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• reading video mpegts stream from stdin using libavformat libavcodec

  1er février 2012, par D Starkweather

  I'm trying to read video frames from stdin using ffmpeg's libav* lib collection. Simply passing "pipe:0" or "pipe :" as the filename to avformat_open_input_file() in my program does not do the trick. (e.g. cat /dev/video0 | ./myprogram OR ./myprogram < /dev/video0 ; it also fails using file.avi in place of /dev/video0).

  Peeking into ffmpeg.c, I find the following bit of code using tcsetattr() to set the termios :

  struct termios tty;
  
  
  
  if (tcgetattr (0, &tty) == 0) {
  
  oldtty = tty;
  
  restore_tty = 1;
  
  atexit(term_exit);
  
  
  
  tty.c_iflag &= ~(IGNBRK|BRKINT|PARMRK|ISTRIP
  
                        |INLCR|IGNCR|ICRNL|IXON);
  
  tty.c_oflag |= OPOST;
  
  tty.c_lflag &= ~(ECHO|ECHONL|ICANON|IEXTEN);
  
  tty.c_cflag &= ~(CSIZE|PARENB);
  
  tty.c_cflag |= CS8;
  
  tty.c_cc[VMIN] = 1;
  
  tty.c_cc[VTIME] = 0;
  
  
  
  tcsetattr (0, TCSANOW, &tty);
  
  }
  
  signal(SIGQUIT, sigterm_handler); /* Quit (POSIX).  */
  
  }
  
  
  
  avformat_network_deinit();
  
  
  
  signal(SIGINT , sigterm_handler); /* Interrupt (ANSI).    */
  
  signal(SIGTERM, sigterm_handler); /* Termination (ANSI).  */
  
  signal(SIGXCPU, sigterm_handler);

  However, when I try this, it appears to have no effect. What settings do I need in the termios struct to continuously read video frames in ?

  Currently, all i am able to do is call av_read_frames a few times (return code 0) before it usually either segfaults or hangs waiting. The buffer usually contains just a blank screen (all black). With any luck, the video buffer will contain the first video frame it comes across, but does not update to the later frames.

  (I'm running this on Debian 6.0) Here's my version of ffmpeg :

  ffmpeg version N-36936-g4cf81d9 Copyright (c) 2000-2012 the FFmpeg
  developers built on Jan 19 2012 20:51:47 with gcc 4.4.5
  configuration : —enable-shared —enable-gray —enable-hardcoded-tables
  —enable-runtime-cpudetect —enable-libmp3lame —enable-libopenjpeg —enable-librtmp —enable-libtheora —enable-libvorbis —enable-libx264 —enable-libxvid —enable-zlib —enable-gpl libavutil 51. 34.101 / 51. 34.101 libavcodec 53. 57.100 /
  53. 57.100 libavformat 53. 30.100 / 53. 30.100 libavdevice 53. 4.100 / 53. 4.100 libavfilter 2. 59.101 / 2. 59.101 libswscale 2. 1.100 / 2. 1.100 libswresample 0. 6.100 /
  0. 6.100 libpostproc 52. 0.100 / 52. 0.100 Hyper fast Audio and Video encoder usage : ffmpeg [options] [[infile options] -i
  infile].

  Thank you very much for any help helpful tips. It is much appreciated.

  D. Grant Starkweather

• Perl FFMpeg print output

  31 janvier 2012, par user346443

  Hi im using the following perl command to convert files with ffmpeg :

  system ("/usr/local/bin/ffmpeg -i $inputFile $outputFile");

  I would like to know if its possible to print the ffmpeg output ?

  Cheers

  UPDATE

  The solution was to use backticks

  my $output = qx{/usr/local/bin/ffmpeg -i $inputFile $outputFile 2>&1};
  
  print $output

  This prints out the following :

  FFmpeg version SVN-r26402, Copyright (c) 2000-2011 the FFmpeg developers built on Jan 31 2012 12:30:35 with gcc 4.4.5 20110214 (Red Hat 4.4.5-6) configuration: --enable-libmp3lame --disable-mmx --enable-shared libavutil 50.36. 0 / 50.36. 0 libavcore 0.16. 1 / 0.16. 1 libavcodec 52.108. 0 / 52.108. 0 libavformat 52.93. 0 / 52.93. 0 libavdevice 52. 2. 3 / 52. 2. 3 libavfilter 1.74. 0 / 1.74. 0 libswscale 0.12. 0 / 0.12. 0 [wav @ 0x8af94c0] max_analyze_duration reached Input #0, wav, from 'a.wav': Duration: 00:00:05.84, bitrate: 1537 kb/s Stream #0.0: Audio: pcm_s16le, 48000 Hz, 2 channels, s16, 1536 kb/s Output #0, mp3, to 'a.mp3': Metadata: TSSE : Lavf52.93.0 Stream #0.0: Audio: libmp3lame, 48000 Hz, 2 channels, s16, 64 kb/s Stream mapping: Stream #0.0 -> #0.0 Press [q] to stop encoding size= 42kB time=5.42 bitrate= 64.0kbits/s size= 46kB time=5.88 bitrate= 64.0kbits/s video:0kB audio:46kB global headers:0kB muxing overhead 0.070153%

• Compiling tutorial programs on FFMPEG

  29 janvier 2012, par iwant2learn

  How do i compile the sample programs given in FFMPEG. i am not able to compile as i get
  error as CODEC_TYPE_VIDEO undeclared. Can any one please suggest me how to compile the programs. I am using ubuntu 11.

  This is the first example :

  $ gcc -o tutorial01 tutorial01.c -lavutil -lavformat -lavcodec -lz

  This is the output I got :

  tutorial01.c: In function ‘main’: tutorial01.c:77:3: warning: ‘dump_format’ is deprecated (declared at /usr/local/include/libavformat/avformat.h:1462)
  
  tutorial01.c:82:51: error: ‘CODEC_TYPE_VIDEO’ undeclared (first use in this function)
  
  tutorial01.c:82:51: note: each undeclared identifier is reported only once for each function it appears in

  Version info :

  ffmpeg version git-N-30430-ga52f598, Copyright (c) 2000-2011 the FFmpeg developers
  
    built on May 31 2011 14:21:08 with gcc 4.5.2
  
    configuration: --enable-gpl --enable-version3 --enable-nonfree --enable-postproc --enable-libfaac --enable-libmp3lame --enable-libopencore-amrnb --enable-libopencore-amrwb --enable-libtheora --enable-libvorbis --enable-libx264 --enable-libxvid --enable-x11grab
  
    libavutil    51.  3. 0 / 51.  3. 0
  
    libavcodec   53.  6. 1 / 53.  6. 1
  
    libavformat  53.  2. 0 / 53.  2. 0
  
    libavdevice  53.  1. 0 / 53.  1. 0
  
    libavfilter   2. 11. 0 /  2. 11. 0
  
    libswscale    0. 14. 0 /  0. 14. 0
  
    libpostproc  51.  2. 0 / 51.  2. 0