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List:       mythtv-users
Subject:    Re: [mythtv-users] Myth Video Does Not Show File
From:       Jay Foster <jayf0ster () roadrunner ! com>
Date:       2022-01-28 0:04:05
Message-ID: 5f218b5f-c493-b7e7-629c-7bbfebb532e9 () roadrunner ! com
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On 1/27/22 3:32 PM, Jay Foster wrote:
> On 1/27/22 3:15 PM, John Pilkington wrote:
>> On 27/01/2022 22:44, Jay Foster wrote:
>>> On 1/27/22 2:36 PM, Jay Foster wrote:
>>>> On 1/27/22 2:16 PM, John Pilkington wrote:
>>>>> On 27/01/2022 21:19, Jay Foster wrote:
>>>>>> On 1/27/22 12:53 PM, Doug Lytle wrote:
>>>>>>>>>> I have one file that will not show up in Myth Video at all.
>>>>>>> File permissions?
>>>>>>>
>>>>>>> Doug
>>>>>
>>>>>>
>>>>>> Nope.  All files are world read-only (chmod 444).
>>>>>>
>>>>>> Jay
>>>>>
>>>>> IIRC the traditional problem with videos is that the file hash is 
>>>>> not unique.  The remedy is to scan an empty video folder, then 
>>>>> rescan your current one.  I have never known what this does to 
>>>>> metadata.
>>>>>
>>>>> john P
>>>>> _______________________________________________
>>>>>
>>>> I moved the whole series directory to another location not in Myth 
>>>> Videos, Scanned for Changes, and confirmed all of the moved videos 
>>>> were gone.  Then I moved the files back and Scanned for Changes. 
>>>> The same file still does not show up and I lost all of the meta data.
>>>>
>>>> Jay
>>>>
>>>>
>>>> _______________________________________________
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>>>> MythTV Forums: https://forum.mythtv.org
>>>
>>> Looking in the /var/log/mythtv/mythfrontend.log, I see lines like:
>>>
>>> Jan 25 14:18:42 mythbox mythfrontend.real: mythfrontend[31397]: E 
>>> VideoScanner videoscan.cpp:336 (updateDB) Hash 814a23e70734e53a 
>>> already exists in the database, updating record 3147 with new 
>>> filename <new-file-name-here>
>>>
>>> This indicates to me that not only does this file not show up in 
>>> Myth Videos, but some *other* video (record 3147) now points to this 
>>> file, instead of the correct one.  This seems completely buggered to 
>>> me.
>>>
>>> Jay
>>
>> The hash used is quick'n'dirty.  Sorry about the metadata. Perhaps 
>> you could cut one or other of the conflicting files so that they look 
>> different again.  Here's an archived thread.
>>
>> https://lists.archive.carbon60.com/mythtv/users/610359?search_string=hash;#610359 
>>
>
> I tried appending 32 bytes of random data to the end of the file, but 
> still not seen in the video scan.  Despite the above mentioned thread, 
> the hash apparently does not include bytes from the end of the file.
>
> Does anyone know exactly how the hash is computed?  A longer hash 
> (sha256) would reduce the chance of a collision.  How do I find the 
> other video that has been broken (record 3147) and fix it?
>
> Jay

I found and fixed my issue.  By removing the problematic video file, 
scanning for changes, and replacing the file with the modified one and 
scanning for changes, the file finally showed up.  Then I looked at the 
frontend log to find out which other file was being broken.  Turns out 
it was another episode in the same directory.  The reason the hashes 
matched (collided) was because I had inadvertently copied the same 
episode file to both. Fortunately I still had the original recordings in 
the deleted recordings group and was able to fix everything up properly.

Thanks for those who got me there.

Jay

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