers
	#include "config.h"
	#include <unistd.h>
	#include <fcntl.h>
	#include <sys/ioctl.h>
	#include <sys/mman.h>
	#include <sys/time.h>
	#if HAVE_SYS_VIDEOIO_H
	#include <sys/videoio.h>
	#else
	#include <asm/types.h>
	#include <linux/videodev2.h>
	#endif
	#include <time.h>
	#include <strings.h>
	#include "libavutil/imgutils.h"
	#include "libavutil/log.h"
	#include "libavutil/opt.h"
	#include "avdevice.h"
	#include "libavutil/parseutils.h"
	#include "libavutil/pixdesc.h"

	static const int desired_video_buffers = 256;

	enum io_method {
	io_read,
	io_mmap,
	io_userptr
	};

	struct video_data {
	AVClass *class;
	int fd;
	int frame_format; /* V4L2_PIX_FMT_* */
	enum io_method io_method;
	int width, height;
	int frame_size;
	int top_field_first;

	int buffers;
	void **buf_start;
	unsigned int *buf_len;
	char *standard;
	int channel;
	char video_size; /< String describing video size, set by a private option. /
	char pixel_format; /< Set by a private option. /
	char framerate; /< Set by a private option. /
	};

	struct buff_data {
	int index;
	int fd;
	};

	struct fmt_map {
	enum PixelFormat ff_fmt;
	enum CodecID codec_id;
	uint32_t v4l2_fmt;
	};

	static struct fmt_map fmt_conversion_table[] = {
	//ff_fmt codec_id v4l2_fmt
	{ PIX_FMT_YUV420P, CODEC_ID_RAWVIDEO, V4L2_PIX_FMT_YUV420 },
	{ PIX_FMT_YUV422P, CODEC_ID_RAWVIDEO, V4L2_PIX_FMT_YUV422P },
	{ PIX_FMT_YUYV422, CODEC_ID_RAWVIDEO, V4L2_PIX_FMT_YUYV },
	{ PIX_FMT_UYVY422, CODEC_ID_RAWVIDEO, V4L2_PIX_FMT_UYVY },
	{ PIX_FMT_YUV411P, CODEC_ID_RAWVIDEO, V4L2_PIX_FMT_YUV411P },
	{ PIX_FMT_YUV410P, CODEC_ID_RAWVIDEO, V4L2_PIX_FMT_YUV410 },
	{ PIX_FMT_RGB555, CODEC_ID_RAWVIDEO, V4L2_PIX_FMT_RGB555 },
	{ PIX_FMT_RGB565, CODEC_ID_RAWVIDEO, V4L2_PIX_FMT_RGB565 },
	{ PIX_FMT_BGR24, CODEC_ID_RAWVIDEO, V4L2_PIX_FMT_BGR24 },
	{ PIX_FMT_RGB24, CODEC_ID_RAWVIDEO, V4L2_PIX_FMT_RGB24 },
	{ PIX_FMT_BGRA, CODEC_ID_RAWVIDEO, V4L2_PIX_FMT_BGR32 },
	{ PIX_FMT_GRAY8, CODEC_ID_RAWVIDEO, V4L2_PIX_FMT_GREY },
	{ PIX_FMT_NV12, CODEC_ID_RAWVIDEO, V4L2_PIX_FMT_NV12 },
	{ PIX_FMT_NONE, CODEC_ID_MJPEG, V4L2_PIX_FMT_MJPEG },
	{ PIX_FMT_NONE, CODEC_ID_MJPEG, V4L2_PIX_FMT_JPEG },
	};

	static int device_open(AVFormatContext ctx, uint32_t capabilities)
	{
	struct v4l2_capability cap;
	int fd;
	int res, err;
	int flags = O_RDWR;

	if (ctx->flags & AVFMT_FLAG_NONBLOCK) {
	flags \|= O_NONBLOCK;
	}
	fd = open(ctx->filename, flags, 0);
	if (fd < 0) {
	av_log(ctx, AV_LOG_ERROR, "Cannot open video device %s : %s\n",
	ctx->filename, strerror(errno));
	return AVERROR(errno);
	}

	res = ioctl(fd, VIDIOC_QUERYCAP, &cap);
	// ENOIOCTLCMD definition only availble on __KERNEL__
	if (res < 0 && ((err = errno) == 515)) {
	av_log(ctx, AV_LOG_ERROR, "QUERYCAP not implemented, probably V4L device but not supporting V4L2\n");
	close(fd);

