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• Is there a set of working P/Invoke declarations for FFMpeg, libavutil, libavformat and libavcodec in .NET ?

  30 août 2011, par casperOne

  I'm currently looking to access libavutil, libavformat and libavcodec (all part of FFMpeg) from .NET.

  Currently, I'm getting the libraries from the automated builds of the shared FFMpeg package performed every night for Windows 32-bit.

  I am also using the code from the ffmpeg-sharp project. In that project, I have removed a number of classes that were not compiling (they are wrapper classes not the P/Invoke declarations).

  The code compiles fine, but I am running into a few issues.

  First, it appears that the build of av*.dll uses the cdecl calling convention, as I was receiving a number of PInvokeStackImbalanceException when trying to call av_open_input_file. This was easy enough to change to get it to work right. The AVFormatContext structure is populated.

  After that, I want to call av_find_stream_info to get information about the streams in the file. However, when calling that with the AVFormatContext retrieved from the call to av_open_input_file, an AccessViolationException is thrown indicating that I am trying to read or write from protected memory.

  Has anyone used P/Invoke to access the libavutil, libavformat and libavcodec dll libraries through P/Invoke and have gotten it to work ?

  I should mention that working with the command-line version of FFMpeg, while a solution, is not a viable solution in this case, access needs to occur through the libraries. The reason for this is that I'd have to thrash the disk way too much to do what I need to do (I have to do a frame-by-frame analysis of some very high definition video) and I want to avoid the disk as much as possible.

• Programming Language Levels

  20 mai 2011, par Multimedia Mike — Programming

  I’ve been doing this programming thing for some 20 years now. Things sure do change. One change I ponder from time to time is the matter of programming language levels. Allow me to explain.

  The 1990s
  When I first took computer classes in the early 1990s, my texts would classify computer languages into 3 categories, or levels. The lower the level, the closer to the hardware ; the higher the level, the more abstract (and presumably, easier to use). I recall that the levels went something like this :

  • High level : Pascal, BASIC, Logo, Fortran
  • Medium level : C, Forth
  • Low level : Assembly language

  Keep in mind that these were the same texts which took the time to explain the history of computers from mainframes -> minicomputers -> a relatively recent phenomenon called microcomputers or "PCs".

  Somewhere in the mid-late 1990s, when I was at university, I was introduced to a new tier :

  • Very high level : Perl, shell scripting

  I think there was some debate among my peers about whether C++ and Java were properly classified as high or very high level. The distinction between high and very high, in my observation, seemed to be that very high level languages had more complex data structures (at the very least, a hash / dictionary / associative array / key-value map) built into the language, as well as implicit memory management.

  Modern Day
  These days, the old hierarchy is apparently forgotten (much like minicomputers). I observe that there is generally a much simpler 2-tier classification :

  • Low level : C, assembly language
  • High level : absolutely every other programming language in wide use today

  I find myself wondering where C++ and Objective-C fit in this classification scheme. Then I remember that it doesn’t matter and this is all academic.

  Relevancy
  I think about this because I have pretty much stuck to low-level programming all of my life, mostly due to my interest in game and multimedia-type programming. But the trends in computing have favored many higher level languages and programming paradigms. I woke up one day and realized that the kind of work I often do — lower level stuff — is not very common.

  I’m not here to argue that low or high level is superior. You know I’m all about using the appropriate tool for the job. But I sometimes find myself caught between worlds, having the defend and explain one to the other.

  • On one hand, it’s not unusual for the multitudes of programmers working at the high level to gasp and wonder why I or anyone else would ever use C or assembly language for anything when there are so many beautiful high level languages. I patiently explain that those languages have to be written in some other language (at first) and that they need to run on some operating system and that most assuredly won’t be written in a high level language. For further reading, I refer them to Joel Spolsky’s great essay called Back to Basics which describes why it can be useful to know at least a little bit about how the computer does what it does at the lowest levels.
  • On the other hand, believe it or not, I sometimes have to defend the merits of high level languages to my low level brethren. I’ll often hear variations of, "Any program can be written in C. Using a high level language to achieve the same will create a slow and bloated solution." I try to explain that the trade-off in time to complete the programming task weighed against the often-negligible performance hit of what is often an I/O-bound operation in the first place makes it worthwhile to use the high level language for a wide variety of tasks.

