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• libavformat : add RCWT closed caption muxex

  14 janvier 2024, par Marth64

  libavformat : add RCWT closed caption muxex
  Signed-off-by : Marth64 <marth64@proxyid.net>
  Raw Captions With Time (RCWT) is a format native to ccextractor, a commonly
  
  used open source tool for processing 608/708 closed caption (CC) sources.
  
  It can be used to archive the original, raw CC bitstream and to produce
  
  a source file file for later CC processing or conversion. As a result,
  
  it also allows for interopability with ccextractor for processing CC data
  
  extracted via ffmpeg. The format is simple to parse and can be used
  
  to retain all lines and variants of CC.
  A free specification of RCWT can be found here :
  
  https://github.com/CCExtractor/ccextractor/blob/master/docs/BINARY_FILE_FORMAT.TXT
  
  This muxer implements the specification as of 01/05/2024, which has
  
  been stable and unchanged for 10 years as of this writing.
  This muxer will have some nuances from the way that ccextractor muxes RCWT.
  
  No compatibility issues when processing the output with ccextractor
  
  have been observed as a result of this so far, but mileage may vary
  
  and outputs will not be a bit-exact match.
  Specifically, the differences are :
  
  (1)  This muxer will identify as "FF" as the writing program identifier, so
  
  as to be honest about the output's origin.
  (2)  ffmpeg's MPEG-1/2, H264, HEVC, etc. decoders extract closed captioning
  
  data differently than ccextractor from embedded SEI/user data.
  
  For example, DVD captioning bytes will be translated to ATSC A53 format.
  
  This allows ffmpeg to handle 608/708 in a consistant way downstream.
  
  This is a lossless conversion and the meaningful data is retained.
  (3)  This muxer will not alter the extracted data except to remove invalid
  
  packets in between valid CC blocks. On the other hand, ccextractor
  
  will by default remove mid-stream padding, and add padding at the end
  
  of the stream (in order to convey the end time of the source video).
  

  • [DH] Changelog
  • [DH] doc/muxers.texi
  • [DH] libavformat/Makefile
  • [DH] libavformat/allformats.c
  • [DH] libavformat/rcwtenc.c
  • [DH] tests/fate/subtitles.mak

• ffmpeg chains parameters and options while being used in a loop

  10 janvier 2024, par Simon Nazarenko

  I got a code that generates videos from scratch (got gifs, captions and audio). It works amazing when done once, however, when put in a loop and it should create more than 1 video it freezes being caused by memory leak. Upon investigation I realized that ffmpeg (v1.1.0) chains the loop iterations carrying the parameters and options from the first iteration to the second. It then breaks (overwrites) the first video and infinitely writes the second.

  


  This is my dependency

  


  const ffmpeg = require("fluent-ffmpeg")()
  .setFfprobePath(ffprobe.path)
  .setFfmpegPath(ffmpegInstaller.path)


  


  It looks like this

  


  async function convertGifToVideo(
  gifFile,
  audioFile,
  subtitlesFile,
  tempDirectory
) {
  return new Promise((resolve, reject) => {
    const outputFile = `${tempDirectory}/video_${Date.now()}.mp4`
    
    ffmpeg
      .input(gifFile)
      .inputFormat("gif")
      .inputOptions("-stream_loop -1")
      .input(audioFile)
      .outputOptions("-shortest")
      .outputOptions(`-vf subtitles=${subtitlesFile}`)
      .outputOptions("-report")
      .output(outputFile)
      .on("end", () => {
        console.log(`Combined ${gifFile} and ${audioFile} into ${outputFile}`)
        resolve(outputFile)
      })
      .on("error", (err, stdout, stderr) => {
        console.error("Error combining GIF and audio:", err)
        console.error("ffmpeg stdout:", stdout)
        console.error("ffmpeg stderr:", stderr)
        reject(err)
      })
      .run()
  })
}


  


  And it's called in a loop

  


  for (const key in script) {
    if (script.hasOwnProperty(key)) {
      ...stuff

      const videoFileName = await convertGifToVideo(
        gifFileName,
        audioFileName,
        subtitlesFileName,
        tempDirectory
      )
    }
  }


  


  Here is a piece of log from the first video generation

  