	return AVERROR(515);
	}
	if (res < 0) {
	av_log(ctx, AV_LOG_ERROR, "ioctl(VIDIOC_QUERYCAP): %s\n",
	strerror(errno));
	close(fd);
	return AVERROR(err);
	}
	if ((cap.capabilities & V4L2_CAP_VIDEO_CAPTURE) == 0) {
	av_log(ctx, AV_LOG_ERROR, "Not a video capture device\n");
	close(fd);
	return AVERROR(ENODEV);
	}
	*capabilities = cap.capabilities;

	return fd;
	}

	static int device_init(AVFormatContext ctx, int width, int *height, uint32_t pix_fmt)
	{
	struct video_data *s = ctx->priv_data;
	int fd = s->fd;
	struct v4l2_format fmt = {0};
	int res;

	fmt.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
	fmt.fmt.pix.width = *width;
	fmt.fmt.pix.height = *height;
	fmt.fmt.pix.pixelformat = pix_fmt;
	fmt.fmt.pix.field = V4L2_FIELD_INTERLACED;
	res = ioctl(fd, VIDIOC_S_FMT, &fmt);
	if ((width != fmt.fmt.pix.width) \|\| (height != fmt.fmt.pix.height)) {
	av_log(ctx, AV_LOG_INFO, "The V4L2 driver changed the video from %dx%d to %dx%d\n", width, height, fmt.fmt.pix.width, fmt.fmt.pix.height);
	*width = fmt.fmt.pix.width;
	*height = fmt.fmt.pix.height;
	}

	if (pix_fmt != fmt.fmt.pix.pixelformat) {
	av_log(ctx, AV_LOG_DEBUG, "The V4L2 driver changed the pixel format from 0x%08X to 0x%08X\n", pix_fmt, fmt.fmt.pix.pixelformat);
	res = -1;
	}

	return res;
	}

	static int first_field(int fd)
	{
	int res;
	v4l2_std_id std;

	res = ioctl(fd, VIDIOC_G_STD, &std);
	if (res < 0) {
	return 0;
	}
	if (std & V4L2_STD_NTSC) {
	return 0;
	}

	return 1;
	}

	static uint32_t fmt_ff2v4l(enum PixelFormat pix_fmt, enum CodecID codec_id)
	{
	int i;

	for (i = 0; i < FF_ARRAY_ELEMS(fmt_conversion_table); i++) {
	if ((codec_id == CODEC_ID_NONE \|\|
	fmt_conversion_table[i].codec_id == codec_id) &&
	(pix_fmt == PIX_FMT_NONE \|\|
	fmt_conversion_table[i].ff_fmt == pix_fmt)) {
	return fmt_conversion_table[i].v4l2_fmt;
	}
	}

	return 0;
	}

	static enum PixelFormat fmt_v4l2ff(uint32_t v4l2_fmt, enum CodecID codec_id)
	{
	int i;

	for (i = 0; i < FF_ARRAY_ELEMS(fmt_conversion_table); i++) {
	if (fmt_conversion_table[i].v4l2_fmt == v4l2_fmt &&
	fmt_conversion_table[i].codec_id == codec_id) {
	return fmt_conversion_table[i].ff_fmt;
	}
	}

	return PIX_FMT_NONE;
	}

	static enum CodecID fmt_v4l2codec(uint32_t v4l2_fmt)
	{
	int i;

	for (i = 0; i < FF_ARRAY_ELEMS(fmt_conversion_table); i++) {
	if (fmt_conversion_table[i].v4l2_fmt == v4l2_fmt) {
	return fmt_conversion_table[i].codec_id;
	}
	}

	return CODEC_ID_NONE;
	}

	static int mmap_init(AVFormatContext *ctx)
	{
	struct video_data *s = ctx->priv_data;
	struct v4l2_requestbuffers req = {0};
	int i, res;

	req.count = desired_video_buffers;
	req.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
	req.memory = V4L2_MEMORY_MMAP;
	res = ioctl(s->fd, VIDIOC_REQBUFS, &req);
	if (res < 0) {
	if (errno == EINVAL) {
	av_log(ctx, AV_LOG_ERROR, "Device does not support mmap\n");
	} else {
	av_log(ctx, AV_LOG_ERROR, "ioctl(VIDIOC_REQBUFS)\n");
	}
	return AVERROR(errno);
	}

