Validating MP4 files

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Lara Friedman-Shedlov

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Nov 22, 2021, 5:38:15 PM11/22/21
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Hi all,

This isn't strictly related to BitCurator, but I thought folks in this community might be able to help.  

Does anyone know of a reason why validation of MP4 files generated from VIDEO_TS folders (i.e. video ripped from DVDs) would fail?  We've been using HandBrake to convert these files to MP4 for preservation in our AIPs, but I just realized that when I run the resulting MP4 files through DROID, it does not recognize/validate them.  I tried a couple of other conversion programs, Wondershare Uniconvertor and WinX DV  (well, the free trial versions), and had the same problem with the resulting MP4s.  

Anyone got any insights into this?

/ Lara Friedman-Shedlov

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Lara D. Friedman-Shedlov    (she / they)  (hear my name)
Digital Records Archivist | Archives & Special Collections | www.lib.umn.edu/special
Description and Access Archivist | Kautz Family YMCA Archives | www.lib.umn.edu/ymca
University of Minnesota Libraries | lib.umn.edu | 612.626.7972


Kieran O Leary

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Nov 23, 2021, 4:00:19 AM11/23/21
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Hi Lara, replies below

On Mon 22 Nov 2021 at 22:38, 'Lara Friedman-Shedlov' via BitCurator Users <bitcurat...@googlegroups.com> wrote:
Hi all,

This isn't strictly related to BitCurator, but I thought folks in this community might be able to help.  

Does anyone know of a reason why validation of MP4 files generated from VIDEO_TS folders (i.e. video ripped from DVDs) would fail? 

What validation tool/process are you using exactly? I see DROID used below. 


We've been using HandBrake to convert these files to MP4 for preservation in our AIPs, but I just realized that when I run the resulting MP4 files through DROID, it does not recognize/validate them.

Slightly off topic, but migrating a lossy DVD to a lossier MP4 is less preferable to just preserving the DVD as an iso or something similar? VLC plays back the iso as is. Perhaps the mp4 works better with your system?

Can you post the droid output? It should detect it if it comes from handbrake. 

  I tried a couple of other conversion programs, Wondershare Uniconvertor and WinX DV  (well, the free trial versions), and had the same problem with the resulting MP4s.

This sounds odd, DROID should be able to detect all these. 

Best,

Kieran O’Leary
Digital Preservation Manager 
National Library of Ireland 
  

Anyone got any insights into this?

/ Lara Friedman-Shedlov

--
Lara D. Friedman-Shedlov    (she / they)  (hear my name)
Digital Records Archivist | Archives & Special Collections | www.lib.umn.edu/special
Description and Access Archivist | Kautz Family YMCA Archives | www.lib.umn.edu/ymca
University of Minnesota Libraries | lib.umn.edu | 612.626.7972


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Lara Friedman-Shedlov

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Nov 23, 2021, 12:04:11 PM11/23/21
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Hi Kieran, et al.,

Thanks for your reply. I've been advised that MP4 is preferred for our particular preservation processes.  

The output from running DROID is shown below.  The original folder VIDEO_TS is first.  After that are several attempts to convert the video (which is called "logomaniacs") to MP4 using three different programs, WinX DVD Converter, HandBrake, and VLC.  As you can see below, the ones created by WinX and HandBrake (indicated by the "HB" at the end of the filename) were not identified by DROID.  The VLC one was identified by DROID as a Quicktime file (??) but it won't actually play back in VLC. It seems to be an empty file.


image.png
/ Lara

klpend...@gmail.com

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Nov 23, 2021, 12:04:24 PM11/23/21
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Lara--We also use Handbrake to convert DVD Video to mp4. I hadn't noticed this before either, so I ran DROID and am experiencing the same behavior, with no format results for mp4s from Handbrake while mp4s from our digitization vendor display a PUID, MIME type, and format name.

Viewing the files in a hex editor, the Handbrake file signature doesn't match the mp4 format signature in PRONOM, which is likely why DROID won't recognize it as an mp4 file. I don't have the expertise to know whether there is an issue with file created by Handbrake or if the file is valid and the PRONOM signature needs expansion.

Created by Handbrake, not identified by DROID
00000020667479706D70343200000200          |     ... ftypmp42....
69736F6D69736F32617663316D703431         |    isomiso2avc1mp41 

Created by digitization vendor, identified by DROID
00000018667479706D70343200000000          |     ....ftypmp42....
6D7034326D703431001474616D6F6F76         |     mp42mp41..tamoov

PUID: fmt/199
66747970{0-64}                                                                                    |     {4}ftyp{0-64}
(6D703432|6D703431|69736F6D|69736F32)*6D6F6F76             |     (mp42|mp41|isom|iso2)*moov

I've bolded where the signature matches PRONOM and bold underlined the part from the Handbrake conversion file that doesn't match.

There is a DROID users and developers Google group where someone may be able to provide more information: https://groups.google.com/g/droid-list.


Keith

Lara Friedman-Shedlov

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Nov 23, 2021, 12:13:58 PM11/23/21
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Thank you Keith  -- this is very helpful information. I did a search of the DROID users & developers Google Group you referenced and found this thread, which seems to be relevant. Still not sure whether we should be concerned from a preservation point of view about the fact that what HandBrake generates doesn't have the file signature expected by PRONOM.  Anyone else have thoughts? 

/ Lara



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