[Bug]: Movie preview not generated on remote storages if file > 5MiB

[Digit-al]

⚠️ This issue respects the following points: ⚠️

• This is a bug, not a question or a configuration/webserver/proxy issue.
• This issue is not already reported on Github OR Nextcloud Community Forum (I've searched it).
• Nextcloud Server is up to date. See Maintenance and Release Schedule for supported versions.
• I agree to follow Nextcloud's Code of Conduct.

Bug description

Since this change on 23-Apr (4a924bf), I have no preview generated for Movies uploaded from my phone on my personal space which is a remote storage (NAS). I have no local storage on the nextcloud host.
I switched back to the previous version of Movie.php and the preview are generated again.

Steps to reproduce

1. configure the root space of a user as external storage (SMB on a NAS)
2. use nextcloud client to auto upload picture & movies from the phone to InstanUpload dir
3. there is no preview generated for the movies and the error displayed in the log is :
   {"reqId":"MpJdE6WUzPxfeo8SisaJ","level":3,"time":"2025-06-10T14:17:00+00:00","remoteAddr":"77.131.3.199","user":"user","app":"core","method":"GET","url":"/index.php/core/preview?fileId=8234197&x=256&y=256&a=1&mode=cover&forceIcon=0","message":"Failed to get local file to generate thumbnail for: /user/files/Tmp/Test/PXL_20250610_140337908.mp4","userAgent":"Mozilla/5.0 (Android) Nextcloud-android/3.31.4","version":"31.0.5.1","data":{"app":"core"},"id":"684c15862c051"}

Expected behavior

The preview must be produced as it was with the previous version

Nextcloud Server version

31

Operating system

Debian/Ubuntu

PHP engine version

PHP 8.3

Web server

Apache (supported)

Database engine version

MariaDB

Is this bug present after an update or on a fresh install?

Updated from a MINOR version (ex. 32.0.1 to 32.0.2)

Are you using the Nextcloud Server Encryption module?

None

What user-backends are you using?

• Default user-backend (database)
• LDAP/ Active Directory
• SSO - SAML
• Other

Configuration report

root@nextcloud:~# sudo -u www-data php /var/www/html/occ config:list system
{
    "system": {
        "instanceid": "***REMOVED SENSITIVE VALUE***",
        "passwordsalt": "***REMOVED SENSITIVE VALUE***",
        "secret": "***REMOVED SENSITIVE VALUE***",
        "trusted_domains": [
            "192.168.10.221",
            "pvcld.test.tld"
        ],
        "trusted_proxies": "***REMOVED SENSITIVE VALUE***",
        "overwritehost": "pvcld.test.tld",
        "overwriteprotocol": "https",
        "datadirectory": "***REMOVED SENSITIVE VALUE***",
        "dbtype": "mysql",
        "version": "31.0.5.1",
        "overwrite.cli.url": "http:\/\/192.168.10.221",
        "dbname": "***REMOVED SENSITIVE VALUE***",
        "dbhost": "***REMOVED SENSITIVE VALUE***",
        "dbport": "",
        "dbtableprefix": "oc_",
        "mysql.utf8mb4": true,
        "dbuser": "***REMOVED SENSITIVE VALUE***",
        "dbpassword": "***REMOVED SENSITIVE VALUE***",
        "installed": true,
        "mail_from_address": "***REMOVED SENSITIVE VALUE***",
        "mail_smtpmode": "smtp",
        "mail_sendmailmode": "smtp",
        "mail_domain": "***REMOVED SENSITIVE VALUE***",
        "mail_smtpsecure": "tls",
        "mail_smtpauth": 1,
        "mail_smtpport": "587",
        "mail_smtphost": "***REMOVED SENSITIVE VALUE***",
        "mail_smtpname": "***REMOVED SENSITIVE VALUE***",
        "mail_smtppassword": "***REMOVED SENSITIVE VALUE***",
        "default_phone_region": "FR",
        "memcache.local": "\\OC\\Memcache\\Redis",
        "memcache.distributed": "\\OC\\Memcache\\Redis",
        "filelocking.enabled": true,
        "memcache.locking": "\\OC\\Memcache\\Redis",
        "redis": {
            "host": "***REMOVED SENSITIVE VALUE***",
            "port": 0
        },
        "maintenance": false,
        "maintenance_window_start": 1,
        "ldapProviderFactory": "OCA\\User_LDAP\\LDAPProviderFactory",
        "enable_previews": true,
        "preview_max_x": 1024,
        "preview_max_y": 768,
        "preview_max_scale_factor": 1,
        "preview_ffmpeg_path": "\/usr\/bin\/ffmpeg",
        "enabledPreviewProviders": [
            "OC\\Preview\\IMAGE",
            "OC\\Preview\\Movie",
            "OC\\Preview\\GIF",
            "OC\\Preview\\BMP",
            "OC\\Preview\\XBitmap",
            "OC\\Preview\\MP3",
            "OC\\Preview\\TXT",
            "OC\\Preview\\MarkDown",
            "OC\\Preview\\OpenDocument",
            "OC\\Preview\\PDF",
            "OC\\Preview\\MP4",
            "OC\\Preview\\MOV",
            "OC\\Preview\\MKV",
            "OC\\Preview\\HEIC",
            "OC\\Preview\\JPEG",
            "OC\\Preview\\PNG",
            "OC\\Preview\\AVI"
        ],
        "theme": "",
        "loglevel": 2,
        "memories.db.triggers.fcu": true,
        "memories.exiftool": "\/var\/www\/html\/apps\/memories\/bin-ext\/exiftool-amd64-glibc",
        "memories.vod.path": "\/var\/www\/html\/apps\/memories\/bin-ext\/go-vod-amd64",
        "memories.vod.ffmpeg": "\/usr\/bin\/ffmpeg",
        "memories.vod.ffprobe": "\/usr\/bin\/ffprobe",
        "memories.index.mode": "1",
        "memories.index.path": "\/",
        "memories.index.path.blacklist": "\\\/(Movies|Scans)\\\/",
        "memories.gis_type": 1,
        "files.chunked_upload.max_size": 20971520,
        "app_install_overwrite": [
            "officeonline",
            "maps"
        ]
    }
}

