/*

  * 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://linuxtv.org/downloads/v4l-dvb-apis/capture-example.html)

  *
  * Thanks to Michael Niedermayer for providing the mapping between

  * V4L2_PIX_FMT_* and AV_PIX_FMT_*

  */
 

 #include <stdatomic.h>

 #include "v4l2-common.h"

 #include <dirent.h>

 #if CONFIG_LIBV4L2
 #include <libv4l2.h>
 #endif
 

 static const int desired_video_buffers = 256;
 

 #define V4L_ALLFORMATS  3
 #define V4L_RAWFORMATS  1
 #define V4L_COMPFORMATS 2

 /**
  * Return timestamps to the user exactly as returned by the kernel
  */
 #define V4L_TS_DEFAULT  0
 /**
  * Autodetect the kind of timestamps returned by the kernel and convert to
  * absolute (wall clock) timestamps.
  */
 #define V4L_TS_ABS      1
 /**
  * Assume kernel timestamps are from the monotonic clock and convert to
  * absolute timestamps.
  */
 #define V4L_TS_MONO2ABS 2
 
 /**
  * Once the kind of timestamps returned by the kernel have been detected,
  * the value of the timefilter (NULL or not) determines whether a conversion
  * takes place.
  */
 #define V4L_TS_CONVERT_READY V4L_TS_DEFAULT
 

 struct video_data {

     AVClass *class;

     int fd;

     int pixelformat; /* V4L2_PIX_FMT_* */

     int width, height;
     int frame_size;

     int interlaced;

     int top_field_first;

     int ts_mode;
     TimeFilter *timefilter;
     int64_t last_time_m;

 
     int buffers;

     atomic_int buffers_queued;

     void **buf_start;
     unsigned int *buf_len;

     char *standard;

     v4l2_std_id std_id;

     int channel;

     char *pixel_format; /**< Set by a private option. */

     int list_format;    /**< Set by a private option. */

     int list_standard;  /**< Set by a private option. */

     char *framerate;    /**< Set by a private option. */

 
     int use_libv4l2;
     int (*open_f)(const char *file, int oflag, ...);
     int (*close_f)(int fd);
     int (*dup_f)(int fd);
     int (*ioctl_f)(int fd, unsigned long int request, ...);
     ssize_t (*read_f)(int fd, void *buffer, size_t n);
     void *(*mmap_f)(void *start, size_t length, int prot, int flags, int fd, int64_t offset);
     int (*munmap_f)(void *_start, size_t length);

 };
 

 struct buff_data {

     struct video_data *s;

     int index;
 };
 

 static int device_open(AVFormatContext *ctx)

 {

     struct video_data *s = ctx->priv_data;

     struct v4l2_capability cap;
     int fd;

     int err;

     int flags = O_RDWR;

 #define SET_WRAPPERS(prefix) do {       \
     s->open_f   = prefix ## open;       \
     s->close_f  = prefix ## close;      \
     s->dup_f    = prefix ## dup;        \
     s->ioctl_f  = prefix ## ioctl;      \
     s->read_f   = prefix ## read;       \
     s->mmap_f   = prefix ## mmap;       \
     s->munmap_f = prefix ## munmap;     \
 } while (0)
 
     if (s->use_libv4l2) {
 #if CONFIG_LIBV4L2
         SET_WRAPPERS(v4l2_);
 #else

         av_log(ctx, AV_LOG_ERROR, "libavdevice is not built with libv4l2 support.\n");

         return AVERROR(EINVAL);
 #endif
     } else {
         SET_WRAPPERS();
     }
 
 #define v4l2_open   s->open_f
 #define v4l2_close  s->close_f
 #define v4l2_dup    s->dup_f
 #define v4l2_ioctl  s->ioctl_f
 #define v4l2_read   s->read_f
 #define v4l2_mmap   s->mmap_f
 #define v4l2_munmap s->munmap_f
 

     if (ctx->flags & AVFMT_FLAG_NONBLOCK) {
         flags |= O_NONBLOCK;
     }

     fd = v4l2_open(ctx->filename, flags, 0);

     if (fd < 0) {

         err = AVERROR(errno);

         av_log(ctx, AV_LOG_ERROR, "Cannot open video device %s: %s\n",

                ctx->filename, av_err2str(err));

         return err;

     }
 

     if (v4l2_ioctl(fd, VIDIOC_QUERYCAP, &cap) < 0) {

         err = AVERROR(errno);

         av_log(ctx, AV_LOG_ERROR, "ioctl(VIDIOC_QUERYCAP): %s\n",

                av_err2str(err));

         goto fail;

     }

     av_log(ctx, AV_LOG_VERBOSE, "fd:%d capabilities:%x\n",

            fd, cap.capabilities);
 
     if (!(cap.capabilities & V4L2_CAP_VIDEO_CAPTURE)) {
         av_log(ctx, AV_LOG_ERROR, "Not a video capture device.\n");

         err = AVERROR(ENODEV);

         goto fail;

     }

     if (!(cap.capabilities & V4L2_CAP_STREAMING)) {
         av_log(ctx, AV_LOG_ERROR,
                "The device does not support the streaming I/O method.\n");

         err = AVERROR(ENOSYS);

         goto fail;

     }
 
     return fd;

 
 fail:

     v4l2_close(fd);

     return err;

 }
 

 static int device_init(AVFormatContext *ctx, int *width, int *height,

                        uint32_t pixelformat)

