MediaConch for Quality Assurance

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MediaConch is a new application developed using the MediaInfo software library, designed with media preservation specifically in mind. The application does many things, from exporting MediaInfo and MediaTrace reports, to fixing mal-formed video files. For more information on MediaConch, see:

MediaConch as a Policy Checker

In a production facility's digital preservation procedures, MediaConch can be used as automated quality control and a policy checker. According to the MediaConch FAQ, “Quality control can be better monitored through MediaConch through algorithmic detection of conformance errors as well as the supplemental institution-based policy conformance checker. Since files are checked in a systematic way, preservationists can know definitively whether or not the file is working or how the file has changed since the last time it was reviewed (whether that is from previous quality analysis or during digitization, ingestion, or migration).”

In effect, the MediaConch software can be used to ensure that the files are encoded to a station's standards, and that they have not been corrupted or otherwise mal-formed.

MediaConch generates reports which can be used as Quality Assurance, a check to make sure that newly created files are encoded as they should be. Particularly when automation is employed to create derivatives, it is not uncommon for a file to be encoded to the wrong specifications. Say, a file intended for editing being transcoded to web specifications, or vice versa. A MediaConch report will help catch those errors at the point of file creation.

MediaConch Reports

MediaConch reports can be generated using a MediaConch policy XML file. The policy files can be created from a template file either through the MediaConch GUI or the command line application. When using the MediaConch GUI, a new MediaConch policy can be created by following these steps: 1: Open the MediaConch GUI (which can be downloaded for free here: 2: Navigate to the “Checker” tab, using the button at the top of the window. 3: Identify a file that can serve as a template for the policy. A policy should be used for files that will be encoded through a specific process with settings that do not change. Choose a file that is created through this process, with these settings, as the template file. 4: Check the template file by clicking on the “Choose Files” button, and then the orange “Check Files” button. The results will appear at the bottom of the screen with the Implementation and Status reports highlighted in green. Click the “Eye” icon under the MediaInfo header. 5: Scroll to the bottom of the MediaInfo report and click on the orange “Create policy from MediaInfo Report” button. 6: The policy will now appear on the Policies page (click the “Policies” tab to view) named after the file name. 7: Check the new policy by running a similarly encoded file against the policy through the Checker. The file will likely fail! MediaConch copies over all of the MediaInfo report fields, some of which are likely to change, even when a file is encoded using the same settings (an example of this is the average bit rate on a file encoded with a variable bit rate). 8: Edit the policy, deleting rules that fail regularly against files that are known to be encoded correctly, until files are passing consistently. 9: Export the policy. Click on the name of the policy at the top of the tree structure, and then click the orange “Export Policy” button.

The policy can then be used to ensure that files are encoded to the specifications the user dictates.

This process can be automated using a .bat file, or Windows “batch file,” which will run a script on the file by dragging and dropping the video file over the .bat file’s “gear” icon, or calling the script via the command line. An example of such a .bat file is shown below:

For %%F in (‘%1’) do ( MediaConch  %1 -p MediaConchPolicy.xml -fh > %%~nF_MediaConch.html)

If the encoding process fails, consult the rules of the policy to determine what elements of the file do not conform to the policy. The rules, based on MediaInfo fields, are listed in the HTML file, shown below:


Further Reading

How to use MediaConch

About Matroska, FFV1, and LPCM

Fixity feature for MediaConch

Recent MediaConch blog posts

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