Mp4 atom too large

Server NGINX
1

Hi

I use ngx_http_mp4_module quite heavily, and very occasionally I see
this error for a few files:

mp4 atom too large:723640794

With the number differing… Is the number the size of the atom in bytes?
If so, 723640794 is around 690MB and the mp4 file is only around 150MB

The same file works with the “other” mp4 module

What can we do to find the problem?

Many thanks

2

nginx version: nginx/1.4.1
built by gcc 4.2.1 20070831 patched [FreeBSD]
TLS SNI support enabled
configure arguments: --with-debug --with-http_ssl_module
–with-http_stub_status_module --with-file-aio --with-http_flv_module
–with-http_mp4_module --with-http_geoip_module
–add-module=…/…/…/lua-nginx-module

before u ask :slight_smile:

3

Hi!

mp4 atom too large:723640794

With the number differing… Is the number the size of the atom in bytes?
If so, 723640794 is around 690MB and the mp4 file is only around 150MB

Try increasing mp4_max_buffer_size:
http://nginx.org/en/docs/http/ngx_http_mp4_module.html

Also make sure the MP4 file has the atom at the beginning of the file.

Regards,

Lukas

4

Hi

I already checked there, I’m getting a different error (“mp4 atom too
large” != “mp4 moov atom is too large”)
My error message seems to have been added in this patch
http://nginx.org/download/patch.2012.mp4.txt
In any case, the example given there gives a reasonable example, as
‘12583268’ is around 12MB so increasing it by 2MB would not be an issue
However in my case, the value given is ‘723640794’ which is around 690MB
which is bigger than the actual file!
I believe nginx is reading this information wrong in some way, either by
the mp4 file being invalid or a bug
Either way, I would like help to understand the error

Thanks

5

Hi Richard,

I already checked there, I’m getting a different error (“mp4 atom too
large” != “mp4 moov atom is too large”)
My error message seems to have been added in this patch
http://nginx.org/download/patch.2012.mp4.txt
In any case, the example given there gives a reasonable example, as
‘12583268’ is around 12MB so increasing it by 2MB would not be an issue
However in my case, the value given is ‘723640794’ which is around 690MB
which is bigger than the actual file!

I see. Is this limited to certain files, and can you reliable reproduce
this issue on those files? Can you rerun those files through a mp4
demuxer/muxer, so that the atom is rebuild? I believe there is a good
possibility that the atom in the mp4 files is bogus, either due to
a muxer bug or a truncated file.

You can do this with mp4box [1]:
MP4Box -inter 500 -out output.mp4 input.mp4

I looks like you are running on FreeBSD, can you clarify the release
and what platform you are running (x64, i586, or else?).

Also, reproducing this with fully enabled debugging will probably help
the developers (if this is really a bug in the mp4 module):

http://nginx.org/en/docs/debugging_log.html

The same file works with the “other” mp4 module

That doesn’t necessarly mean there is a bug in the nginx module, the
“other” module could just ignore bogus atom for example.

[1] MP4Box · gpac/gpac Wiki · GitHub

Regards,

Lukas

6

Hello!

On Sat, Jun 29, 2013 at 09:50:53AM +0100, Richard K. wrote:

690MB which is bigger than the actual file!
I believe nginx is reading this information wrong in some way,
either by the mp4 file being invalid or a bug
Either way, I would like help to understand the error

The message in question means that the file is broken - the size
of a mp4 atom recorded in the file is greater than the file size.

If there are reasons to assume the file is ok, debug log should
give you enough information to compare what nginx thinks with what
is in the file.

–
Maxim D.
http://nginx.org/en/donation.html