Recherche avancée

Sur d’autres sites (14120)

• FFMPEG concat leaves audio gapes between clips

  14 novembre 2022, par GotCubes

  I'm writing a python script that uses subprocess to invoke FFMPEG, not using pyffmpeg.

  



  My script generates a variable number of MP4 files using the AAC audio codec, and concatenates them together using FFMPEG. Here is how I'm constructing each clip :

  



  ffmpeg -loop 1 -i image.jpg -i recording.mp3 -tune stillimage -c:a aac -b:a 256k -shortest clip.mp4


  



  The command I'm using to concatenate them is :

  



  ffmpeg -f concat -i clip_names.txt -c copy video_raw.mp4


  



  I then take that resulting video, and mix a looping audio track over it, and adjust the volume. (Sorry for the awful formatting)

  



  ffmpeg -i video_raw -filter_complex
                 "amovie=Tracks/Breaktime.mp3:loop=0,
                  volume=0.1,
                  asetpts=N/SR/TB[aud];
                  [0:a][aud]amix[a]"
-map 0:v -map [a] -b:a 256k -shortest final_video.mp4


  



  These commands seem to work as I intend them to. When I play the resulting MP4 from my local machine, everything plays without issue.

  



  However, I uploaded the video to YouTube, and ran into issues. When the video is played from YouTube, there is about a second of silence at every timestamp where two clips were concatenated, before the next clip begins. I've tried this from Chrome, IE, and Firefox, all with the same issues.

  



  Based on what I've looked into so far, I think it could be an issue with how the priming samples of each individual clip are handled. I'm not obligated to keep using MP4 or AAC, so if using a different audio/video codec would work better, feel free to suggest !

  



  Is there some type of manipulation I can do in FFMPEG to get rid of the priming samples, or somehow process them differently ? In the end, I'm looking for each clip to play back to back without the delay that the concat operation seems to insert. Thank you !

  


• How to make WebM screen recording chunks independently processable for audio with FFmpeg ?

  3 décembre 2024, par Dinesh Kumar

  I am streaming screen recordings from the browser into 5-second WebM chunks using the MediaRecorder API. The first chunk (root chunk) is independently processable because it contains the necessary EBML headers and metadata. However, subsequent chunks are not independently processable, as they lack the required metadata, which prevents me from extracting audio independently from them.

  


  I am unable to extract audio independently from the individual chunks using FFmpeg due to missing headers, resulting in errors like EBML header parsing failed. The first chunk works fine on its own, but the subsequent chunks also need to be processed independently for audio extraction.

  


  I am looking for a solution using FFmpeg to fix these chunks so that I can extract audio independently from each chunk.

  


  

  1. Is there a way to repair these chunks post-recording with FFmpeg to include the missing metadata and headers, making them independently processable for audio extraction ?

  


  2. Can FFmpeg reinitialize the EBML headers in each chunk, or is there a command that can add the metadata from the first chunk to subsequent chunks to allow for independent audio extraction ?

  


  


  Additionally, should I consider any changes in the MediaRecorder API to ensure that the chunks are properly formatted for independent processing ? The goal is to make each WebM chunk fully independent, allowing me to extract audio independently from each chunk.

  


• What does FFmpeg expect me to send to the first rawvideo input pipe ?

  23 octobre 2023, par Somebody

  I'm using two named pipes, in order :

  


  

  1. video_pipe


     -f rawvideo
-video_size 1x1
-pix_fmt gray
-r 1


     


  


  2. audio_pipe


     -f s16le
-ar 32000
-channels 1


     


  


  


  I thought FFmpeg needed to read individual frames from a rawvideo pipe but I must be mistaken cause it doesn't start reading from the second pipe until I feed 11 bytes to the first pipe although, in the example given, a grayscale frame of one pixel is exactly one byte. I have experimenting by increasing video_size and here's the table I could infer :

  


  





  


  


  


  


  



  


  


  


  


  


  


  


  


  


  


  


  


  


  


  


  


  


  


  


  


  


  


  


  


  Actual frame size in bytes	Bytes needed to be sent before to move on
  1	11
  2	17
  3	25
  4	33
  5	41
  6	49

  


  


  I can't just send multiple frames as I want to output a 1 second video.
I tested most of the parameters in this page : https://github.com/FFmpeg/FFmpeg/blob/ff5a3575fec2d49d5fae4ec1198a939e203314db/libavformat/options_table.h
but none of them solved it. (I also used "-re" with no luck).

  


  This is an example command in case you want to reproduce the issue :
ffmpeg -y -re -f rawvideo -video_size 1x1 -pixel_format gray -framerate 1 -i \\.\pipe\video_pipe -f s16le -ar 32000 -channels 1 -i \\.\pipe\audio_pipe -map 0:v:0 -map 1:a:0 out.mp4

  


  Any idea of how I could send the exact frame bytes amount instead of being forced to send way more bytes ?