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• When creating ffmpeg segments instead of "-t" I cannot move inside the resulting MP4 file [closed]

  2 mai 2024, par pavlii

  We are using ffmpeg for grabbing X11 session and we had changed a bit the commant run. I will write only the different part of the command ; the rest were maintained so are not important for this problem :

  


  ffmpeg ..... -t 00:14:58 (old command)

  


  ffmpeg ..... -f segment -segment_time 900 -strftime 1 (new command)

  


  Resulting files are (in both cases) MP4. But in new - using segments - variant I am able to open the file in VLC player as usual but I cannot do any location inside. So I have to wait for example 700s to see what had happened at that time - I cannot use VLC slider to muve to that position.

  


  I am sure there is parametric solution I cannot find out yet :-)

  


  Many thanx for any ideas ; in case of further details no problem to add them.

  


  Regards, Pavel

  


  I am just browsing internet whether I find any tip for possible solution. I expected the behaviour like before, i.e. to be able to move to any location in resulting MP4 file when played back.

  


• ffmpeg - data is being "removed" while h264 is being processed by ffmpeg

  21 mai 2024, par Laki

  I got a file which is created based on messages coming from streaming, all of the "messages" are ending with b'h264\x00'
I got a need to

  


  

  • load the data into ffmpeg

  


  • perform some processing of the data

  


  • re-attach the data to same "messages"

  


  


  Data is loaded with ffmpeg and saved with ffmpeg - however - ffmpeg removes "part" of the data
I have simplified the process and currently I am only loading and saving the data, without any processing, but still - part of the data is being removed

  


  I have used several commands - but always, part of my data is being removed

  


  ffmpeg -i sthg3.h264  -c copy st3.h264
ffmpeg  -err_detect ignore_err -i sthg3.h264  -c copy st3.h264
ffmpeg -fflags +genpts -i sthg3.h264 -c copy st3.h264 


  


  I have created the script for calculating that

  


  file_out = 'sthg3.h264'
def split_file(input_file,chunki):
    output_files = []
    with open(input_file, 'rb') as f:
        file_number = 0
        while True:
            chunk = f.read(504096)  # Read a chunk of data
            if not chunk:  # End of file
                break
            index = chunk.find(chunki)  # Find the delimiter
            while index != -1:
                chunk = chunk[index+len(chunki):]
                file_number += 1
                index = chunk.find(chunki)  # Find the next delimiter
    return file_number

chunki = b'h264\x00'
print(split_file(file_out,chunki))
chunki = b'\x00\x01\x00'
print(split_file(file_out,chunki))
    
chunki = b'h264\x00'
#chunki = b'\x00\x00\xdc\x9e'
print(split_file('st3.h264',chunki))
chunki = b'\x00\x01\x00'
print(split_file('st3.h264',chunki))


  


  and here is the question, how to push data through ffmpeg to avoid removing data, or replace it with something that would not be removed ?

  


• the "non-monotonic DTS in output stream " error while concatenation even after reencoded input files

  19 juin 2024, par nish

  hi I am trying to write a Python program that is trying to first edit different videos separately under the heading "intro" "story" and "byte" with the help of FFmpeg and Python subprocess module and then concatenate them in the function named "bind". At first, I encountered this "Non-monotonic DTS in output stream" then i reencoded the input files before concatenating them but i am still getting this error

  


  # function to assemble all the videos 


  


  def bind() :

  


  bunch = ["final_intro.mp4","final_story.mp4","finalbite.mp4"]
new_bunch =[]
for video in bunch:
    name = f"re_{video}"
    re_command =[
        "ffmpeg", "-y",
        "-i", video,
        "-c:v", "libx264",
        "-c:a", "aac",
        "-strict", "experimental",
        "-b:a", "192k",
        name
    ]
    subprocess.run(re_command)
    new_bunch.append(name)
    

with open("concat_list_final.txt", "w") as f:
    for video in new_bunch:
        f.write(f"file './{video}'\n")
  
command_final = [ 
    "ffmpeg", "-y",
    "-f", "concat",
    "-safe", "0",
    "-i", "concat_list_final.txt",
    "-c", "copy",
    "done.mp4"
]
subprocess.run(command_final)
for video in new_bunch:
    os.remove(video)
os.remove("final.mp4")
os.remove("updated_final.mp4")
os.remove("concat_list_final.txt")


return "done.mp4"


  


  for reference this is the error messages :-

  


  [mov,mp4,m4a,3gp,3g2,mj2 @ 0x14cf16040] Auto-inserting h264_mp4toannexb bitstream filter [mp4 @ 0x12ce06880] Non-monotonic DTS in output stream 0:0 ; previous : 152933, current : 127760 ; changing to 152934. This may result in incorrect timestamps in the output file. [mp4 @ 0x12ce06880] Non-monotonic DTS in output stream 0:0 ; previous : 152934, current : 128272 ; changing to 152935. This may result in incorrect timestamps in the output file..........