  


  ffmpeg started on 2024-01-10 at 02:58:52
Report written to "ffmpeg-20240110-025852.log"
Command line :
/home/simon/Documents/AFYTUBE/node_modules/@ffmpeg-installer/linux-x64/ffmpeg -f gif -stream_loop -1 -i ./temp/gif_funny_frogs.gif -i ./temp/funny_frogs.mp3 -y -shortest -vf "subtitles=./temp/funny_frogs.srt" -report ./temp/video_1704880732780.mp4

  


  


  Here is a piece of log from the second one

  


  


  /home/simon/Documents/AFYTUBE/node_modules/@ffmpeg-installer/linux-x64/ffmpeg -f gif -stream_loop -1 -i ./temp/gif_funny_frogs.gif -i ./temp/funny_frogs.mp3 -f gif -stream_loop -1 -i ./temp/gif_leg_exercises.gif -i ./temp/leg_exercises.mp3 -y -shortest -vf "subtitles=./temp/funny_frogs.srt" -report -shortest -vf "subtitles=./temp/leg_exercises.srt" -report ./temp/video_1704880732780.mp4 ./temp/video_1704880750879.mp4

  


  


  Any ideas what I am doing wrong ?

  


• FFMPEG - copy the SPECIFED tracks only, ignore all others

  10 janvier 2024, par GDP

  I have some very strange MP4 files that we get regularly for processing created by Wowza. Neither FFMPEG or MEDIAINFO can detect that there are subtitles soft-coded in them, but they ARE there, I can extract them with ccextractor, and when they're played, the captions appear later in the video where the actually start in the timeline.

  


  I've tried every variation of copying with/without re-encoding, but all the answers show how to "omit" the subtitles with -sn such as these :

  


   ffmpeg -i 3078.mp4 -c copy -sn 3078_sn.mp4
 ffmpeg -i 3078.mp4 -c:v libx264 -c:a ac3 -map 0:v:0 -map 0:a:1 3078_sn.mp4
 ffmpeg -i 3078.mp4 -map 0:v:0 -map 0:a:0  -map -0:s -map -0:d  -c copy 3078_sn2.mp4 -y


  


  FFprobe :

  


  ffprobe 3078.mp4 -hide_banner
[mov,mp4,m4a,3gp,3g2,mj2 @ 000001ef2bcd9e00] multiple fourcc not supported
Input #0, mov,mp4,m4a,3gp,3g2,mj2, from '3078.mp4':
  Metadata:
    major_brand     : f4v
    minor_version   : 0
    compatible_brands: isommp42m4v
    creation_time   : 2024-01-09T19:59:28.000000Z
  Duration: 02:17:18.47, start: 0.000000, bitrate: 2165 kb/s
  Stream #0:0[0x1](eng): Video: h264 (Main) (avc1 / 0x31637661), yuv420p(progressive), 1280x720 [SAR 1:1 DAR 16:9], 1902 kb/s, 29.96 fps, 29.97 tbr, 90k tbn (default)
    Metadata:
     creation_time   : 2024-01-09T19:59:28.000000Z
     handler_name    : WowzaStreamingEngine
     vendor_id       : [0][0][0][0]
     encoder         : WowzaStreamingEngine
  Stream #0:1[0x2](eng): Audio: aac (LC) (mp4a / 0x6134706D), 48000 Hz, stereo, fltp, 257 kb/s (default)
    Metadata:
     creation_time   : 2024-01-09T19:59:28.000000Z
     handler_name    : WowzaStreamingEngine
     vendor_id       : [0][0][0][0]
  Stream #0:2[0x3](eng): Data: none (amf0 / 0x30666D61), 1 kb/s (default)
    Metadata:
     creation_time   : 2024-01-09T19:59:28.000000Z
     handler_name    : WowzaStreamingEngine
Unsupported codec with id 0 for input stream 2


  


  The problem seems to be that FFMPEG isn't detecting they're there, and so copies them anyways. My assumption is that they're not stored in the header of the MP4 properly (or however that's done), so get because they're later detect, but weren't omitted when it checked the header (pure guesswork on that).

  


  So, is there a way to copy ONLY the video, regardless of whatEVER tracks may or not be in the file, then do the same for audio, and then merge the two single-track files ?