 {

     struct video_data *s = ctx->priv_data;

     struct v4l2_format fmt = { .type = V4L2_BUF_TYPE_VIDEO_CAPTURE };

     int res = 0;

     fmt.fmt.pix.width = *width;
     fmt.fmt.pix.height = *height;
     fmt.fmt.pix.pixelformat = pixelformat;
     fmt.fmt.pix.field = V4L2_FIELD_ANY;

     /* Some drivers will fail and return EINVAL when the pixelformat
        is not supported (even if type field is valid and supported) */

     if (v4l2_ioctl(s->fd, VIDIOC_S_FMT, &fmt) < 0)

         res = AVERROR(errno);

     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 (pixelformat != fmt.fmt.pix.pixelformat) {

         av_log(ctx, AV_LOG_DEBUG,
                "The V4L2 driver changed the pixel format "
                "from 0x%08X to 0x%08X\n",

                pixelformat, fmt.fmt.pix.pixelformat);

         res = AVERROR(EINVAL);

     }
 

     if (fmt.fmt.pix.field == V4L2_FIELD_INTERLACED) {

         av_log(ctx, AV_LOG_DEBUG,
                "The V4L2 driver is using the interlaced mode\n");

         s->interlaced = 1;
     }
 

     return res;

 }
 

 static int first_field(const struct video_data *s)

 {
     int res;
     v4l2_std_id std;
 

     res = v4l2_ioctl(s->fd, VIDIOC_G_STD, &std);
     if (res < 0)

         return 0;

     if (std & V4L2_STD_NTSC)

         return 0;
 
     return 1;
 }
 

 #if HAVE_STRUCT_V4L2_FRMIVALENUM_DISCRETE

 static void list_framesizes(AVFormatContext *ctx, uint32_t pixelformat)

 {

     const struct video_data *s = ctx->priv_data;

     struct v4l2_frmsizeenum vfse = { .pixel_format = pixelformat };
 

     while(!v4l2_ioctl(s->fd, VIDIOC_ENUM_FRAMESIZES, &vfse)) {

         switch (vfse.type) {
         case V4L2_FRMSIZE_TYPE_DISCRETE:
             av_log(ctx, AV_LOG_INFO, " %ux%u",
                    vfse.discrete.width, vfse.discrete.height);
         break;
         case V4L2_FRMSIZE_TYPE_CONTINUOUS:
         case V4L2_FRMSIZE_TYPE_STEPWISE:
             av_log(ctx, AV_LOG_INFO, " {%u-%u, %u}x{%u-%u, %u}",
                    vfse.stepwise.min_width,
                    vfse.stepwise.max_width,
                    vfse.stepwise.step_width,
                    vfse.stepwise.min_height,
                    vfse.stepwise.max_height,
                    vfse.stepwise.step_height);
         }
         vfse.index++;
     }
 }
 #endif
 

 static void list_formats(AVFormatContext *ctx, int type)

 {

     const struct video_data *s = ctx->priv_data;

     struct v4l2_fmtdesc vfd = { .type = V4L2_BUF_TYPE_VIDEO_CAPTURE };
 

     while(!v4l2_ioctl(s->fd, VIDIOC_ENUM_FMT, &vfd)) {

         enum AVCodecID codec_id = ff_fmt_v4l2codec(vfd.pixelformat);
         enum AVPixelFormat pix_fmt = ff_fmt_v4l2ff(vfd.pixelformat, codec_id);

 
         vfd.index++;
 
         if (!(vfd.flags & V4L2_FMT_FLAG_COMPRESSED) &&
             type & V4L_RAWFORMATS) {
             const char *fmt_name = av_get_pix_fmt_name(pix_fmt);

             av_log(ctx, AV_LOG_INFO, "Raw       : %11s : %20s :",

                    fmt_name ? fmt_name : "Unsupported",
                    vfd.description);
         } else if (vfd.flags & V4L2_FMT_FLAG_COMPRESSED &&
                    type & V4L_COMPFORMATS) {

             const AVCodecDescriptor *desc = avcodec_descriptor_get(codec_id);

             av_log(ctx, AV_LOG_INFO, "Compressed: %11s : %20s :",

                    desc ? desc->name : "Unsupported",

                    vfd.description);
         } else {
             continue;
         }
 

 #ifdef V4L2_FMT_FLAG_EMULATED

         if (vfd.flags & V4L2_FMT_FLAG_EMULATED)
             av_log(ctx, AV_LOG_INFO, " Emulated :");

 #endif

 #if HAVE_STRUCT_V4L2_FRMIVALENUM_DISCRETE

         list_framesizes(ctx, vfd.pixelformat);

 #endif
         av_log(ctx, AV_LOG_INFO, "\n");
     }
 }
 

 static void list_standards(AVFormatContext *ctx)
 {
     int ret;
     struct video_data *s = ctx->priv_data;
     struct v4l2_standard standard;
 
     if (s->std_id == 0)
         return;
 
     for (standard.index = 0; ; standard.index++) {

         if (v4l2_ioctl(s->fd, VIDIOC_ENUMSTD, &standard) < 0) {
             ret = AVERROR(errno);
             if (ret == AVERROR(EINVAL)) {

                 break;

             } else {
                 av_log(ctx, AV_LOG_ERROR, "ioctl(VIDIOC_ENUMSTD): %s\n", av_err2str(ret));

                 return;
             }
         }

         av_log(ctx, AV_LOG_INFO, "%2d, %16"PRIx64", %s\n",
                standard.index, (uint64_t)standard.id, standard.name);