	if (req.count < 2) {
	av_log(ctx, AV_LOG_ERROR, "Insufficient buffer memory\n");
	return AVERROR(ENOMEM);
	}
	s->buffers = req.count;
	s->buf_start = av_malloc(sizeof(void ) s->buffers);
	if (s->buf_start == NULL) {
	av_log(ctx, AV_LOG_ERROR, "Cannot allocate buffer pointers\n");
	return AVERROR(ENOMEM);
	}
	s->buf_len = av_malloc(sizeof(unsigned int) * s->buffers);
	if (s->buf_len == NULL) {
	av_log(ctx, AV_LOG_ERROR, "Cannot allocate buffer sizes\n");
	av_free(s->buf_start);
	return AVERROR(ENOMEM);
	}

	for (i = 0; i < req.count; i++) {
	struct v4l2_buffer buf = {0};

	buf.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
	buf.memory = V4L2_MEMORY_MMAP;
	buf.index = i;
	res = ioctl(s->fd, VIDIOC_QUERYBUF, &buf);
	if (res < 0) {
	av_log(ctx, AV_LOG_ERROR, "ioctl(VIDIOC_QUERYBUF)\n");
	return AVERROR(errno);
	}

	s->buf_len[i] = buf.length;
	if (s->frame_size > 0 && s->buf_len[i] < s->frame_size) {
	av_log(ctx, AV_LOG_ERROR, "Buffer len [%d] = %d != %d\n", i, s->buf_len[i], s->frame_size);

	return -1;
	}
	s->buf_start[i] = mmap (NULL, buf.length,
	PROT_READ \| PROT_WRITE, MAP_SHARED, s->fd, buf.m.offset);
	if (s->buf_start[i] == MAP_FAILED) {
	av_log(ctx, AV_LOG_ERROR, "mmap: %s\n", strerror(errno));
	return AVERROR(errno);
	}
	}

	return 0;
	}

	static int read_init(AVFormatContext *ctx)
	{
	return -1;
	}

	static void mmap_release_buffer(AVPacket *pkt)
	{
	struct v4l2_buffer buf = {0};
	int res, fd;
	struct buff_data *buf_descriptor = pkt->priv;

	if (pkt->data == NULL) {
	return;
	}

	buf.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
	buf.memory = V4L2_MEMORY_MMAP;
	buf.index = buf_descriptor->index;
	fd = buf_descriptor->fd;
	av_free(buf_descriptor);

	res = ioctl(fd, VIDIOC_QBUF, &buf);
	if (res < 0) {
	av_log(NULL, AV_LOG_ERROR, "ioctl(VIDIOC_QBUF): %s\n", strerror(errno));
	}
	pkt->data = NULL;
	pkt->size = 0;
	}

	static int mmap_read_frame(AVFormatContext ctx, AVPacket pkt)
	{
	struct video_data *s = ctx->priv_data;
	struct v4l2_buffer buf = {0};
	struct buff_data *buf_descriptor;
	int res;

	buf.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
	buf.memory = V4L2_MEMORY_MMAP;

	/* FIXME: Some special treatment might be needed in case of loss of signal... */
	while ((res = ioctl(s->fd, VIDIOC_DQBUF, &buf)) < 0 && (errno == EINTR));
	if (res < 0) {
	if (errno == EAGAIN) {
	pkt->size = 0;
	return AVERROR(EAGAIN);
	}
	av_log(ctx, AV_LOG_ERROR, "ioctl(VIDIOC_DQBUF): %s\n", strerror(errno));

	return AVERROR(errno);
	}
	assert(buf.index < s->buffers);
	if (s->frame_size > 0 && buf.bytesused != s->frame_size) {
	av_log(ctx, AV_LOG_ERROR, "The v4l2 frame is %d bytes, but %d bytes are expected\n", buf.bytesused, s->frame_size);
	return AVERROR_INVALIDDATA;
	}

	/* Image is at s->buff_start[buf.index] */
	pkt->data= s->buf_start[buf.index];
	pkt->size = buf.bytesused;
	pkt->pts = buf.timestamp.tv_sec * INT64_C(1000000) + buf.timestamp.tv_usec;
	pkt->destruct = mmap_release_buffer;
	buf_descriptor = av_malloc(sizeof(struct buff_data));
	if (buf_descriptor == NULL) {
	/* Something went wrong... Since av_malloc() failed, we cannot even
	* allocate a buffer for memcopying into it
	*/
	av_log(ctx, AV_LOG_ERROR, "Failed to allocate a buffer descriptor\n");
	res = ioctl(s->fd, VIDIOC_QBUF, &buf);

