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• Damaged h264 stream not working with ffmpeg but working with vlc or mplayer

  15 avril 2013, par gregoiregentil

  I have a h264 file, coming from an rtsp stream, that is slightly damaged. Some frames are altered.

  ffmpeg reports :

  ffmpeg -i stream.mpg 
  
  ffmpeg version 0.8.6-4:0.8.6-0ubuntu0.12.04.1, Copyright (c) 2000-2013 the Libav developers
  
    built on Apr  2 2013 17:00:59 with gcc 4.6.3
  
  *** THIS PROGRAM IS DEPRECATED ***
  
  This program is only provided for compatibility and will be removed in a future release. Please use avconv instead.
  
  
  
  Seems stream 0 codec frame rate differs from container frame rate: 180000.00 (180000/1) -> 90000.00 (180000/2)
  
  Input #0, mpegts, from 'a.mpg':
  
    Duration: 00:03:18.84, start: 93370.745522, bitrate: 2121 kb/s
  
    Program 1 
  
      Stream #0.0[0x44](): Video: h264 (Baseline), yuv420p, 640x480, 90k tbr, 90k tbn, 180k tbc
  
  At least one output file must be specified

  I can play the file with VLC or mplayer. Obviously, the damaged frames are "kind of blurred" but it's working. mplayer reports :

  mplayer stream.mpg
  
  MPlayer2 UNKNOWN (C) 2000-2011 MPlayer Team
  
  mplayer: could not connect to socket
  
  mplayer: No such file or directory
  
  Failed to open LIRC support. You will not be able to use your remote control.
  
  
  
  Playing stream.mpg.
  
  Detected file format: MPEG-2 transport stream format (libavformat)
  
  [lavf] stream 0: video (h264), -vid 0
  
  LAVF: Program 1 
  
  VIDEO:  [H264]  640x480  0bpp  90000.000 fps    0.0 kbps ( 0.0 kbyte/s)
  
  Load subtitles in .
  
  [ass] auto-open
  
  ==========================================================================
  
  Opening video decoder: [ffmpeg] FFmpeg's libavcodec codec family
  
  Asking decoder to use 2 threads if supported.
  
  Selected video codec: [ffh264] vfm: ffmpeg (FFmpeg H.264)
  
  ==========================================================================
  
  Audio: no sound
  
  Starting playback...
  
  V:   0.0   0/  0 ??% ??% ??,?% 0 0 
  
  Movie-Aspect is undefined - no prescaling applied.
  
  VO: [xv] 640x480 => 640x480 Planar YV12 
  
  V:93370.7   0/  0 ??% ??% ??,?% 0 0 
  
  No pts value from demuxer to use for frame!
  
  Video pts after filters MISSING
  
  V:93370.7   0/  0 ??% ??% ??,?% 0 0 
  
  No pts value from demuxer to use for frame!
  
  Video pts after filters MISSING
  
  V:93370.7   0/  0 ??% ??% ??,?% 0 0 
  
  No pts value from demuxer to use for frame!
  
  Video pts after filters MISSING
  
  V:93370.7   0/  0 ??% ??% ??,?% 0 0 
  
  No pts value from demuxer to use for frame!
  
  Video pts after filters MISSING
  
  V:93370.7   0/  0 ??% ??% ??,?% 0 0 
  
  No pts value from demuxer to use for frame!
  
  Video pts after filters MISSING
  
  V:93370.7   0/  0 ??% ??% ??,?% 0 0 
  
  No pts value from demuxer to use for frame!
  
  Video pts after filters MISSING
  
  V:93370.7   0/  0 ??% ??% ??,?% 0 0 
  
  No pts value from demuxer to use for frame!

  When I try to re-encode the file with :

  ffmpeg -i stream.mpg -fflags +genpts -an -vcodec mpeg4 -r 65535/2733 stream.mp4

  ffmpeg seems to jump over the altered frames. The length of stream.mp4 << length of stream.mpg

  How could I fix this problem, i.e. having ffmpeg to output something similar to what mplayer and vlc output ?

• Started Programming Young

  6 septembre 2011, par Multimedia Mike — Programming

  I have some of the strangest memories of my struggles to jump into computer programming.