     }
 }
 

 static int mmap_init(AVFormatContext *ctx)

 {
     int i, res;

     struct video_data *s = ctx->priv_data;
     struct v4l2_requestbuffers req = {
         .type   = V4L2_BUF_TYPE_VIDEO_CAPTURE,
         .count  = desired_video_buffers,
         .memory = V4L2_MEMORY_MMAP
     };

     if (v4l2_ioctl(s->fd, VIDIOC_REQBUFS, &req) < 0) {
         res = AVERROR(errno);
         av_log(ctx, AV_LOG_ERROR, "ioctl(VIDIOC_REQBUFS): %s\n", av_err2str(res));
         return res;

     }
 
     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_array(s->buffers, sizeof(void *));

     if (!s->buf_start) {

         av_log(ctx, AV_LOG_ERROR, "Cannot allocate buffer pointers\n");

         return AVERROR(ENOMEM);

     }

     s->buf_len = av_malloc_array(s->buffers, sizeof(unsigned int));

     if (!s->buf_len) {

         av_log(ctx, AV_LOG_ERROR, "Cannot allocate buffer sizes\n");

         av_freep(&s->buf_start);

         return AVERROR(ENOMEM);

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

         struct v4l2_buffer buf = {
             .type   = V4L2_BUF_TYPE_VIDEO_CAPTURE,
             .index  = i,
             .memory = V4L2_MEMORY_MMAP
         };

         if (v4l2_ioctl(s->fd, VIDIOC_QUERYBUF, &buf) < 0) {
             res = AVERROR(errno);
             av_log(ctx, AV_LOG_ERROR, "ioctl(VIDIOC_QUERYBUF): %s\n", av_err2str(res));
             return res;

         }
 
         s->buf_len[i] = buf.length;

         if (s->frame_size > 0 && s->buf_len[i] < s->frame_size) {

             av_log(ctx, AV_LOG_ERROR,

                    "buf_len[%d] = %d < expected frame size %d\n",

                    i, s->buf_len[i], s->frame_size);

             return AVERROR(ENOMEM);

         }

         s->buf_start[i] = v4l2_mmap(NULL, buf.length,

                                PROT_READ | PROT_WRITE, MAP_SHARED,
                                s->fd, buf.m.offset);
 

         if (s->buf_start[i] == MAP_FAILED) {

             res = AVERROR(errno);
             av_log(ctx, AV_LOG_ERROR, "mmap: %s\n", av_err2str(res));
             return res;

         }
     }
 
     return 0;
 }
 

 static int enqueue_buffer(struct video_data *s, struct v4l2_buffer *buf)
 {
     int res = 0;
 
     if (v4l2_ioctl(s->fd, VIDIOC_QBUF, buf) < 0) {
         res = AVERROR(errno);
         av_log(NULL, AV_LOG_ERROR, "ioctl(VIDIOC_QBUF): %s\n", av_err2str(res));
     } else {

         atomic_fetch_add(&s->buffers_queued, 1);

     }
 
     return res;
 }
 

 static void mmap_release_buffer(void *opaque, uint8_t *data)

 {

     struct v4l2_buffer buf = { 0 };

     struct buff_data *buf_descriptor = opaque;
     struct video_data *s = buf_descriptor->s;

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

     enqueue_buffer(s, &buf);

 }
 

 #if HAVE_CLOCK_GETTIME && defined(CLOCK_MONOTONIC)
 static int64_t av_gettime_monotonic(void)
 {

     return av_gettime_relative();

 }
 #endif
 
 static int init_convert_timestamp(AVFormatContext *ctx, int64_t ts)
 {
     struct video_data *s = ctx->priv_data;
     int64_t now;
 
     now = av_gettime();
     if (s->ts_mode == V4L_TS_ABS &&
         ts <= now + 1 * AV_TIME_BASE && ts >= now - 10 * AV_TIME_BASE) {
         av_log(ctx, AV_LOG_INFO, "Detected absolute timestamps\n");
         s->ts_mode = V4L_TS_CONVERT_READY;
         return 0;
     }
 #if HAVE_CLOCK_GETTIME && defined(CLOCK_MONOTONIC)

     if (ctx->streams[0]->avg_frame_rate.num) {
         now = av_gettime_monotonic();
         if (s->ts_mode == V4L_TS_MONO2ABS ||
             (ts <= now + 1 * AV_TIME_BASE && ts >= now - 10 * AV_TIME_BASE)) {
             AVRational tb = {AV_TIME_BASE, 1};
             int64_t period = av_rescale_q(1, tb, ctx->streams[0]->avg_frame_rate);
             av_log(ctx, AV_LOG_INFO, "Detected monotonic timestamps, converting\n");
             /* microseconds instead of seconds, MHz instead of Hz */
             s->timefilter = ff_timefilter_new(1, period, 1.0E-6);
             if (!s->timefilter)
                 return AVERROR(ENOMEM);
             s->ts_mode = V4L_TS_CONVERT_READY;
             return 0;
         }

     }
 #endif
     av_log(ctx, AV_LOG_ERROR, "Unknown timestamps\n");
     return AVERROR(EIO);
 }
 
 static int convert_timestamp(AVFormatContext *ctx, int64_t *ts)
 {
     struct video_data *s = ctx->priv_data;
 
     if (s->ts_mode) {
         int r = init_convert_timestamp(ctx, *ts);
         if (r < 0)
             return r;
     }
 #if HAVE_CLOCK_GETTIME && defined(CLOCK_MONOTONIC)
     if (s->timefilter) {
         int64_t nowa = av_gettime();
         int64_t nowm = av_gettime_monotonic();
         ff_timefilter_update(s->timefilter, nowa, nowm - s->last_time_m);
         s->last_time_m = nowm;
         *ts = ff_timefilter_eval(s->timefilter, *ts - nowm);
     }
 #endif
     return 0;
 }
 

 static int mmap_read_frame(AVFormatContext *ctx, AVPacket *pkt)