	return AVERROR(ENOMEM);
	}
	buf_descriptor->fd = s->fd;
	buf_descriptor->index = buf.index;
	pkt->priv = buf_descriptor;

	return s->buf_len[buf.index];
	}

	static int read_frame(AVFormatContext ctx, AVPacket pkt)
	{
	return -1;
	}

	static int mmap_start(AVFormatContext *ctx)
	{
	struct video_data *s = ctx->priv_data;
	enum v4l2_buf_type type;
	int i, res;

	for (i = 0; i < s->buffers; i++) {
	struct v4l2_buffer buf = {0};

	buf.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
	buf.memory = V4L2_MEMORY_MMAP;
	buf.index = i;

	res = ioctl(s->fd, VIDIOC_QBUF, &buf);
	if (res < 0) {
	av_log(ctx, AV_LOG_ERROR, "ioctl(VIDIOC_QBUF): %s\n", strerror(errno));
	return AVERROR(errno);
	}
	}

	type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
	res = ioctl(s->fd, VIDIOC_STREAMON, &type);
	if (res < 0) {
	av_log(ctx, AV_LOG_ERROR, "ioctl(VIDIOC_STREAMON): %s\n", strerror(errno));
	return AVERROR(errno);
	}

	return 0;
	}

	static void mmap_close(struct video_data *s)
	{
	enum v4l2_buf_type type;
	int i;

	type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
	/* We do not check for the result, because we could
	* not do anything about it anyway...
	*/
	ioctl(s->fd, VIDIOC_STREAMOFF, &type);
	for (i = 0; i < s->buffers; i++) {
	munmap(s->buf_start[i], s->buf_len[i]);
	}
	av_free(s->buf_start);
	av_free(s->buf_len);
	}

	static int v4l2_set_parameters(AVFormatContext s1, AVFormatParameters ap)
	{
	struct video_data *s = s1->priv_data;
	struct v4l2_input input = {0};
	struct v4l2_standard standard = {0};
	struct v4l2_streamparm streamparm = {0};
	struct v4l2_fract *tpf = &streamparm.parm.capture.timeperframe;
	int i, ret;
	AVRational fps;

	streamparm.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;

	if (s->framerate && (ret = av_parse_video_rate(&fps, s->framerate)) < 0) {
	av_log(s1, AV_LOG_ERROR, "Couldn't parse framerate.\n");
	return ret;
	}
	#if FF_API_FORMAT_PARAMETERS
	if (ap->channel > 0)
	s->channel = ap->channel;
	if (ap->time_base.num)
	fps = (AVRational){ap->time_base.den, ap->time_base.num};
	#endif

	/* set tv video input */
	input.index = s->channel;
	if (ioctl(s->fd, VIDIOC_ENUMINPUT, &input) < 0) {
	av_log(s1, AV_LOG_ERROR, "The V4L2 driver ioctl enum input failed:\n");
	return AVERROR(EIO);
	}

	av_log(s1, AV_LOG_DEBUG, "The V4L2 driver set input_id: %d, input: %s\n",
	s->channel, input.name);
	if (ioctl(s->fd, VIDIOC_S_INPUT, &input.index) < 0) {
	av_log(s1, AV_LOG_ERROR, "The V4L2 driver ioctl set input(%d) failed\n",
	s->channel);
	return AVERROR(EIO);
	}

	#if FF_API_FORMAT_PARAMETERS
	if (ap->standard) {
	av_freep(&s->standard);
	s->standard = av_strdup(ap->standard);
	}
	#endif

	if (s->standard) {
	av_log(s1, AV_LOG_DEBUG, "The V4L2 driver set standard: %s\n",
	s->standard);
	/* set tv standard */
	for (i = 0;; i++) {
	standard.index = i;
	ret = ioctl(s->fd, VIDIOC_ENUMSTD, &standard);
	if (ret < 0 \|\| !strcasecmp(standard.name, s->standard))
	break;
	}
	if (ret < 0) {
	av_log(s1, AV_LOG_ERROR, "Unknown standard '%s'\n", s->standard);
	return ret;
	}

	av_log(s1, AV_LOG_DEBUG, "The V4L2 driver set standard: %s, id: %"PRIu64"\n",
	s->standard, (uint64_t)standard.id);
	if (ioctl(s->fd, VIDIOC_S_STD, &standard.id) < 0) {
	av_log(s1, AV_LOG_ERROR, "The V4L2 driver ioctl set standard(%s) failed\n",
	s->standard);
	return AVERROR(EIO);
	}
	}

