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• Finding corrupted videos with python

  16 septembre 2022, par tusker

  I have huge video dataset (about 500000 16 frame length clips). Some of the videos produce messages like

  


  [mpeg4 @ 0x561b46a44b80] marker does not match f_code
[mpeg4 @ 0x561b480c0740] Error at MB: 4718
[mpeg4 @ 0x561b4811b640] header damaged


  


  I want to find which videos cause the problem.
  
First I tried with this https://superuser.com/questions/100288/how-can-i-check-the-integrity-of-a-video-file-avi-mpeg-mp4 solution, but I got nothing in the error files.

  


  My second idea was to read the first image of a video and if it throws an error, save the filename to a file. However, it seems this is not an error message : although the messages appeared on console, read returned with success=True.

  


  Then I tried to print the filenames to standard error (where the warning messages also go), saving it to a file and do some postprocessing to extract the videos which has problem.

  


  import os
from tqdm import tqdm
import sys

folder = '/path/to/videos'
for f in tqdm(os.listdir(folder)):
  sys.stderr.write('BEFORE VIDCAP ' + f + '\n')
  vidcap = cv2.VideoCapture(os.path.join(folder,f))
  sys.stderr.write('BETWEEN VIDCAP AND SUCCESS' + f + '\n')

  success, image = vidcap.read()
  sys.stderr.write('AFTER SUCCESS ' + f + '\n')


  


  However, the standard error outputs in the following order :

  


  AFTER SUCCESS
[mpeg ...] 
[mpeg ...]
...
BEFORE VIDCAP


  


  It doesn't make sense how can it happen in this order, some broken videos should be seen somewhere between BEFORE and AFTER. (And the ones following or preceding are not broken neither if I try to open them individually.)

  


  My last idea was to create for every video a file, making it as the stderr and check the non-empty files. (I know it's insanely inefficient, but I didn't have any other idea.)

  


  for f in os.listdir(folder):
  sys.stderr = open(f + '.txt', 'w')
  vidcap = cv2.VideoCapture(os.path.join(folder,f))
  success, image = vidcap.read()


  


  This doesn't work also, all the error files are empty, although the messages still appear on standard error.

  


  ---

  


  So my questions are the following :

  


  

  1. What would be an efficient solution for this problem ?

  


  2. How is this order of outputs (first code example) possible ? There is some parallelism under the hood ?

  


  3. Where are this messages going if not to the standard error (second code example) ? If yes, why are they printed to the console instead of the specified error file ?

  


  


• FFmpeg on Qt Creator

  10 novembre 2022, par c47296

  I have got FFmpeg compiled using MSYS2. I have a strange issue that appeared only recently.the app crashes.
This is my main file :

  


  #include "mainwindow.h"&#xA;#include <qapplication>&#xA;#include <qdebug>&#xA;&#xA;extern "C" {&#xA;#include <libavdevice></libavdevice>avdevice.h>&#xA;#include <libavformat></libavformat>avformat.h>&#xA;#include <libavutil></libavutil>avutil.h>&#xA;#include <libavcodec></libavcodec>avcodec.h>&#xA;}&#xA;&#xA;&#xA;int main(int argc, char *argv[])&#xA;{&#xA;   //qDebug() &lt;&lt; av_version_info();&#xA;  // avdevice_register_all();&#xA;    QApplication a(argc, argv);&#xA;    MainWindow w;&#xA;    w.show();&#xA;    return a.exec();&#xA;}&#xA;</qdebug></qapplication>

  


  The program runs but crashes if I call 'avdevice_register_all()' and others FFmpeg functions，but only call 'av_version_info()' is runs, not crashes.
I don't really know how to solve this ?

  


  I have already tried to use google solving the problem,but no result.

  


• In what way does this HEVC video not comply to Apples's requirements document ?

  16 novembre 2022, par Duke Dougal

  My goal is to work out why a given video file does not play on Macos/Safari/Quicktime.

  


  The background to this question is that it is possible to play HEVC videos with a transparent background/alpha channel on Safari/MacOS. To be playable, a video must meet the specific requirements set out by Apple in this document :

  


  https://developer.apple.com/av-foundation/HEVC-Video-with-Alpha-Interoperability-Profile.pdf

  


  The video that does not play on Apple/Safari/Quicktime is an HEVC video with an alpha transparency channel. Note that VLC for MacOS DOES play this file. Here it is :

  


  https://drive.google.com/file/d/1ZnXjcDbk-_YxTgRuH_D7RSR9SXdY_XTv/view?usp=share_link

  


  I have two example HEVC video files with a transparent background/alpha channel, and they both play fine using either Quicktime player or Safari :

  


  Working video #1 :

  


  https://drive.google.com/file/d/1PJAyg_sVKVvb-Py8PAu42c1qm8l2qCbh/view?usp=share_link

  


  Working video #2 :

  


  https://drive.google.com/file/d/1kk8ssUyT7qAaK15afp8VPR6mIWPFX8vQ/view?usp=sharing

  


  The first step is to work out in what way my non-working video ( https://drive.google.com/file/d/1ZnXjcDbk-_YxTgRuH_D7RSR9SXdY_XTv/view?usp=share_link ) does not comply with the specification.

  


  Once it is clear which requirements are not met by the non-working video then I can move onto the next phase, which is to try to formulate an ffmpeg command that will output a video meeting the requirements.

  


  I have read Apples requirements document and I am out of my depth in trying to analyse the non working video against the requirements - I don't know how to do it.

  


  Can anyone suggest a way to identify what is wrong with the video ?

  


  Additional context is that I am trying to find a way to create Apple/MacOS compatible alpha channel / transparent videos using ffmpeg with hevc_nvenc running on an Intel machine. I am aware that Apple hardware can create such videos, but for a wide variety of reasons it is not practical for me to use Apple hardware to do the job. I have spent many hours trying all sorts of ffmpeg and ffprobe commands to try to work out what is wrong and modify the video to fix it, but to be honest most of my attempts are guesswork.