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• Difference between single and double quotes in subprocess [Python 3.4]

  11 décembre 2016, par Vasilis

  I’m using Python 3.4 in Windows Server 12 and I have some Python code that executes the ffmpeg command bellow :

  ffmpeg -i input.mp4 -vf select='not(mod(n\,30)),setpts=N/((30)*TB)' -c:v rawvideo  -pix_fmt uyvy422 -y output.avi

  I use the following code to execute the external command :

  try:
  
      output = subprocess.check_output(command, stderr=subprocess.STDOUT, shell=True)
  
  except subprocess.CalledProcessError as exc:
  
      print ("Command %s failed with error code" % command, exc.returncode, exc.output, file=sys.stderr)

  When I pass the command enclosed in single quotes it successfully runs the command :

  command = 'ffmpeg -i input.mp4 -vf select="not(mod(n\,30)),setpts=N/((30)*TB)" -c:v rawvideo  -pix_fmt uyvy422 -y output.avi'

  When I pass the command as a string enclosed in double quotes it fails :

  command = "ffmpeg -i input.mp4 -vf select='not(mod(n\,30)),setpts=N/((30)*TB)' -c:v rawvideo  -pix_fmt uyvy422 -y output.avi"

  The error message is the following :

  [Eval @ 0000000eaf2fe040] Invalid chars ',setpts=N/((30)*TB)' at the end of expression 'not(mod(n,30)),setpts=N/((30)*TB)'  
  
  [Parsed_select_0 @ 0000000eb0d27ca0] Error while parsing expression 'not(mod
  
  (n,30)),setpts=N/((30)*TB)'  
  
  [AVFilterGraph @ 0000000eb0d0a5a0] Error initializing filter 'select' with args 'not(mod(n\\,30)),setpts=N/((30)*TB)'  
  
  Error opening filters!"

  So it appears that when using double quotes the slash / that is part of the setpts=N/((30)*TB) option is not interpreted correctly, while with double quotes there’s no problem. Note that both commands (either with double or single quotes in the select option) work fine when I run them directly from the command prompt.
  However, I’ve seen many people saying that from a technical perspective single and double quotes make no difference, e.g.

  • http://programmers.stackexchange.com/questions/155176/single-quotes-vs-double-quotes
  • http://programmers.stackexchange.com/questions/155176/single-quotes-vs-double-quotes

  Does slash parsing depend on the quotes around the string or this is just a behavior specific to the executable I’m running ?

• Making a movie out of pictures in correct order

  6 novembre 2022, par astrogab

  Short version

  


  How can one combine files img1000.png, img5000.png, img10000.png, img11000.png in the right order into a movie ?

  


  Longer version

  


  I am using ffmpeg to make a movie out of snapshots of a simulation. There should be for instance 5 images per second. The names are :

  


  image0200.png
image0300.png
image0400.png
image0500.png
image1000.png
image1500.png
image2000.png
...
image8500.png
image9000.png
image9500.png
image10000.png
image15000.png


  


  i.e., they are sequential but there are irregular gaps in the numbers. The numbers are formatted according to '%04d' but go above 9999. I have tried

  


  ffmpeg -y -loglevel debug -nostats \
-r:v 5 -thread_queue_size 1024 -f image2 \
-pattern_type glob -i "*[0-9][0-9][0-9][0-9].png" \
-r:v 30 -preset veryslow -pix_fmt yuv420p -crf 28 \
-an  AMDG.mp4


  


  and many, many other variations but either only two frames end up being visible in the movie (even though the images are found when using -debug) or only the files up to image9500.png are used (and glob does not seem to allow [0-9]{4,} as for regex), or, with

  


      ffmpeg -y -loglevel debug -nostats \
    -r:v 5 \
    -thread_queue_size 1024 -f image2 -pattern_type glob \
       -i "image[0-9][0-9][0-9][0-9].png" \
    -r:v 5 \
    -thread_queue_size 1024 -f image2 -pattern_type glob \
       -i "image[1-9][0-9][0-9][0-9][0-9].png" \
    -r:v 30 -preset veryslow -pix_fmt yuv420p -crf 28 \
    -map 0 -map 1 \
    -an  AMDG.mp4


  


  there are apparently two streams in the output movie and only one of them is being played. (I realised in the process -map 0 -map 1 was needed in order for both input streams to be used.)

  


  In one of the variations of options I found (now I have lost what it was exactly !) all images were included but the order was not the desired one : image1000.png was shown before image10000.png. Apparently a newer version of ffmpeg (I have ffmpeg version 3.4.8-0ubuntu0.2) has the ability to sort like sort -V, so that image10000 come after image1000, but reinstalling ffmpeg is in general not a practical option. Also renaming the files is not practical and creating e.g. soft links with sequential names in the format '%05d' starting at 0 and in steps of 1 (so that -i '%05d' could be used) is of course not elegant.

  


  With the -concat filter as in https://unix.stackexchange.com/questions/77016/ffmpeg-pattern-type-glob-not-loading-files-in-correct-order, i.e.,

  


    ffmpeg -y -loglevel debug -nostats -r:v 5 \
    -thread_queue_size 1024 -f image2 -f concat \
    -safe 0 -i <(find . -maxdepth 1 -regex 'image*.png' \
       -exec echo "file $(pwd)/"{} \; | sort -V) \
    -r:v 30 -codec:v libx264 -preset veryslow -pix_fmt yuv420p -crf 28 \
    -an \
    AMDG.mp4


  


  the processing took a long time and made the whole system sluggish, while producing a movie of 60 kB showing only two different images.