	if (fps.num && fps.den) {
	av_log(s1, AV_LOG_DEBUG, "Setting time per frame to %d/%d\n",
	fps.den, fps.num);
	tpf->numerator = fps.den;
	tpf->denominator = fps.num;
	if (ioctl(s->fd, VIDIOC_S_PARM, &streamparm) != 0) {
	av_log(s1, AV_LOG_ERROR,
	"ioctl set time per frame(%d/%d) failed\n",
	fps.den, fps.num);
	return AVERROR(EIO);
	}

	if (fps.num != tpf->denominator \|\|
	fps.den != tpf->numerator) {
	av_log(s1, AV_LOG_INFO,
	"The driver changed the time per frame from %d/%d to %d/%d\n",
	fps.den, fps.num,
	tpf->numerator, tpf->denominator);
	}
	} else {
	/* if timebase value is not set, read the timebase value from the driver */
	if (ioctl(s->fd, VIDIOC_G_PARM, &streamparm) != 0) {
	av_log(s1, AV_LOG_ERROR, "ioctl(VIDIOC_G_PARM): %s\n", strerror(errno));
	return AVERROR(errno);
	}
	}
	s1->streams[0]->codec->time_base.den = tpf->denominator;
	s1->streams[0]->codec->time_base.num = tpf->numerator;

	return 0;
	}

	static uint32_t device_try_init(AVFormatContext *s1,
	enum PixelFormat pix_fmt,
	int *width,
	int *height,
	enum CodecID *codec_id)
	{
	uint32_t desired_format = fmt_ff2v4l(pix_fmt, s1->video_codec_id);

	if (desired_format == 0 \|\|
	device_init(s1, width, height, desired_format) < 0) {
	int i;

	desired_format = 0;
	for (i = 0; i<FF_ARRAY_ELEMS(fmt_conversion_table); i++) {
	if (s1->video_codec_id == CODEC_ID_NONE \|\|
	fmt_conversion_table[i].codec_id == s1->video_codec_id) {
	desired_format = fmt_conversion_table[i].v4l2_fmt;
	if (device_init(s1, width, height, desired_format) >= 0) {
	break;
	}
	desired_format = 0;
	}
	}
	}
	if (desired_format != 0) {
	*codec_id = fmt_v4l2codec(desired_format);
	assert(*codec_id != CODEC_ID_NONE);
	}

	return desired_format;
	}

	static int v4l2_read_header(AVFormatContext s1, AVFormatParameters ap)
	{
	struct video_data *s = s1->priv_data;
	AVStream *st;
	int res = 0;
	uint32_t desired_format, capabilities;
	enum CodecID codec_id;
	enum PixelFormat pix_fmt = PIX_FMT_NONE;

	st = av_new_stream(s1, 0);
	if (!st) {
	res = AVERROR(ENOMEM);
	goto out;
	}
	av_set_pts_info(st, 64, 1, 1000000); /* 64 bits pts in us */

	if (s->video_size && (res = av_parse_video_size(&s->width, &s->height, s->video_size)) < 0) {
	av_log(s1, AV_LOG_ERROR, "Couldn't parse video size.\n");
	goto out;
	}
	if (s->pixel_format && (pix_fmt = av_get_pix_fmt(s->pixel_format)) == PIX_FMT_NONE) {
	av_log(s1, AV_LOG_ERROR, "No such pixel format: %s.\n", s->pixel_format);
	res = AVERROR(EINVAL);
	goto out;
	}
	#if FF_API_FORMAT_PARAMETERS
	if (ap->width > 0)
	s->width = ap->width;
	if (ap->height > 0)
	s->height = ap->height;
	if (ap->pix_fmt)
	pix_fmt = ap->pix_fmt;
	#endif

	capabilities = 0;
	s->fd = device_open(s1, &capabilities);
	if (s->fd < 0) {
	res = AVERROR(EIO);
	goto out;
	}
	av_log(s1, AV_LOG_VERBOSE, "[%d]Capabilities: %x\n", s->fd, capabilities);

	if (!s->width && !s->height) {
	struct v4l2_format fmt;

	av_log(s1, AV_LOG_VERBOSE, "Querying the device for the current frame size\n");
	fmt.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
	if (ioctl(s->fd, VIDIOC_G_FMT, &fmt) < 0) {
	av_log(s1, AV_LOG_ERROR, "ioctl(VIDIOC_G_FMT): %s\n", strerror(errno));
	res = AVERROR(errno);
	goto out;
	}
	s->width = fmt.fmt.pix.width;
	s->height = fmt.fmt.pix.height;
	av_log(s1, AV_LOG_VERBOSE, "Setting frame size to %dx%d\n", s->width, s->height);
	}

