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• Repair mpeg files using ffmpeg

  27 février 2014, par rsdrsd

  I have a bunch of mpeg files which are some how invalid or incorrect. I can play the files in different media players but when I upload the files and they should automagically be converted. It takes a very long time to create screenshots and it creates about 10000 screenshots instead of the 50 to be expected. The command is part of an automatic conversion app. With mp4 and other files it works great but whit mpeg it doesn't work as expected. The creation of screenshots eats up all memory and processor power.

  For creating screenshots I have tried the following :

      ffmpeg -y -i /input/file.mpeg -f image2 -aspect 16:9 -bt 20M -vsync passthrough -vf select='isnan(prev_selected_t)+gte(t-prev_selected_t\,10)' /output/file-%05d.jpg

  this just creates 2 screenshots while I expect 50 or so. The following command :

      ffmpeg -y -i /input/file.mpeg -f image2 -vf fps=fps=1/10 -aspect 16:9 -vsync passthrough -bt 20M /output/file-%05d.jpg

  gave me errors about buffers :

      ffmpeg version N-39361-g1524b0f Copyright (c) 2000-2014 the FFmpeg developers
  
        built on Feb 26 2014 23:46:40 with gcc 4.4.7 (GCC) 20120313 (Red Hat 4.4.7-4)
  
        configuration: --prefix=/home/example/ffmpeg_build --extra-cflags=-I/home/example/ffmpeg_build/include --extra-ldflags=-L/home/example/ffmpeg_build/lib --bindir=/home/example/bin --extra-libs=-ldl --enable-gpl --enable-nonfree --enable-libfdk_aac --enable-libmp3lame --enable-libopus --enable-libvorbis --enable-libvpx --enable-libx264 --enable-libfreetype --enable-libspeex --enable-libtheora
  
        libavutil      52. 66.100 / 52. 66.100
  
        libavcodec     55. 52.102 / 55. 52.102
  
        libavformat    55. 33.100 / 55. 33.100
  
        libavdevice    55. 10.100 / 55. 10.100
  
        libavfilter     4.  2.100 /  4.  2.100
  
        libswscale      2.  5.101 /  2.  5.101
  
        libswresample   0. 18.100 /  0. 18.100
  
        libpostproc    52.  3.100 / 52.  3.100
  
      [mp3 @ 0x200d7c0] Header missing
  
      [mpegts @ 0x2008a60] DTS discontinuity in stream 0: packet 6 with DTS 34185, packet 7 with DTS 8589926735
  
      [mpegts @ 0x2008a60] Invalid timestamps stream=0, pts=7157, dts=8589932741, size=150851
  
      Input #0, mpegts, from '/home/example/app/uploads/21.mpeg':
  
        Duration: 00:03:14.75, start: 0.213000, bitrate: 26112 kb/s
  
        Program 1
  
  Stream #0:0[0x3e9]: Video: mpeg2video (Main) ([2][0][0][0] / 0x0002), yuv420p(tv), 1440x1080 [SAR 4:3 DAR 16:9], max. 25000 kb/s, 29.97 fps, 60 tbr, 90k tbn, 59.94 tbc
  
  Stream #0:1[0x3ea]: Audio: mp2 ([3][0][0][0] / 0x0003), 48000 Hz, stereo, s16p, 384 kb/s
  
      [swscaler @ 0x1ff9860] deprecated pixel format used, make sure you did set range correctly
  
      Output #0, image2, to '/home/example/app/uploads/21-%05d.jpg':
  
        Metadata:
  
  encoder         : Lavf55.33.100
  
  Stream #0:0: Video: mjpeg, yuvj420p, 1440x1080 [SAR 4:3 DAR 16:9], q=2-31, 200 kb/s, 90k tbn, 0.10 tbc
  
      Stream mapping:
  
        Stream #0:0 -> #0:0 (mpeg2video -> mjpeg)
  
      Press [q] to stop, [?] for help
  
      [mpegts @ 0x2008a60] Invalid timestamps stream=0, pts=7157, dts=8589932741, size=150851
  
      [output stream 0:0 @ 0x1ff2ba0] 100 buffers queued in output stream 0:0, something may be wrong.
  
      [output stream 0:0 @ 0x1ff2ba0] 1000 buffers queued in output stream 0:0, something may be wrong.

  and it creates about 10000 screenshots while I expect 50.

  Now I have read some where on how to repair some broken files. For this I have the following command :

      ffmpeg -y -i input.mpeg -codec:v copy -codec:a copy output.mpeg

  This however creates a file somewhat smaller, but if I run the same command on the output again, I would expect that it creates the same file, but the following command

      ffmpeg -y -i output.mpeg -codec:v copy -codec:a copy output2.mpeg

  returns a file which is much smaller and runs for only a few seconds while the original was about 3 minutes.

  If I run the "repair" commands for a not broken mpeg it results the first time I run the command in a much smaller file. With ffprobe I checked what changed but the only thing that changes is MPEG-TS to MPEG-PS.

  If I run the command over an mp4 file it results in exactly the same file as expected. Does someone have a clue of what is going wrong. It is boggling me now for about two days and I really have no clue. Or does someone have a good suggestion on how to extract screenshots every 10 seconds without creating too much screenshots and eating up all memory and processor power.

• To create an android app where I am able to add color filters to a recorded video

  27 novembre 2014, par Ramesh Kannan

  I’m trying to create an app where I am able to add color filters to a recorded video.

  I’ve done research and I can’t piece it all together. I’ve looked into using OpenCV to record a video. The problem is, when I use the sample APK in OpenCV it trigger out the camera and color effects are applied simultaneously then stored as a picture but what I need is after recording the video to apply color effects in the preview mode. I don’t know how to implement OpenCV in my android application.

  I’ve also heard about "ffmpeg" which is an open-source platform for recording, converting, playing and streaming video and audio but I didn’t get any idea to implement it to my project.

  Lastly, I’ve looked into OpenCV. Tried using OpenCV, but I haven’t had much either.

  Do you have steps / procedures / code / example on integrating video filters (FFMPEG) on Android for the following needs.

  • I used to record the video,
  • then dividing it as frames and apply filters.

• lavu/tx : invert permutation lookups

  27 février 2021, par Lynne

  lavu/tx : invert permutation lookups
  out[lut[i]] = in[i] lookups were 4.04 times(!) slower than
  
  out[i] = in[lut[i]] lookups for an out-of-place FFT of length 4096.
  The permutes remain unchanged for anything but out-of-place monolithic
  
  FFT, as those benefit quite a lot from the current order (it means
  
  there's only 1 lookup necessary to add to an offset, rather than
  
  a full gather).
  The code was based around non-power-of-two FFTs, so this wasn't
  
  benchmarked early on.
  

  • [DH] libavutil/tx.c
  • [DH] libavutil/tx_priv.h
  • [DH] libavutil/tx_template.c