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• cv2/ffmpeg "grabFrame packet read max attempts exceeded" error after exactly reading certain number of frames

  26 juin, par banjaxing

  I am using OpenCV to extract frames from videos, run a segmentation AI model, and save the frames and masks to a folder. When I run my code to extract the frame from I encounter the error "grabFrame packet read max attempts exceeded" after processing a certain number of frames. This issue occurs consistently for the same videos across multiple environments.

  


  Error message :

  


  [ WARN:0@379.898] global cap_ffmpeg_impl.hpp:1541 grabFrame packet read max attempts exceeded, if your video have multiple streams (video, audio) try to increase attempt limit by setting environment variable OPENCV_FFMPEG_READ_ATTEMPTS (current value is 10000)


  


  Minimum Reproducible Example

  


  import os
import cv2

videofilename = "test.mp4"
capture = cv2.VideoCapture(videofilename)
frameNum = 0

createfolder = os.getcwd() + '/' + videofilename.split(".")[0] + '/'
if not os.path.exists(createfolder):
    os.makedirs(createfolder)
    os.makedirs(createfolder + "/frames/")

while True:
    success, frame = capture.read()
    if success is False:
        break
    frameNum += 1
    framedownloadname = videofilename.split(".")[0] + '-fr' + str(frameNum) + '.jpg'
    framedownloadloc = createfolder + '/frames/' + framedownloadname
    print(framedownloadloc)
    cv2.imwrite(framedownloadloc, frame)
    img = cv2.imread(framedownloadloc)
    img = cv2.cvtColor(img, cv2.COLOR_BGR2RGB)

capture.release()


  


  As suggested in error, I increased the OPENCV_FFMPEG_READ_ATTEMPTS env variable up to 10000. However, this seems to have little to no effect on the number of frames before the error appears.

  


• 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..........

  


• FFmpeg error with ffmpeg.FS("readfile", "output.mp4"). trying to get ffmpeg to work in the react app

  21 juin 2024, par Paul Tham

   const stackVideos = useCallback(
    async (video1) => {
      try {
        console.log("Fetching video2 from storage...");
        const video2Ref = ref(storage, "video2.mp4");
        const video2Url = await getDownloadURL(video2Ref);
        const video2Blob = await (await fetch(video2Url)).blob();

        console.log("Writing video1 to FFmpeg FS...");
        await ffmpeg.FS("writeFile", "video1.mp4", await fetchFile(video1));

        console.log("Writing video2 to FFmpeg FS...");
        await ffmpeg.FS("writeFile", "video2.mp4", await fetchFile(video2Blob));

        console.log("Files in FFmpeg FS after write:");
        const files = await ffmpeg.FS("readdir", "/");
        console.log(files);

        const { start, end } = inputs[0];
        const startSeconds = new Date(`1970-01-01T${start}Z`).getTime() / 1000;
        const endSeconds = new Date(`1970-01-01T${end}Z`).getTime() / 1000;
        const duration = endSeconds - startSeconds;

        console.log("Running FFmpeg command...");
        await ffmpeg.run(
          "-i",
          "video1.mp4",
          "-ss",
          startSeconds.toString(),
          "-t",
          duration.toString(),
          "-i",
          "video2.mp4",
          "-filter_complex",
          "[0:v]scale=1080:-1[v1];[1:v]scale=-1:1920/2[v2scaled];[v2scaled]crop=1080:1920/2[v2cropped];[v1][v2cropped]vstack=inputs=2,scale=1080:1920[vid]",
          "-map",
          "[vid]",
          "-map",
          "0:a",
          "-c:v",
          "libx264",
          "-crf",
          "23",
          "-preset",
          "veryfast",
          "-shortest",
          "output1.mp4"
        );

        console.log("Files in FFmpeg FS after run:");
        const filesAfterRun = await ffmpeg.FS("readdir", "/");
        console.log(filesAfterRun);

        console.log("Reading output1.mp4 from FFmpeg FS...");
        const data = await ffmpeg.FS("readfile", "output1.mp4");
        console.log("after the FS readfile");
        const url = URL.createObjectURL(
          new Blob([data.buffer], { type: "video/mp4" })
        );
        setStackedVideo(url);
        setOutputFileReady(true); // Mark output file as ready
      } catch (err) {
        console.error("FFmpeg error output:", err);
        setError(`FFmpeg run error: ${err.message}`);
        setIsProcessing(false);
      }
    },
    [inputs]
  );


  


  My error seems to be stemming from this line :

  


   const data = await ffmpeg.FS("readfile", "output1.mp4");


  


  Seeing the ffmpeg.wasm documentation i thought the functions for some of the functions had changed, but when I changed it, it seemed like they did not recognise the new functions. Sometimes this will also give me some other errors like worker.js which I dont understand enough to debug this myself.

  


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