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• How to get the last x seconds with high accuracy with FFmpeg ?

  16 novembre 2024, par rbarab

  I would like to batch process mp4 videos, getting the last x seconds of each and saving them to individual files.
I need to do this with a very high accuracy, preferably to 0.001 seconds or better.
Found a related question (FFmpeg : get the last 10 seconds) suggesting -sseof, which works great, but as the answer said it's not completely accurate with stream copy.

  


  I am trying to match video lengths to the length of a reference video.

  


  Would I need to re-encode ? Can sseof handle this accurate enough if I specify duration as 00:00:00.000000 (which I get from reference video ffprobe) ?

  


  Please see related ffprobe -i below, all videos to be processed have this same encoding.

  


     Metadata:
    major_brand     : isom
    minor_version   : 512
    compatible_brands: isomiso2avc1mp41
    encoder         : Lavf57.83.100
  Duration: 00:00:58.67, start: 0.000000, bitrate: 639 kb/s
    Stream #0:0(und): Video: h264 (High) (avc1 / 0x31637661), yuv420p, 640x360, 499 kb/s, 29.97 fps, 29.97 tbr, 30k tbn, 59.94 tbc (default)
    Metadata:
      handler_name    : VideoHandler
    Stream #0:1(und): Audio: aac (LC) (mp4a / 0x6134706D), 48000 Hz, stereo, fltp, 131 kb/s (default)
    Metadata:
      handler_name    : SoundHandler
duration=58.673000


  


  Is there a better way to achieve frame-level accuracy ? As end goal I would need to overlay these videos with 25fps 'frame-level accuracy'.

  


• ffmpeg specify image start/end time by seconds in slideshow

  31 décembre 2022, par Martin

  I have an ffmpeg command that when ran on command prompt in win10, will combine 2 mp3 files and 1 image file into a low resolution .mkv video file.

  


  06:23 = 383 = song1.mp3 length
05:40 = 340 = song2.mp3 length
12:03 = 723 = estimated total video length
12:04 = 724 = actual video length


  


  Command that generates video file :

  


  ffmpeg -loop 1 -framerate 2 -i images/img1.png  -i "audio files/song1.mp3"  -i "audio files/song2.mp3"  -c:a pcm_s32le  -filter_complex concat=n=2:v=0:a=1  -vcodec libx264  -bufsize 3M  -filter:v "scale=w=640:h=638,pad=ceil(iw/2)*2:ceil(ih/2)*2"  -crf 18  -pix_fmt yuv420p  -shortest  -tune stillimage  -t 724 audioAndImageIntoVideo.mkv 


  


  The current command just uses -i images/img1.png as a static image for the entire video. But I want to have one image for the duration of the first song, and a second image for the duration of the second song. With a timeline like so :

  


  song1.mp3 and img1.png start at 00:00 and end at 06:23 ( 383 seconds )
song2.mp3 and img2.png start at 06:23 ( 383 seconds ) and end at 12:03 ( 723 seconds )


  


  is there any flag to specify the timeline of two images ? Right now I am just trying to get them in order in a video, and then I can change the individual img resolution / size / stretching details for how it fills the frame

  


• Processing video frame by frame in AWS Lambda with Node.js and FFmpeg [closed]

  29 décembre 2023, par Aviato

  I am working on a project where I need to process video frames one at a time in an AWS Lambda function using Node.js. My goal is to avoid storing all frames in memory or the filesystem due to resource constraints. I plan to use the fluent-ffmpeg library or ffmpeg from child processes for video processing.

  


  In the past, I used OpenCV to process videos and frames without writing the frames on the disk or storing all the frames at once on the memory itself. But now as I am using node js, its a little hard to set up the code using ffmpeg, etc.

  


  Here is a small snippet from what I did with opencv :-

  


  import cv2

cap = cv2.VideoCapture(video_file)

out = cv2.VideoWriter('output.mp4', fourcc, fps, (width, height))

def generate_frame():
        while cap.isOpened():
            code, frame = cap.read()
            if code:
                yield frame
            else:
                print("completed")
                break

for i, frame in enumerate(generate_frame()):
          # Now we can process the video frames directly and write them on the output opencv
          out.write(editing_frames)


  


  Additionally, I intend to leverage image processing libraries like Sharp and the Canvas API to edit individual frames before assembling the final video. I am looking for help in handling video frames efficiently within the constraints of AWS Lambda.

  


  Any insights, code snippets, or recommendations would be greatly appreciated. Thank you !