On Wed, 14 Jul 2004, J�r�mie Knuesel wrote:
> Hello,
>
> How can I skip the first frame in a yuv stream?
>
> I pipe the data from mplayer through y4mscaler to mpeg2enc. The problem
> is that mplayer often puts a plain green frame at the beginning of the
> stream. How can I skip it in the encoding?
Here is a utility that I use to trim yuv4mpeg streams. Link it with
-lmjpegutils and try 'y4mcut -h' for usage.
Selva
/*
* Copyright (C) 2001 Selva Nair <[EMAIL PROTECTED]>
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*
* This program 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 General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
*
*/
/* Build instructions
* gcc -Wall -O2 -DHAVE_STDINT_H -I /usr/local/include/mjpegtools -o y4mcut \
* y4mcut.c -lmjpegutils
*/
#include <stdio.h>
#include <unistd.h>
#include <stdlib.h>
#include <string.h>
#include <mjpegtools/yuv4mpeg.h>
#include <mjpegtools/mjpeg_logging.h>
static void usage(char *name )
{
fprintf(stderr,
"A filter to select specified number of YUV4MPEG\n"
"frames from input stream. Reads input from stdin\n"
"and outputs to stdout as a YUV4MPEG stream.\n"
"Usage: %s: [-h] [-v num] [-s num] [-o num]\n"
" -h - print this help\n"
" -v - verbosity [0..2]\n\n"
" -s num - skip num frames (0)\n"
" -o num - output num frames only -- use\n"
" a negative number for all (-1)\n"
"Author: Selva Nair\n", name);
}
int main(int argc, char *argv[])
{
int verbose = 1;
int nskip = 0;
int nout = -1;
char *prog = "y4mcut";
int i;
int input_fd = 0;
int output_fd = 1;
int c;
int frames_in, frames_out;
int horz, vert;
unsigned char *frame[3];
y4m_stream_info_t istream;
y4m_frame_info_t iframe;
while((c = getopt(argc, argv, "hv:s:o:")) != EOF) {
switch(c) {
case 'v':
verbose = atoi (optarg);
if( verbose < 0 || verbose >2 )
{
usage (argv[0]);
exit (1);
}
(void)mjpeg_default_handler_verbosity(verbose);
break;
case 'h':
usage (argv[0]);
exit(0);
case 's':
if(sscanf(optarg, "%d",
&nskip) != 1) usage(argv[0]);
break;
case 'o':
if(sscanf(optarg, "%d",
&nout) != 1) usage(argv[0]);
break;
default:
exit(0);
}
}
y4m_init_stream_info(&istream);
y4m_init_frame_info(&iframe);
i = y4m_read_stream_header(input_fd, &istream);
i = y4m_write_stream_header(output_fd, &istream);
if (i != Y4M_OK)
mjpeg_error_exit1("Input stream error: %s", y4m_strerr(i));
horz = istream.width;
vert = istream.height;
frame[0] = alloca(horz * vert);
frame[1] = alloca((horz / 2) * (vert / 2));
frame[2] = alloca((horz / 2) * (vert / 2));
frames_in = 0;
frames_out = 0;
while (y4m_read_frame(input_fd, &istream, &iframe, frame) == Y4M_OK) {
frames_in++;
if(frames_in <= nskip) continue;
if (nout < 0 || frames_out < nout ) {
if(y4m_write_frame(output_fd, &istream, &iframe, frame) == Y4M_OK)
frames_out++;
else {
mjpeg_warn("%s: error writing output frame", prog);
break;
}
}
else {
mjpeg_info("%s: Skipped %d frames", prog, nskip);
mjpeg_info("%s: Output %d frames", prog, frames_out);
break;
}
}
if(nout > 0 && frames_out < nout ) mjpeg_warn("%s: not enough frames in input",
prog);
y4m_fini_stream_info(&istream);
y4m_fini_frame_info(&iframe);
exit(0);
}
