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• "fixing" RTL texts from logical to visual, before embedding in video as subtitles with ffmpeg

  13 mai 2024, par Berry Tsakala

  I'm searching for the correct way to pre-process my subtitles files before hard-coding them into video clips.

  


  Currently, ffmpeg does not process RTL (right-to-left) languges properly ; I have detailed the problem here :
https://superuser.com/questions/1679536/how-to-embed-rtl-subtitles-in-a-video-hebrew-arabic-with-the-correct-lan

  


  However, there could be 2 programmatic solutions :

  


  

  1. adding certain unicode control characters can fix (or partially fix) the text, which is then fed into ffmpeg, giving good results.

  


  


  

  • character 0x200F at the end of a hebrew clause, after punctuation

  


  • character 0x202B, I haven't yet learned its usage.

  


  


  

  2. I can edit the text so that it will produce the correct results on ffmpeg.
But that requires smart BiDi algorithm.

  


  


  Do you know how to preprocess such text ?

  


  (this is NOT an encoding question. It is about RTL/LTR algorithm to use.)

  


  Thank you

  


• Download from YouTube as ".wav" instead of ".webm"

  11 août 2022, par Bastian Gerjol

  I am trying to extract an audio from a YouTube Video as an .wav file.
However, the script that I am running keeps giving me .webm files.
The code I am using is the following :

  


  from __future__ import unicode_literals
import youtube_dl

ydl_opts = {
    'format': 'bestaudio/best',
    'postprocessors': [{
        'key': 'FFmpegExtractAudio',
        'preferredcodec': 'wav',
        'preferredquality': '192'
    }],
    'postprocessor_args': [
        '-ar', '16000'
    ],
    'prefer_ffmpeg': True,
    'keepvideo': True
}

with youtube_dl.YoutubeDL(ydl_opts) as ydl:
    ydl.download(['https://www.youtube.com/watch?v=2Xq7iJKzhR4'])


  


  Is there a way to change the output and keep the highest possible audio quality ?

  


  I tried setting prefer_ffmpeg': True to False & keepvideo': True to False but that did not change anything.

  


  I would appreciate suggestions and please keep in mind that I never used Python before.

  


• ffmpeg throws "cur_dts is invalid" error when trying to get stream from IP camera

  17 octobre 2022, par Max

  I'm trying to stream from an IP camera with the following ffmpeg command :

  


  const command = [
        '-loglevel',
        'debug',
        '-timeout',
        '10000000',
        '-rtsp_transport',
        'tcp',
        '-i',
        this.cameraInfo.url,
        '-c:v',
        'copy',
        '-c:a',
        'aac',
        '-f',
        'mp4',
        '-movflags',
        '+faststart+frag_every_frame+empty_moov+default_base_moof',
        "-min_frag_duration",
        this.livestreamSegmentDuration,
        'pipe:1',
    ];


  


  With this command I pass an output to another stream transformer and stream as HLS using "mp4" instead of "ts" to avoid transcoding.

  


  Everything works smoothly with different cams, but when I try to get the stream from "Meldana" (issue is related to all ip cameras of this manufacturer), it constantly throws the following error and does not stream :

  


  cur_dts is invalid st:0 (0) [init:1 i_done:0 finish:0] (this is harmless if it occurs once at the start per stream)
cur_dts is invalid st:1 (0) [init:0 i_done:0 finish:0] (this is harmless if it occurs once at the start per stream)
cur_dts is invalid st:0 (0) [init:1 i_done:0 finish:0] (this is harmless if it occurs once at the start per stream)
cur_dts is invalid st:1 (0) [init:0 i_done:0 finish:0] (this is harmless if it occurs once at the start per stream)
cur_dts is invalid st:0 (0) [init:1 i_done:0 finish:0] (this is harmless if it occurs once at the start per stream)
cur_dts is invalid st:1 (0) [init:0 i_done:0 finish:0] (this is harmless if it occurs once at the start per stream)
cur_dts is invalid st:0 (0) [init:1 i_done:0 finish:0] (this is harmless if it occurs once at the start per stream)
cur_dts is invalid st:1 (0) [init:0 i_done:0 finish:0] (this is harmless if it occurs once at the start per stream)
cur_dts is invalid st:0 (0) [init:1 i_done:0 finish:0] (this is harmless if it occurs once at the start per stream)
cur_dts is invalid st:1 (0) [init:0 i_done:0 finish:0] (this is harmless if it occurs once at the start per stream)
cur_dts is invalid st:0 (0) [init:1 i_done:0 finish:0] (this is harmless if it occurs once at the start per stream)
cur_dts is invalid st:1 (0) [init:0 i_done:0 finish:0] (this is harmless if it occurs once at the start per stream)
cur_dts is invalid st:0 (0) [init:1 i_done:0 finish:0] (this is harmless if it occurs once at the start per stream)
cur_dts is invalid st:1 (0) [init:0 i_done:0 finish:0] (this is harmless if it occurs once at the start per stream)


  


  Even though it does not work with ffmpeg, I can watch the stream just fine in VLC.
What might be the problem ? Is there anything that could be corrected in the ffmpeg command ?