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* Video4Linux2 grab interface
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* Copyright (c) 2000,2001 Fabrice Bellard.
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* Copyright (c) 2006 Luca Abeni.
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* Part of this file is based on the V4L2 video capture example
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* (http://v4l2spec.bytesex.org/v4l2spec/capture.c)
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* Thanks to Michael Niedermayer for providing the mapping between
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* V4L2_PIX_FMT_* and PIX_FMT_*
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* This file is part of FFmpeg.
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* FFmpeg is free software; you can redistribute it and/or
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* modify it under the terms of the GNU Lesser General Public
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* License as published by the Free Software Foundation; either
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* version 2.1 of the License, or (at your option) any later version.
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* FFmpeg is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* Lesser General Public License for more details.
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* You should have received a copy of the GNU Lesser General Public
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* License along with FFmpeg; if not, write to the Free Software
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* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
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#include <sys/ioctl.h>
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#include <asm/types.h>
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#include <linux/videodev2.h>
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static const int desired_video_buffers = 256;
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int frame_format; /* V4L2_PIX_FMT_* */
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enum io_method io_method;
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unsigned int *buf_len;
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enum PixelFormat ff_fmt;
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static struct fmt_map fmt_conversion_table[] = {
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.ff_fmt = PIX_FMT_YUV420P,
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.v4l2_fmt = V4L2_PIX_FMT_YUV420,
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.ff_fmt = PIX_FMT_YUV422P,
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.v4l2_fmt = V4L2_PIX_FMT_YUV422P,
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.ff_fmt = PIX_FMT_YUYV422,
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.v4l2_fmt = V4L2_PIX_FMT_YUYV,
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.ff_fmt = PIX_FMT_UYVY422,
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.v4l2_fmt = V4L2_PIX_FMT_UYVY,
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.ff_fmt = PIX_FMT_YUV411P,
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.v4l2_fmt = V4L2_PIX_FMT_YUV411P,
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.ff_fmt = PIX_FMT_YUV410P,
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.v4l2_fmt = V4L2_PIX_FMT_YUV410,
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.ff_fmt = PIX_FMT_BGR24,
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.v4l2_fmt = V4L2_PIX_FMT_BGR24,
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.ff_fmt = PIX_FMT_RGB24,
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.v4l2_fmt = V4L2_PIX_FMT_RGB24,
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.ff_fmt = PIX_FMT_RGB32,
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.v4l2_fmt = V4L2_PIX_FMT_BGR32,
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.ff_fmt = PIX_FMT_GRAY8,
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.v4l2_fmt = V4L2_PIX_FMT_GREY,
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static int device_open(AVFormatContext *ctx, uint32_t *capabilities)
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struct v4l2_capability cap;
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if (ctx->flags & AVFMT_FLAG_NONBLOCK) {
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fd = open(ctx->filename, flags, 0);
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av_log(ctx, AV_LOG_ERROR, "Cannot open video device %s : %s\n",
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ctx->filename, strerror(errno));
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res = ioctl(fd, VIDIOC_QUERYCAP, &cap);
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// ENOIOCTLCMD definition only availble on __KERNEL__
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if (res < 0 && errno == 515)
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av_log(ctx, AV_LOG_ERROR, "QUERYCAP not implemented, probably V4L device but not supporting V4L2\n");
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av_log(ctx, AV_LOG_ERROR, "ioctl(VIDIOC_QUERYCAP): %s\n",
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if ((cap.capabilities & V4L2_CAP_VIDEO_CAPTURE) == 0) {
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av_log(ctx, AV_LOG_ERROR, "Not a video capture device\n");
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*capabilities = cap.capabilities;
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static int device_init(AVFormatContext *ctx, int *width, int *height, int pix_fmt)
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struct video_data *s = ctx->priv_data;
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struct v4l2_format fmt;
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memset(&fmt, 0, sizeof(struct v4l2_format));
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fmt.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
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fmt.fmt.pix.width = *width;
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fmt.fmt.pix.height = *height;
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fmt.fmt.pix.pixelformat = pix_fmt;