 {

     struct video_data *s = ctx->priv_data;

     struct v4l2_buffer buf = {
         .type   = V4L2_BUF_TYPE_VIDEO_CAPTURE,
         .memory = V4L2_MEMORY_MMAP
     };

     struct timeval buf_ts;

     int res;
 

     pkt->size = 0;
 

     /* FIXME: Some special treatment might be needed in case of loss of signal... */

     while ((res = v4l2_ioctl(s->fd, VIDIOC_DQBUF, &buf)) < 0 && (errno == EINTR));

     if (res < 0) {

         if (errno == EAGAIN)

             return AVERROR(EAGAIN);

         res = AVERROR(errno);

         av_log(ctx, AV_LOG_ERROR, "ioctl(VIDIOC_DQBUF): %s\n",

                av_err2str(res));

         return res;

     }

     buf_ts = buf.timestamp;
 

     if (buf.index >= s->buffers) {
         av_log(ctx, AV_LOG_ERROR, "Invalid buffer index received.\n");
         return AVERROR(EINVAL);
     }

     atomic_fetch_add(&s->buffers_queued, -1);

     // always keep at least one buffer queued

     av_assert0(atomic_load(&s->buffers_queued) >= 1);

 #ifdef V4L2_BUF_FLAG_ERROR

     if (buf.flags & V4L2_BUF_FLAG_ERROR) {
         av_log(ctx, AV_LOG_WARNING,
                "Dequeued v4l2 buffer contains corrupted data (%d bytes).\n",
                buf.bytesused);
         buf.bytesused = 0;

     } else
 #endif
     {

         /* CPIA is a compressed format and we don't know the exact number of bytes
          * used by a frame, so set it here as the driver announces it. */
         if (ctx->video_codec_id == AV_CODEC_ID_CPIA)
             s->frame_size = buf.bytesused;

         if (s->frame_size > 0 && buf.bytesused != s->frame_size) {
             av_log(ctx, AV_LOG_ERROR,
                    "Dequeued v4l2 buffer contains %d bytes, but %d were expected. Flags: 0x%08X.\n",
                    buf.bytesused, s->frame_size, buf.flags);
             enqueue_buffer(s, &buf);
             return AVERROR_INVALIDDATA;
         }

     }
 

     /* Image is at s->buff_start[buf.index] */

     if (atomic_load(&s->buffers_queued) == FFMAX(s->buffers / 8, 1)) {

         /* when we start getting low on queued buffers, fall back on copying data */

         res = av_new_packet(pkt, buf.bytesused);
         if (res < 0) {
             av_log(ctx, AV_LOG_ERROR, "Error allocating a packet.\n");

             enqueue_buffer(s, &buf);

             return res;
         }
         memcpy(pkt->data, s->buf_start[buf.index], buf.bytesused);

         res = enqueue_buffer(s, &buf);
         if (res) {

             av_packet_unref(pkt);

             return res;

         }

     } else {

         struct buff_data *buf_descriptor;

         pkt->data     = s->buf_start[buf.index];
         pkt->size     = buf.bytesused;
 
         buf_descriptor = av_malloc(sizeof(struct buff_data));

         if (!buf_descriptor) {

             /* Something went wrong... Since av_malloc() failed, we cannot even
              * allocate a buffer for memcpying into it
              */
             av_log(ctx, AV_LOG_ERROR, "Failed to allocate a buffer descriptor\n");

             enqueue_buffer(s, &buf);

 
             return AVERROR(ENOMEM);
         }

         buf_descriptor->index = buf.index;

         buf_descriptor->s     = s;
 
         pkt->buf = av_buffer_create(pkt->data, pkt->size, mmap_release_buffer,
                                     buf_descriptor, 0);
         if (!pkt->buf) {

             av_log(ctx, AV_LOG_ERROR, "Failed to create a buffer\n");

             enqueue_buffer(s, &buf);

             av_freep(&buf_descriptor);
             return AVERROR(ENOMEM);
         }

     }

     pkt->pts = buf_ts.tv_sec * INT64_C(1000000) + buf_ts.tv_usec;

     convert_timestamp(ctx, &pkt->pts);

     return pkt->size;

 }
 

 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 = {
             .type   = V4L2_BUF_TYPE_VIDEO_CAPTURE,
             .index  = i,
             .memory = V4L2_MEMORY_MMAP
         };

         if (v4l2_ioctl(s->fd, VIDIOC_QBUF, &buf) < 0) {
             res = AVERROR(errno);

             av_log(ctx, AV_LOG_ERROR, "ioctl(VIDIOC_QBUF): %s\n",

                    av_err2str(res));

             return res;

         }
     }

     atomic_store(&s->buffers_queued, s->buffers);

 
     type = V4L2_BUF_TYPE_VIDEO_CAPTURE;

     if (v4l2_ioctl(s->fd, VIDIOC_STREAMON, &type) < 0) {
         res = AVERROR(errno);

         av_log(ctx, AV_LOG_ERROR, "ioctl(VIDIOC_STREAMON): %s\n",

                av_err2str(res));

         return res;