    Or I just ignore them. That’s actually the best strategy.

• Extract Video Frames In Python

  22 avril 2017, par TheNone

  I want to extract video frames and save them as image.

  import os, sys
  
  from PIL import Image
  
  
  
  a, b, c = os.popen3("ffmpeg -i test.avi")
  
  out = c.read()
  
  dp = out.index("Duration: ")
  
  duration = out[dp+10:dp+out[dp:].index(",")]
  
  hh, mm, ss = map(float, duration.split(":"))
  
  total = (hh*60 + mm)*60 + ss
  
  for i in xrange(9):
  
      t = (i + 1) * total / 10
  
      os.system("ffmpeg -i test.avi -ss %0.3fs frame%i.png" % (t, i))

  But I have this error :

  FFmpeg version CVS, Copyright (c) 2000-2004 Fabrice Bellard
  
  Mac OSX universal build for ffmpegX
  
    configuration:  --enable-memalign-hack --enable-mp3lame --enable-gpl --disable-vhook --disable-ffplay --disable-ffserver --enable-a52 --enable-xvid --enable-faac --enable-faad --enable-amr_nb --enable-amr_wb --enable-pthreads --enable-x264 
  
    libavutil version: 49.0.0
  
    libavcodec version: 51.9.0
  
    libavformat version: 50.4.0
  
    built on Apr 15 2006 04:58:19, gcc: 4.0.1 (Apple Computer, Inc. build 5250)
  
  Input #0, avi, from 'test.avi':
  
    Duration: 00:00:30.5, start: 0.000000, bitrate: 465 kb/s
  
    Stream #0.0, 25.00 fps(r): Video: mpeg4, yuv420p, 640x480
  
    Stream #0.1: Audio: mp3, 32000 Hz, mono, 32 kb/s
  
  Unable for find a suitable output format for 'frame0.png'

  Edit : ffmpeg -formats

  FFmpeg version CVS, Copyright (c) 2000-2004 Fabrice Bellard
  
  Mac OSX universal build for ffmpegX
  
    configuration:  --enable-memalign-hack --enable-mp3lame --enable-gpl --disable-vhook --disable-ffplay --disable-ffserver --enable-a52 --enable-xvid --enable-faac --enable-faad --enable-amr_nb --enable-amr_wb --enable-pthreads --enable-x264 
  
    libavutil version: 49.0.0
  
    libavcodec version: 51.9.0
  
    libavformat version: 50.4.0
  
    built on Apr 15 2006 04:58:19, gcc: 4.0.1 (Apple Computer, Inc. build 5250)
  
  File formats:
  
    E 3g2             3gp2 format
  
    E 3gp             3gp format
  
   D  4xm             4X Technologies format
  
   D  RoQ             Id RoQ format
  
   D  aac             ADTS AAC
  
   DE ac3             raw ac3
  
    E adts            ADTS AAC
  
   DE aiff            Audio IFF
  
   DE alaw            pcm A law format
  
   DE amr             3gpp amr file format
  
   DE asf             asf format
  
    E asf_stream      asf format
  
   DE au              SUN AU Format
  
   DE avi             avi format
  
   D  avs             avs format
  
    E crc             crc testing format
  
   D  daud            D-Cinema audio format
  
   D  dts             raw dts
  
   DE dv              DV video format
  
    E dvd             MPEG2 PS format (DVD VOB)
  