List of activated Apps

root@nextcloud:~# sudo -u www-data php /var/www/html/occ app:list
Enabled:
  - activity: 4.0.0
  - app_api: 5.0.2
  - bruteforcesettings: 4.0.0
  - checksum: 1.2.6
  - cloud_federation_api: 1.14.0
  - contactsinteraction: 1.12.0
  - dav: 1.33.0
  - external: 6.0.2
  - federatedfilesharing: 1.21.0
  - files: 2.3.1
  - files_downloadlimit: 4.0.0
  - files_external: 1.23.0
  - files_pdfviewer: 4.0.0
  - files_reminders: 1.4.0
  - files_sharing: 1.23.1
  - files_trashbin: 1.21.0
  - files_versions: 1.24.0
  - logreader: 4.0.0
  - lookup_server_connector: 1.19.0
  - maps: 1.5.0
  - memories: 7.5.2
  - nextcloud_announcements: 3.0.0
  - notes: 4.12.0
  - notifications: 4.0.0
  - oauth2: 1.19.1
  - oidc_login: 3.2.2
  - photos: 4.0.0-dev.1
  - previewgenerator: 5.8.0
  - profile: 1.0.0
  - provisioning_api: 1.21.0
  - serverinfo: 3.0.0
  - settings: 1.14.0
  - sharebymail: 1.21.0
  - suspicious_login: 9.0.1
  - text: 5.0.0
  - theming: 2.6.1
  - twofactor_backupcodes: 1.20.0
  - twofactor_totp: 13.0.0-dev.0
  - updatenotification: 1.21.0
  - user_ldap: 1.22.0
  - user_status: 1.11.0
  - viewer: 4.0.0
  - webhook_listeners: 1.2.0
  - workflowengine: 2.13.0
Disabled:
  - admin_audit: 1.21.0
  - assistant: 2.4.0 (installed 2.4.0)
  - calendar: 5.2.2 (installed 5.2.2)
  - camerarawpreviews: 0.8.6 (installed 0.8.6)
  - circles: 31.0.0 (installed 25.0.0)
  - comments: 1.21.0 (installed 1.15.0)
  - contacts: 7.0.6 (installed 7.0.6)
  - context_chat: 4.2.0 (installed 4.2.0)
  - dashboard: 7.11.0 (installed 7.7.0)
  - encryption: 2.19.0
  - federation: 1.21.0 (installed 1.15.0)
  - files_downloadactivity: 1.18.1 (installed 1.18.1)
  - firstrunwizard: 4.0.0 (installed 2.14.0)
  - mail: 5.0.2 (installed 5.0.2)
  - officeonline: 3.0.1 (installed 3.0.1)
  - onlyoffice: 9.8.0 (installed 9.8.0)
  - password_policy: 3.0.0 (installed 1.15.0)
  - privacy: 3.0.0 (installed 1.9.0)
  - recommendations: 4.0.0 (installed 1.4.0)
  - related_resources: 2.0.0 (installed 1.0.3)
  - spreed: 21.0.3 (installed 21.0.3)
  - support: 3.0.0 (installed 1.8.0)
  - survey_client: 3.0.0 (installed 1.13.0)
  - systemtags: 1.21.1 (installed 1.15.0)
  - text2image_stablediffusion: 2.0.0 (installed 2.0.0)
  - twofactor_nextcloud_notification: 5.0.0
  - user_oidc: 7.1.0 (installed 7.1.0)
  - weather_status: 1.11.0 (installed 1.5.0)

