Preview of MP4 Videos failing to generate with ffmpeg/avconf if larger than 5MB

[sascha-schieferdecker]

Steps to reproduce

1. Upload MP4 video larger than 5MB, with the moov atom at the end of the file, e.g. from an older android phone. About the moov atom: https://www.adobe.com/devnet/video/articles/mp4_movie_atom.html

Expected behaviour

Video Thumbnail should be generated, works with MPG files.

Actual behaviour

avconf/ffmpeg fail because only the forst 5MB of the video are taken into account, see https://github.com/nextcloud/server/blob/master/lib/private/Preview/Movie.php#L57

If the moov atom is at the beginning of a video, the preview generation works. If the the moov atom is at end of the video, the generation fails. If it is a local file would it be possible to load it completely? Removing the limit in the stream_get_contents call generates the preview just fine. Or maybe would it be possible to streamline the video using something like qt-faststart first?

Server configuration

Operating system: Debian 8

Web server: Apache 2.4

Database: MySQL

PHP version: PHP 7.0.11

Nextcloud version: Nextcloud 10.0 (stable)

Updated from an older Nextcloud/ownCloud or fresh install: No

Where did you install Nextcloud from: Homepage

Please forgive me if I don't post any other configuration details, IMHO they are not relevant to described behaviour.
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[nickvergessen]

Hmm, disabling the switch based on storage sounds a bit weird to me.
I'd say this is fine as is, if the file is too big and does not have "progressive download," "fast start," "use streaming mode," or similar options, I guess that is simply what you end up with?

[sascha-schieferdecker]

Okay, if you define it as expected behaviour, this is what a user ends up with. I am a first time user of nextcloud (never used owncloud). I wondered why there was no preview of most mp4 videos, so I dug into the code. I think I'm not the only user wondering if this behaviour is an error.

In my case I converted the videos to fast start and my problem is solved. But I think most users expect a working preview generation.

Maybe this is more of feature request, depending on how you see it.

[binarydad]

I'm noticing this now, but they're for SMB shares on my local network. Is there a way to force preview generation for videos over 5MB?

[sascha-schieferdecker]

AFAIK no, but you could convert the video with ffmpeg to "fast start", as described here.

Or take a look at qt-faststart, which moves the required information to the beginning of the file.

[binarydad]

Thanks, but how can I tell nextcloud to use these options when generating previews?

[sascha-schieferdecker]

You can't AFAIK. Just run your videos through qt-faststart or ffmpeg in a batch. That's how I solved it.

[binarydad]

Alright, thank you for that. I'll take a look.

Really bizarre... 5MB is nothing. This issue was racking my brain for months, as video previews for larger movies worked fine on local storage, but failed over SMB. At least I know why now...

[kaipee]

Is there a fix scheduled for this? I'm still failing to generate any video (MP4) thumbnails for files stored on 1Gbps SMB share

[liranbx]

I'm also a first time user running into this thing and had to dive into the code to figure it out (too bad this issue was not listed on my google searches).
Was there any progress on this? Is there a branch you're working on?

[binarydad]

So, the way I "solved" this was just bypass the code that is distinguishing between a local and a remote file.

In /var/www/nextcloud/lib/private/Preview/Movie.php, in the getThumbnail() method, is the line $absPath = $this->getLocalFile($file, 5242880); // only use the first 5MB. This is where it's loading a file, but only capping it to 5MB. The getLocalFile() method is inside ProviderV2.php (same directory), which determines whether the file is local or not, eventually setting the $useTempFile boolean flag. If this is true, this is where it loads in an external file, but only 5MB. However, if it's told to load a local file, it will do so, and I've noticed this works fine for SMB files as well.

My fix was to bypass the $useTempFile flag and force getLocalFile() to treat the "external" (SMB shared) file also as local, which allows FFMPEG to read the full file and generate a thumbnail.

I've also tried simply increasing the max file size from 5MB to something much higher, but I feel the overhead of loading an external file the way it does was slower than simply bypassing it and treating it as a local file. I don't know much about PHP but I imagine going directly to the file system to get the file rather than PHP loading it into memory first would be quicker. And I have noticed that thumbnails for larger videos (several GB at least) generate thumbnails a little quicker.

Here's my glamorous fix in ProviderV2.php: 🙃

[kaipee]

@binarydad Just confirming that this 'fix' works great for me too. I have confirmed MP4 large videos are now very quickly generating thumbnails in the Nextcloud Android app, when they completely failed before.

BTW your last sentence should be updated, you've called the file PreviewV2.php instead of ProviderV2.php

[liranbx]

Sorry for the late comment.
From what I understand your solution works because you work with a high speed LAN SMB storage, sadly the same solution won't work for me as I use S3 object storage as a primary storage. It seems as there is no simple solution to creating mp4 previews on a truly remote storage except pulling the entire file without pre-processing the file, because the moov atom placement might be at the end of the file.

My thought is to create some flow application that will pre-process every video file upload to convert it either to webm format or to use qt-faststart to relocate the moov atom.

[binarydad]

Are you using the preview generator CRON job? You can increase the file limit from 5MB to something more reasonable for your case and schedule the preview generation to at least run at night time.

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------ Original Message ------ From: "liranbx" <notifications@github.com> To: "nextcloud/server" <server@noreply.github.com> Cc: "Ryan Peters" <ryan@binarydad.com>; "Mention" <mention@noreply.github.com> Sent: 2/11/2021 1:14:51 PM Subject: Re: [nextcloud/server] Preview of MP4 Videos failing to generate with ffmpeg/avconf if larger than 5MB (#1475)

Sorry for the late comment. From what I understand your solution works because you work with a high speed LAN SMB storage, sadly the same solution won't work for me as I use S3 object storage as a primary storage. It seems as there is no simple solution to creating mp4 previews on a truly remote storage except pulling the entire file without pre-processing the file, because the moov atom placement might be at the end of the file. My thought is to create some flow application that will pre-process every video file upload to convert it either to webm format or to use qt-faststart to relocate the moov atom. — You are receiving this because you were mentioned. Reply to this email directly, view it on GitHub <#1475 (comment)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AANN2XYEV6R5CVGUVAGXH4DS6QNBXANCNFSM4CQI4RQA>.