     }
 
     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...
      */

     v4l2_ioctl(s->fd, VIDIOC_STREAMOFF, &type);

     for (i = 0; i < s->buffers; i++) {

         v4l2_munmap(s->buf_start[i], s->buf_len[i]);

     }

     av_freep(&s->buf_start);
     av_freep(&s->buf_len);

 }
 

 static int v4l2_set_parameters(AVFormatContext *ctx)

 {

     struct video_data *s = ctx->priv_data;

     struct v4l2_standard standard = { 0 };

     struct v4l2_streamparm streamparm = { 0 };

     struct v4l2_fract *tpf;

     AVRational framerate_q = { 0 };

     int i, ret;

     if (s->framerate &&
         (ret = av_parse_video_rate(&framerate_q, s->framerate)) < 0) {

         av_log(ctx, AV_LOG_ERROR, "Could not parse framerate '%s'.\n",

                s->framerate);

         return ret;
     }

     if (s->standard) {

         if (s->std_id) {

             ret = 0;

             av_log(ctx, AV_LOG_DEBUG, "Setting standard: %s\n", s->standard);

             /* set tv standard */
             for (i = 0; ; i++) {
                 standard.index = i;

                 if (v4l2_ioctl(s->fd, VIDIOC_ENUMSTD, &standard) < 0) {

                     ret = AVERROR(errno);

                     break;
                 }
                 if (!av_strcasecmp(standard.name, s->standard))

                     break;
             }
             if (ret < 0) {

                 av_log(ctx, AV_LOG_ERROR, "Unknown or unsupported standard '%s'\n", s->standard);

                 return ret;

             }
 
             if (v4l2_ioctl(s->fd, VIDIOC_S_STD, &standard.id) < 0) {

                 ret = AVERROR(errno);

                 av_log(ctx, AV_LOG_ERROR, "ioctl(VIDIOC_S_STD): %s\n", av_err2str(ret));

                 return ret;

             }
         } else {

             av_log(ctx, AV_LOG_WARNING,

                    "This device does not support any standard\n");
         }
     }
 
     /* get standard */
     if (v4l2_ioctl(s->fd, VIDIOC_G_STD, &s->std_id) == 0) {
         tpf = &standard.frameperiod;
         for (i = 0; ; i++) {

             standard.index = i;

             if (v4l2_ioctl(s->fd, VIDIOC_ENUMSTD, &standard) < 0) {
                 ret = AVERROR(errno);

                 if (ret == AVERROR(EINVAL)
 #ifdef ENODATA
                     || ret == AVERROR(ENODATA)
 #endif
                 ) {

                     tpf = &streamparm.parm.capture.timeperframe;
                     break;
                 }

                 av_log(ctx, AV_LOG_ERROR, "ioctl(VIDIOC_ENUMSTD): %s\n", av_err2str(ret));

                 return ret;

             }
             if (standard.id == s->std_id) {

                 av_log(ctx, AV_LOG_DEBUG,

                        "Current standard: %s, id: %"PRIx64", frameperiod: %d/%d\n",

                        standard.name, (uint64_t)standard.id, tpf->numerator, tpf->denominator);

                 break;

             }

         }

     } else {
         tpf = &streamparm.parm.capture.timeperframe;
     }

     streamparm.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
     if (v4l2_ioctl(s->fd, VIDIOC_G_PARM, &streamparm) < 0) {

         ret = AVERROR(errno);

         av_log(ctx, AV_LOG_WARNING, "ioctl(VIDIOC_G_PARM): %s\n", av_err2str(ret));
     } else if (framerate_q.num && framerate_q.den) {

         if (streamparm.parm.capture.capability & V4L2_CAP_TIMEPERFRAME) {
             tpf = &streamparm.parm.capture.timeperframe;
 

             av_log(ctx, AV_LOG_DEBUG, "Setting time per frame to %d/%d\n",

                    framerate_q.den, framerate_q.num);

             tpf->numerator   = framerate_q.den;
             tpf->denominator = framerate_q.num;

             if (v4l2_ioctl(s->fd, VIDIOC_S_PARM, &streamparm) < 0) {

                 ret = AVERROR(errno);

                 av_log(ctx, AV_LOG_ERROR, "ioctl(VIDIOC_S_PARM): %s\n",
                        av_err2str(ret));

                 return ret;

             }
 
             if (framerate_q.num != tpf->denominator ||
                 framerate_q.den != tpf->numerator) {

                 av_log(ctx, AV_LOG_INFO,

                        "The driver changed the time per frame from "
                        "%d/%d to %d/%d\n",
                        framerate_q.den, framerate_q.num,
                        tpf->numerator, tpf->denominator);
             }
         } else {

             av_log(ctx, AV_LOG_WARNING,

                    "The driver does not permit changing the time per frame\n");

         }

     }

     if (tpf->denominator > 0 && tpf->numerator > 0) {

         ctx->streams[0]->avg_frame_rate.num = tpf->denominator;
         ctx->streams[0]->avg_frame_rate.den = tpf->numerator;
         ctx->streams[0]->r_frame_rate = ctx->streams[0]->avg_frame_rate;

     } else

         av_log(ctx, AV_LOG_WARNING, "Time per frame unknown\n");

     return 0;
 }
 

 static int device_try_init(AVFormatContext *ctx,

                            enum AVPixelFormat pix_fmt,
                            int *width,
                            int *height,
                            uint32_t *desired_format,
                            enum AVCodecID *codec_id)

 {

     int ret, i;