   D  ea              Electronic Arts Multimedia Format
  
   DE ffm             ffm format
  
   D  film_cpk        Sega FILM/CPK format
  
   D  flic            FLI/FLC/FLX animation format
  
   DE flv             flv format
  
    E framecrc        framecrc testing format
  
   DE gif             GIF Animation
  
   DE h261            raw h261
  
   DE h263            raw h263
  
   DE h264            raw H264 video format
  
   D  idcin           Id CIN format
  
   DE image           image sequence
  
   DE image2          image2 sequence
  
   DE image2pipe      piped image2 sequence
  
   DE imagepipe       piped image sequence
  
   D  ingenient       Ingenient MJPEG
  
   D  ipmovie         Interplay MVE format
  
   DE m4v             raw MPEG4 video format
  
   D  matroska        Matroska file format
  
   DE mjpeg           MJPEG video
  
   D  mm              American Laser Games MM format
  
   DE mmf             mmf format
  
    E mov             mov format
  
   D  mov,mp4,m4a,3gp,3g2,mj2 QuickTime/MPEG4/Motion JPEG 2000 format
  
    E mp2             MPEG audio layer 2
  
   DE mp3             MPEG audio layer 3
  
    E mp4             mp4 format
  
   DE mpeg            MPEG1 System format
  
    E mpeg1video      MPEG video
  
    E mpeg2video      MPEG2 video
  
   DE mpegts          MPEG2 transport stream format
  
   D  mpegvideo       MPEG video
  
    E mpjpeg          Mime multipart JPEG format
  
   DE mulaw           pcm mu law format
  
   D  nsv             NullSoft Video format
  
    E null            null video format
  
   DE nut             nut format
  
   D  nuv             NuppelVideo format
  
   D  ogg             Ogg
  
    E psp             psp mp4 format
  
   D  psxstr          Sony Playstation STR format
  
   DE rawvideo        raw video format
  
   D  redir           Redirector format
  
   DE rm              rm format
  
    E rtp             RTP output format
  
   D  rtsp            RTSP input format
  
   DE s16be           pcm signed 16 bit big endian format
  
   DE s16le           pcm signed 16 bit little endian format
  
   DE s8              pcm signed 8 bit format
  
   D  sdp             SDP
  
   D  shn             raw shorten
  
   D  smk             Smacker Video
  
   D  sol             Sierra SOL Format
  
    E svcd            MPEG2 PS format (VOB)
  
   DE swf             Flash format
  
   D  tta             true-audio
  
   DE u16be           pcm unsigned 16 bit big endian format
  
   DE u16le           pcm unsigned 16 bit little endian format
  
   DE u8              pcm unsigned 8 bit format
  
    E vcd             MPEG1 System format (VCD)
  
   D  vmd             Sierra VMD format
  
    E vob             MPEG2 PS format (VOB)
  
   DE voc             Creative Voice File format
  
   DE wav             wav format
  
   D  wc3movie        Wing Commander III movie format
  
   D  wsaud           Westwood Studios audio format
  
   D  wsvqa           Westwood Studios VQA format
  
   DE yuv4mpegpipe    YUV4MPEG pipe format
  
  
  
  Image formats (filename extensions, if any, follow):
  
   DE gif    gif
  
  
  
  Codecs:
  
