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• ffmpeg uses all images in a folder even with a -start_number argument

  13 décembre 2013, par kingds

  I'm having trouble compiling a set of jpeg files in a directory into an mp4 file. The command I'm using is :

  ./ffmpeg -y -r 20 -i %03d-capture.jpg -pix_fmt yuv420p -c:v libx264 -start_number 10000 video.mp4

  The folder contains around 20,000 images, and I want a video that starts on the 10,000th image. However, with this command ffmpeg creates a video using all the images in the directory. Is there any reason it would be ignoring the start_number argument ?

  edit : Figured it out. The -start_number argument needs to come before the -i argument for the input file. Seems a little silly.

• ffmpeg Ghosting between RGB color channels [closed]

  24 mai 2024, par Blikpils

  This seems like a very specific question so i hope there is someone who can help me out.
Within FFMPEG i am trying to add (channel pack) 3 different grayscale videos in RGB within a webm or mp4 video. I got it to work to a degree via Merge planes.
This is what i tried :

  


  ffmpeg -y -i video1.webm -i video2.webm -i video3.webm -filter_complex "[0:v]format=gray[r]; [1:v]format=gray[g]; [2:v]format=gray[b]; [g][b][r]mergeplanes=0x001020:format=gbrp" -pix_fmt yuv420p -t 00:00:03 output.webm


  


  This is the result :


  


  As you see the 9 is visible in the red and blue channel and so are each of the other channels

  


  I have tried just extracting a single channel in a video, change the compression change the format change the color space, make sure that its all linear but each seem to have the limitation of some smearing/artifacts between the other channels.

  


  Is it at all possible to add different grayscale streams in the color channels without any artifacts and if so in which direction should i look ?

  


  Any help would be greatly appreciated !

  


• Convert ogg byte array to wav byte array Python

  2 février 2023, par Ramish Rasool

  I want to convert ogg byte array/bytes with Opus codec to wav byte array/bytes without saving to disk. I have downloaded audio from telegram api and it is in byte array format with .ogg extension. I do not want to save it to filesystem to eliminate filesystem io latencey.

  


  Currently what I am doing is after saving the audio file in .ogg format using code the below code using telegram api for reference https://docs.python-telegram-bot.org/en/stable/telegram.file.html#telegram.File.download_to_drive

  


  # listen for audio messages
async def audio(update, context):
    newFile = await context.bot.get_file(update.message.voice.file_id)
    await newFile.download_to_drive(output_path)


  


  I am using the code

  


  subprocess.call(["ffmpeg", "-i", output_path, output_path.replace(".ogg", ".wav"), '-y'], stderr=subprocess.DEVNULL, stdout=subprocess.DEVNULL)


  


  to convert ogg file to wav file. But this is not what I want.

  


  I want the code

  


  async def audio(update, context):
    newFile = await context.bot.get_file(update.message.voice.file_id)
    byte_array = await newFile.download_as_bytearray()


  


  to get byte_array and now I want this byte_array to be converted to wav without saving to disk and without using ffmpeg. Let me know in comments if something is unclear. Thanks !

  


  Note : I have setted up a telegram bot at the backend which listens for audios sent to private chat which I do manually for testing purposes.