     *desired_format = ff_fmt_ff2v4l(pix_fmt, ctx->video_codec_id);

     if (*desired_format) {

         ret = device_init(ctx, width, height, *desired_format);

         if (ret < 0) {
             *desired_format = 0;
             if (ret != AVERROR(EINVAL))
                 return ret;
         }
     }
 
     if (!*desired_format) {

         for (i = 0; ff_fmt_conversion_table[i].codec_id != AV_CODEC_ID_NONE; i++) {

             if (ctx->video_codec_id == AV_CODEC_ID_NONE ||

                 ff_fmt_conversion_table[i].codec_id == ctx->video_codec_id) {

                 av_log(ctx, AV_LOG_DEBUG, "Trying to set codec:%s pix_fmt:%s\n",

                        avcodec_get_name(ff_fmt_conversion_table[i].codec_id),
                        (char *)av_x_if_null(av_get_pix_fmt_name(ff_fmt_conversion_table[i].ff_fmt), "none"));

                 *desired_format = ff_fmt_conversion_table[i].v4l2_fmt;

                 ret = device_init(ctx, width, height, *desired_format);

                 if (ret >= 0)

                     break;

                 else if (ret != AVERROR(EINVAL))
                     return ret;
                 *desired_format = 0;

             }
         }

         if (*desired_format == 0) {

             av_log(ctx, AV_LOG_ERROR, "Cannot find a proper format for "

                    "codec '%s' (id %d), pixel format '%s' (id %d)\n",

                    avcodec_get_name(ctx->video_codec_id), ctx->video_codec_id,

                    (char *)av_x_if_null(av_get_pix_fmt_name(pix_fmt), "none"), pix_fmt);
             ret = AVERROR(EINVAL);
         }

     }
 

     *codec_id = ff_fmt_v4l2codec(*desired_format);

     av_assert0(*codec_id != AV_CODEC_ID_NONE);
     return ret;

 }
 

 static int v4l2_read_probe(AVProbeData *p)
 {
     if (av_strstart(p->filename, "/dev/video", NULL))
         return AVPROBE_SCORE_MAX - 1;
     return 0;
 }
 

 static int v4l2_read_header(AVFormatContext *ctx)

 {

     struct video_data *s = ctx->priv_data;

     AVStream *st;

     int res = 0;

     uint32_t desired_format;

     enum AVCodecID codec_id = AV_CODEC_ID_NONE;

     enum AVPixelFormat pix_fmt = AV_PIX_FMT_NONE;

     struct v4l2_input input = { 0 };

     st = avformat_new_stream(ctx, NULL);

     if (!st)
         return AVERROR(ENOMEM);

 #if CONFIG_LIBV4L2
     /* silence libv4l2 logging. if fopen() fails v4l2_log_file will be NULL
        and errors will get sent to stderr */

     if (s->use_libv4l2)
         v4l2_log_file = fopen("/dev/null", "w");

 #endif
 

     s->fd = device_open(ctx);

     if (s->fd < 0)
         return s->fd;

     if (s->channel != -1) {
         /* set video input */

         av_log(ctx, AV_LOG_DEBUG, "Selecting input_channel: %d\n", s->channel);

         if (v4l2_ioctl(s->fd, VIDIOC_S_INPUT, &s->channel) < 0) {
             res = AVERROR(errno);

             av_log(ctx, AV_LOG_ERROR, "ioctl(VIDIOC_S_INPUT): %s\n", av_err2str(res));

             goto fail;

         }
     } else {
         /* get current video input */
         if (v4l2_ioctl(s->fd, VIDIOC_G_INPUT, &s->channel) < 0) {
             res = AVERROR(errno);

             av_log(ctx, AV_LOG_ERROR, "ioctl(VIDIOC_G_INPUT): %s\n", av_err2str(res));

             goto fail;

         }

     }
 

     /* enum input */

     input.index = s->channel;
     if (v4l2_ioctl(s->fd, VIDIOC_ENUMINPUT, &input) < 0) {

         res = AVERROR(errno);

         av_log(ctx, AV_LOG_ERROR, "ioctl(VIDIOC_ENUMINPUT): %s\n", av_err2str(res));

         goto fail;

     }
     s->std_id = input.std;

     av_log(ctx, AV_LOG_DEBUG, "Current input_channel: %d, input_name: %s, input_std: %"PRIx64"\n",

            s->channel, input.name, (uint64_t)input.std);

     if (s->list_format) {

         list_formats(ctx, s->list_format);

         res = AVERROR_EXIT;
         goto fail;

     }

     if (s->list_standard) {

         list_standards(ctx);

         res = AVERROR_EXIT;
         goto fail;

     }
 

     avpriv_set_pts_info(st, 64, 1, 1000000); /* 64 bits pts in us */

     if (s->pixel_format) {

         const AVCodecDescriptor *desc = avcodec_descriptor_get_by_name(s->pixel_format);

         if (desc)
             ctx->video_codec_id = desc->id;

 
         pix_fmt = av_get_pix_fmt(s->pixel_format);
 

         if (pix_fmt == AV_PIX_FMT_NONE && !desc) {

             av_log(ctx, AV_LOG_ERROR, "No such input format: %s.\n",

                    s->pixel_format);
 

             res = AVERROR(EINVAL);
             goto fail;