   D V    4xm
  
   D V D  8bps
  
   DEA    aac
  
   D V D  aasc
  
   DEA    ac3
  
   DEA    adpcm_4xm
  
   DEA    adpcm_adx
  
   DEA    adpcm_ct
  
   DEA    adpcm_ea
  
   DEA    adpcm_ima_dk3
  
   DEA    adpcm_ima_dk4
  
   DEA    adpcm_ima_qt
  
   DEA    adpcm_ima_smjpeg
  
   DEA    adpcm_ima_wav
  
   DEA    adpcm_ima_ws
  
   DEA    adpcm_ms
  
   DEA    adpcm_sbpro_2
  
   DEA    adpcm_sbpro_3
  
   DEA    adpcm_sbpro_4
  
   DEA    adpcm_swf
  
   DEA    adpcm_xa
  
   DEA    adpcm_yamaha
  
   D A    alac
  
   DEA    amr_nb
  
   DEA    amr_wb
  
   DEV D  asv1
  
   DEV D  asv2
  
   D V D  avs
  
   D V    bmp
  
   D V D  camstudio
  
   D V D  camtasia
  
   D V D  cinepak
  
   D V D  cljr
  
   D A    cook
  
   D V D  cyuv
  
   DES    dvbsub
  
   DES    dvdsub
  
   DEV D  dvvideo
  
   DEV D  ffv1
  
   DEVSD  ffvhuff
  
   D A    flac
  
   D V D  flic
  
   DEVSD  flv
  
   D V D  fraps
  
   DEA    g726
  
   DEV D  h261
  
   DEVSDT h263
  
   D VSD  h263i
  
    EV    h263p
  
   DEV DT h264
  
   DEVSD  huffyuv
  
   D V D  idcinvideo
  
   D V D  indeo2
  
   D V    indeo3
  
   D A    interplay_dpcm
  
   D V D  interplayvideo
  
    EV    jpegls
  
   D V    kmvc
  
    EV    ljpeg
  
   D V D  loco
  
   D A    mace3
  
   D A    mace6
  
   D V D  mdec
  
   DEV D  mjpeg
  
   D V D  mjpegb
  
   D V D  mmvideo
  
   DEA    mp2
  
   DEA    mp3
  
   D A    mp3adu
  
   D A    mp3on4
  
   DEVSDT mpeg1video
  
   DEVSDT mpeg2video
  
   DEVSDT mpeg4
  
   D A    mpeg4aac
  
   D VSDT mpegvideo
  
   DEVSD  msmpeg4
  
   DEVSD  msmpeg4v1
  
   DEVSD  msmpeg4v2
  
   D V D  msrle
  
   D V D  msvideo1
  
   D V D  mszh
  
   D V D  nuv
  
   DEV    pam
  
   DEV    pbm
  
   DEA    pcm_alaw
  
   DEA    pcm_mulaw
  
   DEA    pcm_s16be
  
   DEA    pcm_s16le
  
   DEA    pcm_s24be
  
   DEA    pcm_s24daud
  
   DEA    pcm_s24le
  
   DEA    pcm_s32be
  
   DEA    pcm_s32le
  
   DEA    pcm_s8
  
   DEA    pcm_u16be
  
   DEA    pcm_u16le
  
   DEA    pcm_u24be
  
   DEA    pcm_u24le
  
   DEA    pcm_u32be
  
   DEA    pcm_u32le
  
   DEA    pcm_u8
  
   DEV    pgm
  
   DEV    pgmyuv
  
   DEV    png
  
   DEV    ppm
  
   D A    qdm2
  
   D V D  qdraw
  
   D V D  qpeg
  
   D V D  qtrle
  
   DEV    rawvideo
  
   D A    real_144
  
   D A    real_288
  
   D A    roq_dpcm
  
   D V D  roqvideo
  
   D V D  rpza
  
   DEV D  rv10
  
   DEV D  rv20
  
   D A    shorten
  
   D A    smackaud
  
   D V    smackvid
  
   D V D  smc
  
   DEV    snow
  
   D A    sol_dpcm
  
   DEA    sonic
  
    EA    sonicls
  
   D V D  sp5x
  
   DEV D  svq1
  
   D VSD  svq3
  
   D V    theora
  
   D V D  truemotion1
  
   D V D  truemotion2
  
   D A    truespeech
  
   D A    tta
  
   D V D  ultimotion
  
   D V    vc9
  
   D V D  vcr1
  
   D A    vmdaudio
  
   D V D  vmdvideo
  
   D A    vorbis
  
   D V    vp3
  
   D V D  vqavideo
  
   D A    wmav1
  
   D A    wmav2
  
   DEVSD  wmv1
  
   DEVSD  wmv2
  
   D V D  wnv1
  
   D A    ws_snd1
  
   D A    xan_dpcm
  
   D V D  xan_wc3
  
   D V D  xl
  
    EV    xvid
  
   DEV D  zlib
  
   D V    zmbv
  
  
  
  Supported file protocols:
  
   file: pipe: udp: rtp: tcp: http:
  
  Frame size, frame rate abbreviations:
  
   ntsc pal qntsc qpal sntsc spal film ntsc-film sqcif qcif cif 4cif
  
  Motion estimation methods:
  
   zero(fastest) full(slowest) log phods epzs(default) x1 hex umh iter
  
  
  
  Note, the names of encoders and decoders dont always match, so there are
  
  several cases where the above table shows encoder only or decoder only entries
  
  even though both encoding and decoding are supported for example, the h263
  
  decoder corresponds to the h263 and h263p encoders, for file formats its even
  
  worse

  What is wrong in my code ? Thanks in advance