  Back To BASIC
  I remember doing some Logo programming on Apple II computers at school in 5th grade (1987 timeframe). But that was mostly driving turtle graphics. Then I remember doing some TRS-80 BASIC in 7th grade, circa 1989. Emboldened by what very little I had learned in perhaps the week or 2 we took in a science class to do this, I tried a little GW-BASIC on my family’s “IBM-PC compatible” computer (they were still called that back then). I still remember what my first program consisted of. Even back then I was interested in manipulating graphics and color on a computer screen. Thus :

  10 color 1
  20 print "This is color 1"
  30 color 2
  40 print "This is color 2"
  ...
  

  And so on through 15 colors. Hey, it did the job– it demonstrated the 15 different colors you could set in text mode.

  What’s FOR For ?
  That 7th grade computer unit in science class wasn’t very thick on computer science details. I recall working with a lab partner to transcribe code listings into a computer (and also saving my work to a storage cassette). We also developed form processing programs that would print instructions to input text followed by an “INPUT I$” statement to obtain the user’s output.

  I remember there was some situation where we needed a brief delay between input and printing. The teacher told us to use a construct of the form :

  10 FOR I = 1 TO 20000
  20 NEXT I
  

  We had to calibrate the number based on our empirical assessment of how long it lasted but I recall that the number couldn’t be much higher than about 32000, for reasons that would become clearer much later.

  Imagine my confusion when I would read and try to comprehend BASIC program code I would find in magazines. I would of course see that FOR..NEXT construct all over the place but obviously not in the context of introducing deliberate execution delays. Indeed, my understanding of one of the fundamental building blocks of computer programming — iteration — was completely skewed because of this early lesson.

  Refactoring
  Somewhere along the line, I figured out that the FOR..NEXT could be used to do the same thing a bunch of times, possibly with different values. A few years after I had written that color program, I found it again and realized that I could write it as :

  10 for I = 1 to 15
  20 color I
  30 print I
  40 next I
  

  It still took me a few more years to sort out the meaning of WHILE..WEND, though.

• avcodec/mpegvideo_dec : Don't use MotionEstContext as scratch space

  30 octobre 2022, par Andreas Rheinhardt

  avcodec/mpegvideo_dec : Don't use MotionEstContext as scratch space
  Decoders that might use quarter pixel motion estimation
  
  (namely MPEG-4 as well as the VC-1 family) currently
  
  use MpegEncContext.me.qpel_(put|avg) as scratch space
  
  for pointers to arrays of function pointers.
  
  (MotionEstContext contains such pointers as it supports
  
  quarter pixel motion estimation.) The MotionEstContext
  
  is unused apart from this for the decoding part of
  
  mpegvideo.
  Using the context at all is for decoding is actually
  
  unnecessary and easily avoided : All codecs with
  
  quarter pixels set me.qpel_avg to qdsp.avg_qpel_pixels_tab,
  
  so one can just unconditionally use this in ff_mpv_reconstruct_mb().
  
  MPEG-4 sets qpel_put to qdsp.put_qpel_pixels_tab
  
  or to qdsp.put_no_rnd_qpel_pixels_tab based upon
  
  whether the current frame is a b-frame with no_rounding
  
  or not, while the VC-1-based decoders set it to
  
  qdsp.put_qpel_pixels_tab unconditionally. Given
  
  that no_rounding is always zero for VC-1, using
  
  the same check for VC-1 as well as for MPEG-4 would work.
  
  Since ff_mpv_reconstruct_mb() already has exactly
  
  the right check (for hpeldsp), it can simply be reused.
  (This change will result in ff_mpv_motion() receiving
  
  a pointer to an array of NULL function pointers instead
  
  of a NULL pointer for codecs without qpeldsp (like MPEG-1/2).
  
  It doesn't matter.)
  Signed-off-by : Andreas Rheinhardt <andreas.rheinhardt@outlook.com>
  

  • [DH] libavcodec/h263dec.c
  • [DH] libavcodec/mpv_reconstruct_mb_template.c
  • [DH] libavcodec/mss2.c
  • [DH] libavcodec/vc1dec.c