         }

     }

     if (!s->width && !s->height) {

         struct v4l2_format fmt = { .type = V4L2_BUF_TYPE_VIDEO_CAPTURE };

         av_log(ctx, AV_LOG_VERBOSE,

                "Querying the device for the current frame size\n");

         if (v4l2_ioctl(s->fd, VIDIOC_G_FMT, &fmt) < 0) {

             res = AVERROR(errno);

             av_log(ctx, AV_LOG_ERROR, "ioctl(VIDIOC_G_FMT): %s\n",
                    av_err2str(res));

             goto fail;

         }

         s->width  = fmt.fmt.pix.width;
         s->height = fmt.fmt.pix.height;

         av_log(ctx, AV_LOG_VERBOSE,

                "Setting frame size to %dx%d\n", s->width, s->height);

     }
 

     res = device_try_init(ctx, pix_fmt, &s->width, &s->height, &desired_format, &codec_id);

     if (res < 0)
         goto fail;

 
     /* If no pixel_format was specified, the codec_id was not known up
      * until now. Set video_codec_id in the context, as codec_id will
      * not be available outside this function
      */

     if (codec_id != AV_CODEC_ID_NONE && ctx->video_codec_id == AV_CODEC_ID_NONE)
         ctx->video_codec_id = codec_id;

     if ((res = av_image_check_size(s->width, s->height, 0, ctx)) < 0)

         goto fail;

     s->pixelformat = desired_format;

     if ((res = v4l2_set_parameters(ctx)) < 0)
         goto fail;
 

     st->codecpar->format = ff_fmt_v4l2ff(desired_format, codec_id);

     if (st->codecpar->format != AV_PIX_FMT_NONE)

         s->frame_size = av_image_get_buffer_size(st->codecpar->format,
                                                  s->width, s->height, 1);

     if ((res = mmap_init(ctx)) ||
         (res = mmap_start(ctx)) < 0)

             goto fail;

     s->top_field_first = first_field(s);

     st->codecpar->codec_type = AVMEDIA_TYPE_VIDEO;
     st->codecpar->codec_id = codec_id;

     if (codec_id == AV_CODEC_ID_RAWVIDEO)

         st->codecpar->codec_tag =
             avcodec_pix_fmt_to_codec_tag(st->codecpar->format);

     else if (codec_id == AV_CODEC_ID_H264) {

         st->need_parsing = AVSTREAM_PARSE_FULL_ONCE;

     }

     if (desired_format == V4L2_PIX_FMT_YVU420)

         st->codecpar->codec_tag = MKTAG('Y', 'V', '1', '2');

     else if (desired_format == V4L2_PIX_FMT_YVU410)

         st->codecpar->codec_tag = MKTAG('Y', 'V', 'U', '9');

     st->codecpar->width = s->width;
     st->codecpar->height = s->height;

     if (st->avg_frame_rate.den)

         st->codecpar->bit_rate = s->frame_size * av_q2d(st->avg_frame_rate) * 8;

     return 0;

 
 fail:
     v4l2_close(s->fd);
     return res;

 }
 

 static int v4l2_read_packet(AVFormatContext *ctx, AVPacket *pkt)

 {

 #if FF_API_CODED_FRAME && FF_API_LAVF_AVCTX

 FF_DISABLE_DEPRECATION_WARNINGS

     struct video_data *s = ctx->priv_data;

     AVFrame *frame = ctx->streams[0]->codec->coded_frame;

 FF_ENABLE_DEPRECATION_WARNINGS
 #endif

     int res;
 

     if ((res = mmap_read_frame(ctx, pkt)) < 0) {

         return res;

     }
 

 #if FF_API_CODED_FRAME && FF_API_LAVF_AVCTX

 FF_DISABLE_DEPRECATION_WARNINGS

     if (frame && s->interlaced) {
         frame->interlaced_frame = 1;
         frame->top_field_first = s->top_field_first;

     }

 FF_ENABLE_DEPRECATION_WARNINGS
 #endif

     return pkt->size;

 }
 

 static int v4l2_read_close(AVFormatContext *ctx)

 {

     struct video_data *s = ctx->priv_data;

     if (atomic_load(&s->buffers_queued) != s->buffers)

         av_log(ctx, AV_LOG_WARNING, "Some buffers are still owned by the caller on "

                "close.\n");
 

     mmap_close(s);

     v4l2_close(s->fd);

     return 0;
 }
 

 static int v4l2_is_v4l_dev(const char *name)
 {
     return !strncmp(name, "video", 5) ||
            !strncmp(name, "radio", 5) ||
            !strncmp(name, "vbi", 3) ||
            !strncmp(name, "v4l-subdev", 10);
 }
 
 static int v4l2_get_device_list(AVFormatContext *ctx, AVDeviceInfoList *device_list)
 {
     struct video_data *s = ctx->priv_data;
     DIR *dir;
     struct dirent *entry;
     AVDeviceInfo *device = NULL;
     struct v4l2_capability cap;
     int ret = 0;
 
     if (!device_list)
         return AVERROR(EINVAL);
 
     dir = opendir("/dev");
     if (!dir) {
         ret = AVERROR(errno);
         av_log(ctx, AV_LOG_ERROR, "Couldn't open the directory: %s\n", av_err2str(ret));
         return ret;
     }
     while ((entry = readdir(dir))) {
         if (!v4l2_is_v4l_dev(entry->d_name))
             continue;
 
         snprintf(ctx->filename, sizeof(ctx->filename), "/dev/%s", entry->d_name);
         if ((s->fd = device_open(ctx)) < 0)
             continue;
 