  


  I have the impression that there are several issues at once... Thanks if you can help !

  


• CJEU rules US cloud servers don’t comply with GDPR and what this means for web analytics

  17 juillet 2020, par Jake Thornton
  Breaking news : On July 16, 2020, the Court of Justice of the European Union (CJEU) has ruled that any cloud services hosted in the US are incapable of complying with the GDPR and EU privacy laws.

  In August 2016, the EU-US Privacy Shield framework came into effect, which “protects the fundamental rights of anyone in the EU whose personal data is transferred to the United States for commercial purposes. It allows the free transfer of data to companies that are certified in the US under the Privacy Shield.” – European Commission website

  However after today’s CJEU ruling, this Privacy Shield framework became invalidated due to significant differences between EU and US privacy laws.

  European privacy law activist Max Schrems summarises with “The Court clarified for a second time now that there is a clash between EU privacy law and US surveillance law. As the EU will not change its fundamental rights to please the NSA, the only way to overcome this clash is for the US to introduce solid privacy rights for all people – including foreigners. Surveillance reform thereby becomes crucial for the business interests of Silicon Valley.” – noyb website

  Today’s ruling also continues to spark concern into the legitimacy of US privacy laws which doesn’t fully protect people’s personal data when hosted on cloud servers based in the US.

  

  How will this affect you ?

  For any business operating a website in the EU or if you have traffic coming to your website from EU visitors, you need to know what data you’re capturing and where this data is being stored.

  Here’s what Maja Smoltczyk (Berlin’s Commissioner for Data Protection and Freedom of Information) says :

  Controllers who transfer personal data to the USA, especially when using cloud-based services, are now required to switch immediately to service providers based in the European Union or a country that can
  ensure an adequate level of data protection. The CJEU has made it refreshingly clear that data exports are not just financial decisions, as people’s fundamental rights must also be considered as a matter of priority. This ruling will put
  an end to the transfer of personal data to the USA for the sake of convenience or to cut costs.

  The controller is you (not Google) and by transferring data to the US you are at risk of being fined up to €20 million or 4% of your annual worldwide turnover for not being GDPR compliant. 

  It’s you who has to take action, not Google or other US companies. The court’s decision has immediate effect. While we assume there will be a grace period, companies should act now as finding and implementing alternatives solution can take a while. 

  Can no data be exported outside the EU anymore ?

  Data can still be exported outside the EU if an adequate level of data protection is guaranteed. This is the case for some trading partners of the EU such as New Zealand, Japan, Switzerland, and Canada. They have been certified by the EU as having a comparable level of privacy protection and therefore demonstrate adequacy at a country level.

  Necessary data can still flow to countries like the US too. This is for example the case when someone books a hotel in the US or when sending an email to someone in the US. Backups for disaster recovery and most other reasons don’t qualify as necessary.

  In all other cases you can still send data to countries like the US if you get explicit and informed consent from a user. Meaning the user has been informed about all possible risks of sending the data to the US and who can access the data (for example the US government).

  How this affects Google Analytics and Google Tag Manager users

  If your website is using Google Analytics, the safest bet is to deactivate it immediately. Otherwise, you must ask for consent from everyone who visits your website and inform them that the data will be processed in the United States under less strict privacy laws and all associated risks. If you don’t, you could be liable to privacy law infringements and face being fined for not complying with the GDPR. This also applies to Google Tag Manager as it transfers the IP address to the US which is considered personal data under the GDPR.

  Consent needs to be :

  • Freely given (the user must have a choice to not give consent and be able to opt out at any time) 
  • Informed (you need to disclose who is processing the data, what data is processed, where the data will be stored and how to opt out) 
  • Specific (consent is only valid for the specific informed purpose) 
  • Unambiguous (for example pre-ticked boxes or similar aren’t allowed)

  

  If users don’t give you consent, you are not allowed to track them using Google Analytics or any other US based cloud solution.

  Update August 19, 2020

  A month after this ruling, over 100 complaints have been filed against websites for continuing to send data to the US via Google Analytics or Facebook, by the European privacy campaign group noyb. It’s clear Google and Facebook fall under US surveillance laws such as FISA 702 and the court clearly ruled these companies cannot rely on SCCs to transfer data to the US. Anyone still using Google Analytics is now at risk of facing fines and compensation damages. 

  How this affects Matomo users

  Our cloud servers are based in Germany.

  Matomo On-Premise users choose the location of their data themselves. If the servers are located in the EU nothing changes. If the servers are located outside the EU and the website targets EU users and tracks personal data, then you need to assess whether you are required to ask for tracking consent.

  If the data is stored inside the EU you can use Matomo without asking for any consent and you can continue tracking users even if they reject a consent screen which greatly increases the quality of your data.

  Want to avoid informing users about transferring their data to the US and all associated risks ?

  Try Matomo now for free ! No credit card required.

  Download Matomo