	desired_format = device_try_init(s1, pix_fmt, &s->width, &s->height, &codec_id);
	if (desired_format == 0) {
	av_log(s1, AV_LOG_ERROR, "Cannot find a proper format for "
	"codec_id %d, pix_fmt %d.\n", s1->video_codec_id, pix_fmt);
	close(s->fd);

	res = AVERROR(EIO);
	goto out;
	}
	if ((res = av_image_check_size(s->width, s->height, 0, s1) < 0))
	goto out;
	s->frame_format = desired_format;

	if ((res = v4l2_set_parameters(s1, ap) < 0))
	goto out;

	st->codec->pix_fmt = fmt_v4l2ff(desired_format, codec_id);
	s->frame_size = avpicture_get_size(st->codec->pix_fmt, s->width, s->height);
	if (capabilities & V4L2_CAP_STREAMING) {
	s->io_method = io_mmap;
	res = mmap_init(s1);
	if (res == 0) {
	res = mmap_start(s1);
	}
	} else {
	s->io_method = io_read;
	res = read_init(s1);
	}
	if (res < 0) {
	close(s->fd);
	res = AVERROR(EIO);
	goto out;
	}
	s->top_field_first = first_field(s->fd);

	st->codec->codec_type = AVMEDIA_TYPE_VIDEO;
	st->codec->codec_id = codec_id;
	st->codec->width = s->width;
	st->codec->height = s->height;
	st->codec->bit_rate = s->frame_size * 1/av_q2d(st->codec->time_base) * 8;

	out:
	return res;
	}

	static int v4l2_read_packet(AVFormatContext s1, AVPacket pkt)
	{
	struct video_data *s = s1->priv_data;
	int res;

	if (s->io_method == io_mmap) {
	av_init_packet(pkt);
	res = mmap_read_frame(s1, pkt);
	} else if (s->io_method == io_read) {
	if (av_new_packet(pkt, s->frame_size) < 0)
	return AVERROR(EIO);

	res = read_frame(s1, pkt);
	} else {
	return AVERROR(EIO);
	}
	if (res < 0) {
	return res;
	}

	if (s1->streams[0]->codec->coded_frame) {
	s1->streams[0]->codec->coded_frame->interlaced_frame = 1;
	s1->streams[0]->codec->coded_frame->top_field_first = s->top_field_first;
	}

	return pkt->size;
	}

	static int v4l2_read_close(AVFormatContext *s1)
	{
	struct video_data *s = s1->priv_data;

	if (s->io_method == io_mmap) {
	mmap_close(s);
	}

	close(s->fd);
	return 0;
	}

	#define OFFSET(x) offsetof(struct video_data, x)
	#define DEC AV_OPT_FLAG_DECODING_PARAM

	static const AVOption options[] = {
	{ "standard", "", OFFSET(standard), FF_OPT_TYPE_STRING, {.str = NULL }, 0, 0, AV_OPT_FLAG_DECODING_PARAM },
	{ "channel", "", OFFSET(channel), FF_OPT_TYPE_INT, {.dbl = 0 }, 0, INT_MAX, AV_OPT_FLAG_DECODING_PARAM },
	{ "video_size", "A string describing frame size, such as 640x480 or hd720.", OFFSET(video_size), FF_OPT_TYPE_STRING, {.str = NULL}, 0, 0, DEC },
	{ "pixel_format", "", OFFSET(pixel_format), FF_OPT_TYPE_STRING, {.str = NULL}, 0, 0, DEC },
	{ "framerate", "", OFFSET(framerate), FF_OPT_TYPE_STRING, {.str = NULL}, 0, 0, DEC },
	{ NULL },
	};

	static const AVClass v4l2_class = {
	.class_name = "V4L2 indev",
	.item_name = av_default_item_name,
	.option = options,
	.version = LIBAVUTIL_VERSION_INT,
	};

	AVInputFormat ff_v4l2_demuxer = {
	"video4linux2",
	NULL_IF_CONFIG_SMALL("Video4Linux2 device grab"),
	sizeof(struct video_data),
	NULL,
	v4l2_read_header,
	v4l2_read_packet,
	v4l2_read_close,
	.flags = AVFMT_NOFILE,
	.priv_class = &v4l2_class,
	};