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• How to repair a raw H.264 stream using FFmpeg

  13 janvier 2020, par Chris Kennedy

  I apologize if I start rambling or seem incoherent.

  Preface : My house caught on fire last week.

  I have been trying to get the footage off my security camera system (Zmodo, don’t ever buy this crap) to share with the fire marshal and my insurance. I can’t get it off the "proper" way because the box doesn’t detect any drive or any file system I throw at it, and none of their viewing apps (for Android or Windows) allow video downloads.

  I was able to get the files directly from the system’s hard drive, but they’re (of course) messed up in such a way that I can’t just open up VLC (or even Zmodo’s own viewing software !) and view them. I have spent several hours scouring the web for various ways to run it through FFmpeg to see if it can repair the file, but I’ve had no luck so far and my mind is already stretched thin with everything else.

  This is the output from ffprobe :

  ffprobe version 4.2.1 Copyright (c) 2007-2019 the FFmpeg developers
  
    built with gcc 9.1.1 (GCC) 20190807
  
    configuration: --enable-gpl --enable-version3 --enable-sdl2 --enable-fontconfig --enable-gnutls --enable-iconv --enable-libass --enable-libdav1d --enable-libbluray --enable-libfreetype --enable-libmp3lame --enable-libopencore-amrnb --enable-libopencore-amrwb --enable-libopenjpeg --enable-libopus --enable-libshine --enable-libsnappy --enable-libsoxr --enable-libtheora --enable-libtwolame --enable-libvpx --enable-libwavpack --enable-libwebp --enable-libx264 --enable-libx265 --enable-libxml2 --enable-libzimg --enable-lzma --enable-zlib --enable-gmp --enable-libvidstab --enable-libvorbis --enable-libvo-amrwbenc --enable-libmysofa --enable-libspeex --enable-libxvid --enable-libaom --enable-libmfx --enable-amf --enable-ffnvcodec --enable-cuvid --enable-d3d11va --enable-nvenc --enable-nvdec --enable-dxva2 --enable-avisynth --enable-libopenmpt
  
    libavutil      56. 31.100 / 56. 31.100
  
    libavcodec     58. 54.100 / 58. 54.100
  
    libavformat    58. 29.100 / 58. 29.100
  
    libavdevice    58.  8.100 / 58.  8.100
  
    libavfilter     7. 57.100 /  7. 57.100
  
    libswscale      5.  5.100 /  5.  5.100
  
    libswresample   3.  5.100 /  3.  5.100
  
    libpostproc    55.  5.100 / 55.  5.100
  
  [h264 @ 000002479ee1c180] Format h264 detected only with low score of 1, misdetection possible!

  Then this repeats several dozen times :

      Last message repeated 1 times
  
  [h264 @ 000002479ee1de40] decode_slice_header error
  
  [h264 @ 000002479ee1de40] no frame!
  
  [h264 @ 000002479ee1de40] non-existing PPS 0 referenced

  And it finishes off with this :

  [h264 @ 000002479ee1c180] Could not find codec parameters for stream 0 (Video: h264, none): unspecified size
  
  Consider increasing the value for the 'analyzeduration' and 'probesize' options
  
  Input #0, h264, from '.\recfile_-200102-130000-135959-00001100.264':
  
    Duration: N/A, bitrate: N/A
  
      Stream #0:0: Video: h264, none, 25 fps, 25 tbr, 1200k tbn, 50 tbc

  I have tried several options with ffmpeg, including force_key_frames, setting the analyzeduration and probesize options to max_int, tried a -c copy, forcibly specified x264, tried to force a specific resolution (which it should all be standard HD video), and several others that I can’t recall at the moment.

  The video files are also accompanied by a .IDX file, but I haven’t figured out how important they are if they are at all to the video file.

  I can provide links to the smallest video and its associated IDX if needed, but if anyone can think of anything else to try on these files I’d greatly appreciate it.

• Dealing with problems in FLAC audio files with ffmpeg

  15 janvier 2020, par Seamus

  I have gotten a set of FLAC (audio) files from a friend. I copied them to my Sonos music library, and got set to enjoy a nice album. Unfortunately, Sonos would not play the files. As a result I have been getting to know ffmpeg.

