On 24/02/10 03:23, Michael Riepe wrote:
> As part of my work on dvbcut2, I've developed a new algorithm for file
> format detection.
Do you plan to allow edit/trim of all sorts of media files ?

> The basic idea is that the beginning of a file - say,
> a few megabytes at most - is searched for magic byte sequences. But only
> once. If you scan the file again and again for every file format you're
> supporting, you'll waste a lot of time - in particular when the list
> includes not only MPEG PS/TS (as in dvbcut) but also AVI, Matroska, Ogg,
> M2TS (a variant of TS used on the Blu-ray disc) and possibly others.
> Besides that, the probing order may affect the result.
Are the ffmpeg library methods no good to you ?
I would have imagined that they might already do what you are intending 
(without ever having used them myself) ?

> Anyway, I've packed the necessary bits and bytes into the attachment and
> I would like to ask you to test them on any file you can get your hands
> on. I'm particularly interested in all misdetected and undetected files.
> I want the detection to work as flawlessly as possible. Oh, and if you
> think an important format is missing, don't hesitate to tell me.
I'm guessing you wouldn't expect to be able to handle encrypted wma/f/asf ?

> Afterwards, you can run ./container<filenames>  (for container files) or
> ./media<filenames>  (for all others).
Might be nicer for the detection to tell us ?

===== nvidia demo videos, archived elsewhere:
note that other files in the group that were downloaded at the same time 
all detect normally (prob 83 .. 100% raw MPEG-1/2 video

http://findthatfile.com/fileinfo.php?i=5985342&t=hZIP&f=Gothic_Chapel.zip

cont gothic_chapel.mpg:
- I don't know what kind of file this is

media gothic_chapel.mpg:
- seems to be raw MPEG-1/2 video                       (probability  95.2%)

   libavutil     50. 3. 0 / 50. 3. 0
   libavcodec    52.37. 1 / 52.37. 1
   libavformat   52.39. 2 / 52.39. 2
   libavdevice   52. 2. 0 / 52. 2. 0
   libavfilter    1. 4. 1 /  1. 4. 1
   libswscale     0. 7. 1 /  0. 7. 1
   libpostproc   51. 2. 0 / 51. 2. 0
[mpegvideo @ 0x273a5e0]max_analyze_duration reached
Input #0, mpegvideo, from '/home/media/3d-demo/nvidia/gothic_chapel.mpg':
   Duration: 00:01:35.22, bitrate: 1152 kb/s
     Stream #0.0: Video: mpeg1video, yuv420p, 352x240 [PAR 200:219 DAR 
880:657], 1152 kb/s, 30 tbr, 1200k tbn, 30 tbc

=====
Anyway, I have quite a few with outputs eg:
/home/media/wmap_nasa_030640.avi:
- seems to be an ASF file                              (probability 100.0%)
Seems stream 1 codec frame rate differs from container frame rate: 
1000.00 (1000/1) -> 15.00 (15/1)
Input #0, asf, from 
'/home/media/client_clips/transport_hotel.player/tport/tport/movies/wmap_nasa_030640.avi':
   Duration: 00:00:45.51, start: 3.000000, bitrate: 414 kb/s
     Stream #0.0: Audio: wmav2, 8000 Hz, 1 channels, s16, 5 kb/s
     Stream #0.1: Video: wmv1, yuv420p, 640x480, 15 tbr, 1k tbn, 1k tbc
   Metadata
     title           :

I guess that the extension was wrong.

===== all these are A+V mpeg2 files (without looking further)!
/home/media/CT 15th April 2008 Tuesday.avi:
- I don't know what kind of file this is

/home/media/Sports_bar_fosters.avi:
- seems to be 44100 Hz MPEG-1 Layer I audio            (probability  60.7%)

/home/media/rendered/elephants_dream/Elephants_Dream_HD.avi:
- I don't know what kind of file this is

/home/media/rendered/blender_movie.learning_to_fly_BIG.avi:
- seems to be 44100 Hz MPEG-1 Layer I audio            (probability  62.8%)

/home/media/trailers/games/quake_iv.eoc.bad_q4singleplayer.avi:
- seems to be raw FLAC audio                           (probability  61.2%)
AVI file format detected.
[aviheader] Video stream found, -vid 0
[aviheader] Audio stream found, -aid 1
VIDEO:  [DIV3]  400x300  24bpp  20.000 fps  888.6 kbps (108.5 kbyte/s)
Opening video filter: [pp=fd]
==========================================================================
Opening video decoder: [ffmpeg] FFmpeg's libavcodec codec family
Selected video codec: [ffdivx] vfm: ffmpeg (FFmpeg DivX ;-) (MSMPEG-4 v3))
==========================================================================
==========================================================================
Opening audio decoder: [mp3lib] MPEG layer-2, layer-3
AUDIO: 22050 Hz, 2 ch, s16le, 40.0 kbit/5.67% (ratio: 5000->88200)
Selected audio codec: [mp3] afm: mp3lib (mp3lib MPEG layer-2, layer-3)
==========================================================================
AO: [pulse] 22050Hz 2ch s16le (2 bytes per sample)

=====
Anyway, it is a bit time consuming to go through lists of thousands of 
files, trying to pick out the troubling media files.
It would speed up the process for me to put each result on a single 
line, with the detected type first. Then I could just sort the file, 
ending up with the list of troubled files in groups, just an idea.
(maybe you have a better idea - so that manual parsing is not needed).

Anyway, some of the troubling ones were made with dvbcut1 (captured from 
dvb transport, and cut up with dvbcut - I have used inbuilt mux only 
when ffmpeg mux crashes dvbcut).

Not sure how you would like media files, eg grab first 1-2 MB and upload 
it to your server ?

Cheers, DaveT.

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