         if (v4l2_ioctl(s->fd, VIDIOC_QUERYCAP, &cap) < 0) {
             ret = AVERROR(errno);
             av_log(ctx, AV_LOG_ERROR, "ioctl(VIDIOC_QUERYCAP): %s\n", av_err2str(ret));
             goto fail;
         }
 
         device = av_mallocz(sizeof(AVDeviceInfo));
         if (!device) {
             ret = AVERROR(ENOMEM);
             goto fail;
         }
         device->device_name = av_strdup(ctx->filename);
         device->device_description = av_strdup(cap.card);
         if (!device->device_name || !device->device_description) {
             ret = AVERROR(ENOMEM);
             goto fail;
         }
 
         if ((ret = av_dynarray_add_nofree(&device_list->devices,
                                           &device_list->nb_devices, device)) < 0)
             goto fail;
 
         v4l2_close(s->fd);
         s->fd = -1;
         continue;
 
       fail:
         if (device) {
             av_freep(&device->device_name);
             av_freep(&device->device_description);
             av_freep(&device);
         }
         if (s->fd >= 0)
             v4l2_close(s->fd);
         s->fd = -1;
         break;
     }
     closedir(dir);
     return ret;
 }
 

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

 static const AVOption options[] = {

     { "standard",     "set TV standard, used only by analog frame grabber",       OFFSET(standard),     AV_OPT_TYPE_STRING, {.str = NULL }, 0, 0,       DEC },

     { "channel",      "set TV channel, used only by frame grabber",               OFFSET(channel),      AV_OPT_TYPE_INT,    {.i64 = -1 },  -1, INT_MAX, DEC },

     { "video_size",   "set frame size",                                           OFFSET(width),        AV_OPT_TYPE_IMAGE_SIZE, {.str = NULL},  0, 0,   DEC },
     { "pixel_format", "set preferred pixel format",                               OFFSET(pixel_format), AV_OPT_TYPE_STRING, {.str = NULL},  0, 0,       DEC },
     { "input_format", "set preferred pixel format (for raw video) or codec name", OFFSET(pixel_format), AV_OPT_TYPE_STRING, {.str = NULL},  0, 0,       DEC },
     { "framerate",    "set frame rate",                                           OFFSET(framerate),    AV_OPT_TYPE_STRING, {.str = NULL},  0, 0,       DEC },
 
     { "list_formats", "list available formats and exit",                          OFFSET(list_format),  AV_OPT_TYPE_INT,    {.i64 = 0 },  0, INT_MAX, DEC, "list_formats" },
     { "all",          "show all available formats",                               OFFSET(list_format),  AV_OPT_TYPE_CONST,  {.i64 = V4L_ALLFORMATS  },    0, INT_MAX, DEC, "list_formats" },
     { "raw",          "show only non-compressed formats",                         OFFSET(list_format),  AV_OPT_TYPE_CONST,  {.i64 = V4L_RAWFORMATS  },    0, INT_MAX, DEC, "list_formats" },
     { "compressed",   "show only compressed formats",                             OFFSET(list_format),  AV_OPT_TYPE_CONST,  {.i64 = V4L_COMPFORMATS },    0, INT_MAX, DEC, "list_formats" },
 

     { "list_standards", "list supported standards and exit",                      OFFSET(list_standard), AV_OPT_TYPE_INT,   {.i64 = 0 },  0, 1, DEC, "list_standards" },
     { "all",            "show all supported standards",                           OFFSET(list_standard), AV_OPT_TYPE_CONST, {.i64 = 1 },  0, 0, DEC, "list_standards" },
 

     { "timestamps",   "set type of timestamps for grabbed frames",                OFFSET(ts_mode),      AV_OPT_TYPE_INT,    {.i64 = 0 }, 0, 2, DEC, "timestamps" },
     { "ts",           "set type of timestamps for grabbed frames",                OFFSET(ts_mode),      AV_OPT_TYPE_INT,    {.i64 = 0 }, 0, 2, DEC, "timestamps" },
     { "default",      "use timestamps from the kernel",                           OFFSET(ts_mode),      AV_OPT_TYPE_CONST,  {.i64 = V4L_TS_DEFAULT  }, 0, 2, DEC, "timestamps" },
     { "abs",          "use absolute timestamps (wall clock)",                     OFFSET(ts_mode),      AV_OPT_TYPE_CONST,  {.i64 = V4L_TS_ABS      }, 0, 2, DEC, "timestamps" },
     { "mono2abs",     "force conversion from monotonic to absolute timestamps",   OFFSET(ts_mode),      AV_OPT_TYPE_CONST,  {.i64 = V4L_TS_MONO2ABS }, 0, 2, DEC, "timestamps" },

     { "use_libv4l2",  "use libv4l2 (v4l-utils) conversion functions",             OFFSET(use_libv4l2),  AV_OPT_TYPE_BOOL,   {.i64 = 0}, 0, 1, DEC },

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

     .category   = AV_CLASS_CATEGORY_DEVICE_VIDEO_INPUT,

 };
 

 AVInputFormat ff_v4l2_demuxer = {

     .name           = "video4linux2,v4l2",

     .long_name      = NULL_IF_CONFIG_SMALL("Video4Linux2 device grab"),
     .priv_data_size = sizeof(struct video_data),

     .read_probe     = v4l2_read_probe,

     .read_header    = v4l2_read_header,
     .read_packet    = v4l2_read_packet,
     .read_close     = v4l2_read_close,

     .get_device_list = v4l2_get_device_list,

     .flags          = AVFMT_NOFILE,
     .priv_class     = &v4l2_class,

 };