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fmt.fmt.pix.field = V4L2_FIELD_INTERLACED;
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res = ioctl(fd, VIDIOC_S_FMT, &fmt);
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if ((*width != fmt.fmt.pix.width) || (*height != fmt.fmt.pix.height)) {
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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);
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*width = fmt.fmt.pix.width;
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*height = fmt.fmt.pix.height;
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static int first_field(int fd)
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res = ioctl(fd, VIDIOC_G_STD, &std);
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if (std & V4L2_STD_NTSC) {
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static uint32_t fmt_ff2v4l(enum PixelFormat pix_fmt)
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for (i = 0; i < sizeof(fmt_conversion_table) / sizeof(struct fmt_map); i++) {
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if (fmt_conversion_table[i].ff_fmt == pix_fmt) {
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return fmt_conversion_table[i].v4l2_fmt;
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static enum PixelFormat fmt_v4l2ff(uint32_t pix_fmt)
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for (i = 0; i < sizeof(fmt_conversion_table) / sizeof(struct fmt_map); i++) {
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if (fmt_conversion_table[i].v4l2_fmt == pix_fmt) {
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return fmt_conversion_table[i].ff_fmt;
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static int mmap_init(AVFormatContext *ctx)
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struct video_data *s = ctx->priv_data;
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struct v4l2_requestbuffers req;
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memset(&req, 0, sizeof(struct v4l2_requestbuffers));
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req.count = desired_video_buffers;
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req.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
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req.memory = V4L2_MEMORY_MMAP;
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res = ioctl (s->fd, VIDIOC_REQBUFS, &req);
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if (errno == EINVAL) {
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av_log(ctx, AV_LOG_ERROR, "Device does not support mmap\n");
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av_log(ctx, AV_LOG_ERROR, "ioctl(VIDIOC_REQBUFS)\n");
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av_log(ctx, AV_LOG_ERROR, "Insufficient buffer memory\n");
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s->buffers = req.count;
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s->buf_start = av_malloc(sizeof(void *) * s->buffers);
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if (s->buf_start == NULL) {
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av_log(ctx, AV_LOG_ERROR, "Cannot allocate buffer pointers\n");
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s->buf_len = av_malloc(sizeof(unsigned int) * s->buffers);
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if (s->buf_len == NULL) {
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av_log(ctx, AV_LOG_ERROR, "Cannot allocate buffer sizes\n");
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av_free(s->buf_start);
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for (i = 0; i < req.count; i++) {
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struct v4l2_buffer buf;
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memset(&buf, 0, sizeof(struct v4l2_buffer));
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buf.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
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buf.memory = V4L2_MEMORY_MMAP;
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res = ioctl (s->fd, VIDIOC_QUERYBUF, &buf);
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av_log(ctx, AV_LOG_ERROR, "ioctl(VIDIOC_QUERYBUF)\n");
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s->buf_len[i] = buf.length;
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if (s->buf_len[i] < s->frame_size) {
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av_log(ctx, AV_LOG_ERROR, "Buffer len [%d] = %d != %d\n", i, s->buf_len[i], s->frame_size);
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s->buf_start[i] = mmap (NULL, buf.length,
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PROT_READ | PROT_WRITE, MAP_SHARED, s->fd, buf.m.offset);
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if (s->buf_start[i] == MAP_FAILED) {
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av_log(ctx, AV_LOG_ERROR, "mmap: %s\n", strerror(errno));
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static int read_init(AVFormatContext *ctx)
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static void mmap_release_buffer(AVPacket *pkt)
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struct v4l2_buffer buf;
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struct buff_data *buf_descriptor = pkt->priv;
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memset(&buf, 0, sizeof(struct v4l2_buffer));
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buf.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
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buf.memory = V4L2_MEMORY_MMAP;
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buf.index = buf_descriptor->index;
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fd = buf_descriptor->fd;
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av_free(buf_descriptor);
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res = ioctl (fd, VIDIOC_QBUF, &buf);
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av_log(NULL, AV_LOG_ERROR, "ioctl(VIDIOC_QBUF)\n");
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static int mmap_read_frame(AVFormatContext *ctx, AVPacket *pkt)