  Sonos’ complaint with the FLAC files was that it was "encoded at an unsupported sample rate". With rolling eyes and shaking head, I note that the free VLC media player happily plays these files, but the product I’ve paid for (Sonos) - does not. But I digress...

  ffprobe revealed that the FLAC files contain both an Audio channel and a Video channel :

  $ ffprobe -hide_banner  -show_streams "/path/to/Myaudio.flac"
  
  
  
  
  
      Duration: 00:02:23.17, start: 0.000000, bitrate: 6176 kb/s  
  
      Stream #0:0: Audio: flac, 176400 Hz, stereo, s32 (24 bit)  
  
      Stream #0:1: Video: mjpeg (Progressive), yuvj444p(pc, bt470bg/unknown/unknown), 450x446 [SAR 72:72 DAR 225:223], 90k tbr, 90k tbn, 90k tbc (attached pic)  
  
      Metadata:  
  
        comment         : Cover (front)  

  Cool ! I guess this is how some audio players are able to display the ’album artwork’ when they play a song ? Note also that the Audio stream is reported at 176400 Hz ! Apparently I’m out of touch ; I thought that 44.1khz sampling rate effectively removed all of the ’sampling artifacts’ we could hear. Anyway, I learned that Sonos would support a max of 48kHz sampling rate, and this (the 176.4kHz rate) is what Sonos was unhappy about. I used ffmpeg to ’dumb it down’ for them :

  $ ffmpeg -i "/path/to/Myaudio.flac" -sample_fmt s32 -ar 48000 "/path/to/Myaudio48K.flac"

  This seemed to work - at least I got a FLAC file that Sonos would play. However, I also got what looks like a warning of some sort :

  [swscaler @ 0x108e0d000] deprecated pixel format used, make sure you did set range correctly
  [flac @ 0x7feefd812a00] Frame rate very high for a muxer not efficiently supporting it.
  Please consider specifying a lower framerate, a different muxer or -vsync 2

  A bit more research turned up this answer which I don’t quite understand, and then in a comment says, "not to worry" - at least wrt the swscaler part of the warning.

  And that (finally) brings me to my questions :

  1.a. What framerate, muxer & other specifications make a graphic compatible with a majority of programs that use the graphic ?

  1.b. How should I use ffmpeg to modify the Video channel to set these specifications (ref. Q 1.a.) ?

  2.a. How do I remove the Video channel from the .flac audio file ?

  2.b. How do I add a Video channel into a .flac file ?

  EDIT :

  I asked the above (4) questions after failing to accomplish a ’direct’ conversion (a single ffmpeg command) from FLAC at 176.4 kHz to ALAC (.m4a) at 48 kHz (max supported by Sonos). I reasoned that an ’incremental’ approach through a series of conversions might get me there. With the advantage of hindsight, I now see I should have posted my original failed direct conversion incantation... we live and learn.

  That said, the accepted answer below meets my final objective to convert a FLAC file encoded at 176.4kHz to an ALAC (.m4a) at 48kHz, and preserve the cover art/video channel.

• FFMPEG licencing

  14 juin 2020, par Dodu

  I am making a website that uses FFMPEG, and by extention libx264. The website takes a video and adds filters etc to it, then serves that new video to the user.

  



  There are various answers about distributing libx264 (and others) as part of a comercial product such as :

  



  https://video.stackexchange.com/questions/14802/can-i-use-ffmpeg-in-a-commercial-product/14804# : :text=Yes%2C%20you%20can%20use%20FFmpeg,LGPL)%20version%202.1%20or%20later.&text=So%2C%20yes%2C%20you%20can%20definitely,usage%2C%20distribution%2C%20and%20modification.

  



  Since I am generating content using the library, but not distributing the library itself, I'm not sure where this leaves me.

  



  Do I need a licence to libraries ? Or because there is no distribution, are licences generally not needed ?

  



  Any advice/links/other resources that may be helpful would be greatly appreciated.

  



  Thanks

  



  Dodu