Nextcloud Signing status

No errors have been found.

Nextcloud Logs

{"reqId":"MpJdE6WUzPxfeo8SisaJ","level":3,"time":"2025-06-10T14:17:00+00:00","remoteAddr":"77.131.3.199","user":"user","app":"core","method":"GET","url":"/index.php/core/preview?fileId=8234197&x=256&y=256&a=1&mode=cover&forceIcon=0","message":"Failed to get local file to generate thumbnail for: /user/files/Tmp/Test/PXL_20250610_140337908.mp4","userAgent":"Mozilla/5.0 (Android) Nextcloud-android/3.31.4","version":"31.0.5.1","data":{"app":"core"},"id":"684c15862c051"}

Additional info

No response

[joshtrichards]

Based on the log entry + code this seems more like a temporary file creation problem in your environment for some reason. You're right that that commit did change behavior, but the log entry you provided only appears if the preview creation is attempted. The log entry indicates things didn't even get as far as creating it though.

We added additional logging for that situation + there was also some refactoring of the TempManager around the same time.

I'm wondering if #51203 introduced something here that impacts your environment.

Any chance you also have any log entries that say something like Can not create a temporary file in directory {dir}. Check it exists and has correct permissions?

[Digit-al]

Hi @joshtrichards ,

You are right, the error message seems unrelated.
However the issue is reproduceable 100%.
What I did:

• 1 - put back the original version of ./lib/private/Preview/Movie.php
• 2 - remove nextcloud.log
• 3 - reboot
• 4 - upload a test file to a test folder (on my root external storage, see picture 1)
• 5 - no preview generated (picture 2)
• 6 - nexcloud.log : 0 byte
• 7 - Modify ./lib/private/Preview/Movie.php:

72c72
<                       //if ($file->getStorage()->isLocal()) {
---
>                       if ($file->getStorage()->isLocal()) {
74,76c74,76
<                       //} else {
<                       //      $sizeAttempts = [5242880];
<                       //}
---
>                       } else {
>                               $sizeAttempts = [5242880];
>                       }

• 8 - reboot
• 9 - preview is generated (picture 3)
• 10 - nexcloud.log : 0 byte

picture 1:

picture 2:

picture 3:

[solracsf]

Well, the (actual) code indeed will prevent any files larger than 5MiB on any remote (files_external, S3...) to be generated.

Code is pretty clear:

if ($file->getStorage()->isLocal()) {
    $sizeAttempts = [5242880, null];
} else {
    $sizeAttempts = [5242880];
}

For local storage: The code attempts to generate a thumbnail first by downloading 5 MB (5242880 bytes) of the file, and if that fails, it tries again with the full file (null size).

For non-local storage (e.g., S3): The code only attempts the 5 MB download and does not fall back to downloading the full file.

[Digit-al]

I agree, but it breaks it for me so I report it as it's maybe not intentional, and it might break it for others looking for a solution.
Maybe you can introduce a config parameter for the user to decide what should be the max size to render preview on remote movies ?
I can keep patching the file if you don't want to revert the change.

[solracsf]

The only solution here is making it opt-in with a config parameter so files on external storages could have no size limits if the admin wants to parse (download) those, no matter the size of those files.

EDIT : See #53496 (comment)