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struct video_data *s = ctx->priv_data;
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struct v4l2_buffer buf;
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struct buff_data *buf_descriptor;
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memset(&buf, 0, sizeof(struct v4l2_buffer));
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buf.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
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buf.memory = V4L2_MEMORY_MMAP;
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/* FIXME: Some special treatment might be needed in case of loss of signal... */
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while ((res = ioctl(s->fd, VIDIOC_DQBUF, &buf)) < 0 && (errno == EINTR));
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if (errno == EAGAIN) {
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return AVERROR(EAGAIN);
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av_log(ctx, AV_LOG_ERROR, "ioctl(VIDIOC_DQBUF): %s\n", strerror(errno));
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assert (buf.index < s->buffers);
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if (buf.bytesused != s->frame_size) {
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av_log(ctx, AV_LOG_ERROR, "The v4l2 frame is %d bytes, but %d bytes are expected\n", buf.bytesused, s->frame_size);
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/* Image is at s->buff_start[buf.index] */
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pkt->data= s->buf_start[buf.index];
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pkt->size = buf.bytesused;
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pkt->pts = buf.timestamp.tv_sec * INT64_C(1000000) + buf.timestamp.tv_usec;
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pkt->destruct = mmap_release_buffer;
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buf_descriptor = av_malloc(sizeof(struct buff_data));
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if (buf_descriptor == NULL) {
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/* Something went wrong... Since av_malloc() failed, we cannot even
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* allocate a buffer for memcopying into it
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av_log(ctx, AV_LOG_ERROR, "Failed to allocate a buffer descriptor\n");
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res = ioctl (s->fd, VIDIOC_QBUF, &buf);
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buf_descriptor->fd = s->fd;
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buf_descriptor->index = buf.index;
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pkt->priv = buf_descriptor;
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return s->buf_len[buf.index];
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static int read_frame(AVFormatContext *ctx, AVPacket *pkt)
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static int mmap_start(AVFormatContext *ctx)
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struct video_data *s = ctx->priv_data;
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enum v4l2_buf_type type;
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for (i = 0; i < s->buffers; i++) {
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struct v4l2_buffer buf;
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memset(&buf, 0, sizeof(struct v4l2_buffer));
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buf.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
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buf.memory = V4L2_MEMORY_MMAP;
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res = ioctl (s->fd, VIDIOC_QBUF, &buf);
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av_log(ctx, AV_LOG_ERROR, "ioctl(VIDIOC_QBUF): %s\n", strerror(errno));
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type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
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res = ioctl (s->fd, VIDIOC_STREAMON, &type);
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av_log(ctx, AV_LOG_ERROR, "ioctl(VIDIOC_STREAMON): %s\n", strerror(errno));
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static void mmap_close(struct video_data *s)
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enum v4l2_buf_type type;
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type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
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/* We do not check for the result, because we could
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* not do anything about it anyway...
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ioctl(s->fd, VIDIOC_STREAMOFF, &type);
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for (i = 0; i < s->buffers; i++) {
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munmap(s->buf_start[i], s->buf_len[i]);
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av_free(s->buf_start);
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static int v4l2_set_parameters( AVFormatContext *s1, AVFormatParameters *ap )
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struct video_data *s = s1->priv_data;
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struct v4l2_input input;
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struct v4l2_standard standard;
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/* set tv video input */
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memset (&input, 0, sizeof (input));
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input.index = ap->channel;
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if(ioctl (s->fd, VIDIOC_ENUMINPUT, &input) < 0) {
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av_log(s1, AV_LOG_ERROR, "The V4L2 driver ioctl enum input failed:\n");
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av_log(s1, AV_LOG_DEBUG, "The V4L2 driver set input_id: %d, input: %s\n",
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ap->channel, input.name);
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if(ioctl (s->fd, VIDIOC_S_INPUT, &input.index) < 0 ) {
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av_log(s1, AV_LOG_ERROR, "The V4L2 driver ioctl set input(%d) failed\n",
