/*

  * 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={0};

     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,

 };