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• ffmpeg : is there a fast way for extracting several thumbnails from a video without parsing the video from the beginning every time ?

  18 mars, par archie

  I tried several ways for extracting sample frames from a video file with ffmpeg. I found out that the fastest way is by placing the following command in a loop:

  ffmpeg -ss $frame_time -i "$input_video" -frames:v 1 -vf scale=256:-1 "$Work_dir/thumb$thumb_index.jpg"
  

  (I have omitted the parts of the command that are not relevant to the question, such as drawtext, hide_banner, loglevel). The variables frame_time and thumb_index are initialized before the loop and incremented by a fixed amount at every step: +1 for thumbs_index and $duration/25 for frame_time. I read in the ffmpeg documentation (https://trac.ffmpeg.org/wiki/Seeking) that having the -ss part before the -i part is very fast because the input is parsed by keyframe. For the same reason, the loop containing the command above is also much faster than commands based on "-vf fps=$thumbs_number/$duration".

  In fact, the code works pretty well. However, I can't escape a feeling of programming discomfort, because ffmpeg is called several times for each video file, and every time it has to parse the file from the beginning. I mean, if I had a function doing the same as the command above — it would parse a video from the beginning to search for a frame at a certain time — calling it n times to extract a regular sequence of n frames would be bad programming. I should change the function to parse the video file once and get all the frames I need in a single pass.

  My question is: is there a fast way for having ffmpeg parse a video file a single time, searching by keyframes and extracting a given number of frames at a given distance from one another? I am ready to take No for an answer, but one who is deeper into ffmpeg than I am might know a way. Thanks

• How to implement FFMPEG retry logic [closed]

  18 mars, par M9A

  I am recording a live stream using the following code:

  ffmpeg -i  -c copy output.mp4
  

  This works fine for occasions where the stream is segmented in the sense that it will retry if the stream drops. However if the url no longer exists or returns a code such as 403, it will still retry, resulting in an infinite loop of retrying when the stream doesnt exist.

  How can I retry for segments but maybe retry only a few times for page errors?

• Loading a larger file with ffmpeg crashes on safari mobile

  17 mars, par developer1

  My use case is to extract audio from video file to minimize the size of sent file over network. Everything works fine on a computer (chrome, safari) but it's either stuck or crashes on ios safari. AFAIK it crashes not while executing the ffmpeg command, but while trying to load the input file, which is quite big (500MB+).

  I load the ffmpeg like this:

    const baseURL = "https://unpkg.com/@ffmpeg/core-mt@0.12.6/dist/esm";
    await ffmpeg.load({
      coreURL: await toBlobURL(`${baseURL}/ffmpeg-core.js`, "text/javascript"),
      wasmURL: await toBlobURL(`${baseURL}/ffmpeg-core.wasm`, "application/wasm"),
      workerURL: await toBlobURL(
        `${baseURL}/ffmpeg-core.worker.js`,
        "text/javascript"
      ),
    });
  
  

  And I try to load the file like this:

  await ffmpeg.writeFile(inputFileName, await fetchFile(file));
  

  But it does not go past this step. How can I work around this limitation? Is there any other way to load larger files?

  Thank you.

• Convert .flac to .mp3 with ffmpeg, keeping all metadata

  17 mars, par Vito Gentile

  How can I convert .flac to .mp3 with ffmpeg, keeping all metadata (that is converting Vorbis comment in .flac files to ID3v2 metadata of .mp3)?

• FFMPEG : Invalid data found when processing input

  16 mars, par Schüler

  I am unable to upload mp3 or mp4 is there any specific path format? Here is my code. I have tried this also ffmpeg -i Video/" + Name + " -ss 01:30 -r 1 -an -vframes 1 -f mjpeg Video/" + Name + ".jpg

  exec("ffmpeg -y -i Video/" + Name + " -map_metadata -1 -ab 192k Video/" + Name + ".jpg", function(err) {
              if (err) {console.log(err)}
          console.log('Done', {'Image' : 'Video/' + Name + '.jpg'});
          });
  

  Here is the error

  { Error: Command failed: ffmpeg -y -i Video/ac9358e25dd41a69e95a72d3e71e4881 -map_metadata -1 -ab 192k Video/ac9358e25dd41a69e95a72d3e71e4881.jpg
  ffmpeg version 4.1.1 Copyright (c) 2000-2019 the FFmpeg developers
    built with gcc 8.2.1 (GCC) 20190212
    configuration: --enable-gpl --enable-version3 --enable-sdl2 --enable-fontconfig --enable-gnutls --enable-iconv --enable-libass --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
    libavutil      56. 22.100 / 56. 22.100
    libavcodec     58. 35.100 / 58. 35.100
    libavformat    58. 20.100 / 58. 20.100
    libavdevice    58.  5.100 / 58.  5.100
    libavfilter     7. 40.101 /  7. 40.101
    libswscale      5.  3.100 /  5.  3.100
    libswresample   3.  3.100 /  3.  3.100
    libpostproc    55.  3.100 / 55.  3.100
  Video/ac9358e25dd41a69e95a72d3e71e4881: Invalid data found when processing input
  
      at ChildProcess.exithandler (child_process.js:275:12)
      at emitTwo (events.js:126:13)
      at ChildProcess.emit (events.js:214:7)
      at maybeClose (internal/child_process.js:925:16)
      at Socket.stream.socket.on (internal/child_process.js:346:11)
      at emitOne (events.js:116:13)
      at Socket.emit (events.js:211:7)
      at Pipe._handle.close [as _onclose] (net.js:557:12)
    killed: false,
    code: 1,
    signal: null,
    cmd: 'ffmpeg -y -i Video/ac9358e25dd41a69e95a72d3e71e4881 -map_metadata -1 -ab 192k Video/ac9358e25dd41a69e95a72d3e71e4881.jpg' }