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av_log(s1, AV_LOG_DEBUG, "The V4L2 driver set standard: %s\n",
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/* set tv standard */
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memset (&standard, 0, sizeof (standard));
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if (ioctl(s->fd, VIDIOC_ENUMSTD, &standard) < 0) {
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av_log(s1, AV_LOG_ERROR, "The V4L2 driver ioctl set standard(%s) failed\n",
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if(!strcasecmp(standard.name, ap->standard)) {
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av_log(s1, AV_LOG_DEBUG, "The V4L2 driver set standard: %s, id: %"PRIu64"\n",
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ap->standard, standard.id);
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if (ioctl(s->fd, VIDIOC_S_STD, &standard.id) < 0) {
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av_log(s1, AV_LOG_ERROR, "The V4L2 driver ioctl set standard(%s) failed\n",
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static int v4l2_read_header(AVFormatContext *s1, AVFormatParameters *ap)
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struct video_data *s = s1->priv_data;
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int res, frame_rate, frame_rate_base;
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uint32_t desired_format, capabilities;
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if (ap->width <= 0 || ap->height <= 0 || ap->time_base.den <= 0) {
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av_log(s1, AV_LOG_ERROR, "Missing/Wrong width, height or framerate\n");
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frame_rate = ap->time_base.den;
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frame_rate_base = ap->time_base.num;
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if((unsigned)width > 32767 || (unsigned)height > 32767) {
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av_log(s1, AV_LOG_ERROR, "Wrong size %dx%d\n", width, height);
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st = av_new_stream(s1, 0);
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return AVERROR(ENOMEM);
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av_set_pts_info(st, 64, 1, 1000000); /* 64 bits pts in us */
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s->frame_rate = frame_rate;
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s->frame_rate_base = frame_rate_base;
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s->fd = device_open(s1, &capabilities);
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av_log(s1, AV_LOG_INFO, "[%d]Capabilities: %x\n", s->fd, capabilities);
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desired_format = fmt_ff2v4l(ap->pix_fmt);
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if (desired_format == 0 || (device_init(s1, &width, &height, desired_format) < 0)) {
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desired_format = fmt_conversion_table[i].v4l2_fmt;
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if (device_init(s1, &width, &height, desired_format) < 0) {
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if (i == sizeof(fmt_conversion_table) / sizeof(struct fmt_map)) {
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if (desired_format == 0) {
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av_log(s1, AV_LOG_ERROR, "Cannot find a proper format.\n");
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s->frame_format = desired_format;
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if( v4l2_set_parameters( s1, ap ) < 0 )
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st->codec->pix_fmt = fmt_v4l2ff(desired_format);
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s->frame_size = avpicture_get_size(st->codec->pix_fmt, width, height);
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if (capabilities & V4L2_CAP_STREAMING) {
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s->io_method = io_mmap;
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res = mmap_start(s1);
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s->io_method = io_read;
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s->top_field_first = first_field(s->fd);
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st->codec->codec_type = CODEC_TYPE_VIDEO;
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st->codec->codec_id = CODEC_ID_RAWVIDEO;
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st->codec->width = width;
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st->codec->height = height;
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st->codec->time_base.den = frame_rate;
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st->codec->time_base.num = frame_rate_base;
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st->codec->bit_rate = s->frame_size * 1/av_q2d(st->codec->time_base) * 8;
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static int v4l2_read_packet(AVFormatContext *s1, AVPacket *pkt)
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struct video_data *s = s1->priv_data;
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if (s->io_method == io_mmap) {
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res = mmap_read_frame(s1, pkt);
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} else if (s->io_method == io_read) {
605
if (av_new_packet(pkt, s->frame_size) < 0)
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res = read_frame(s1, pkt);
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if (s1->streams[0]->codec->coded_frame) {
617
s1->streams[0]->codec->coded_frame->interlaced_frame = 1;
618
s1->streams[0]->codec->coded_frame->top_field_first = s->top_field_first;
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return s->frame_size;
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static int v4l2_read_close(AVFormatContext *s1)
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struct video_data *s = s1->priv_data;
628
if (s->io_method == io_mmap) {
636
AVInputFormat v4l2_demuxer = {
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sizeof(struct video_data),
644
.flags = AVFMT_NOFILE,