[Matroska-devel] File with no SeekHead

Dan Hinsley danhi at cox.net
Fri Sep 14 23:29:43 CEST 2012


Attached is the output, with detail removed.  At the end of the file you'll
see a SeekHead with a Seek pointing to the Tags Element.  The Seek Position
is listed as 23343847.  When I look at the file with HexEdit, that is
exactly the value in the Seek Position Element.  In other words it's
relative to the start of the file, not the beginning of the segment data
(0x20) or the first Level 1 Element (0x51).

Dan

+ EBML head at 0
|+ Doc type: matroska at 5
|+ Doc type version: 2 at 16
|+ Doc type read version: 2 at 20
+ Segment, size 23380900 at 24
|+ EbmlVoid (size: 47) at 32
|+ Segment information at 81
| + Duration: 87.336s (00:01:27.336) at 87
| + Muxing application: libebml2 v0.10.1 + libmatroska2 v0.10.1 at 94
| + Writing application: mkclean 0.5.5 r from libebml v1.0.0 + libmatroska
v1.0.0 + mkvmerge v4.0.0 ('The Stars were mine') built on Jun  6 2010
16:18:42 at 136
| + Date: Sat Aug 21 16:31:55 2010 UTC at 268
| + Segment UID: 0x84 0xfa 0x5b 0x60 0x97 0x2a 0x16 0x5b 0x85 0x27 0x66 0xe7
0xe5 0xb0 0xa2 0x83 at 279
|+ Segment tracks at 298
| + A track at 304
|  + Track number: 1 (track ID for mkvmerge & mkvextract: 0) at 306
|  + Track type: video at 309
|  + Codec ID: V_MS/VFW/FOURCC at 312
|  + Track UID: 2422994868 at 329
|  + Default flag: 0 at 336
|  + Lacing flag: 0 at 339
|  + MinCache: 1 at 342
|  + CodecPrivate, length 40 (FourCC: MP42, 0x3234504d) at 346
|  + Default duration: 41.667ms (24.000 frames/fields per second for a video
track) at 389
|  + Language: und at 397
|  + Video track at 404
|   + Pixel width: 854 at 406
|   + Pixel height: 480 at 410
|+ Tags at 23343928
| + Tag at 23343934
|  + Simple at 23343938
|+ Attachments at 23344965
| + Attached at 23344972
|  + File name: cover.jpg at 23344977
|  + Mime type: image/jpeg at 23344989
|  + File data, size: 34832 at 23345002
|+ Chapters at 23379839
| + EditionEntry at 23379845
|+ Seek head at 23380794
| + Seek entry at 23380800
|  + Seek ID: 0x12 0x54 0xc3 0x67 (KaxTags) at 23380803
|  + Seek position: 23343847 at 23380810
| + Seek entry at 23380821
|  + Seek ID: 0x19 0x41 0xa4 0x69 (KaxAttachments) at 23380824
|  + Seek position: 23344884 at 23380831
| + Seek entry at 23380842
|  + Seek ID: 0x10 0x43 0xa7 0x70 (KaxChapters) at 23380845
|  + Seek position: 23379758 at 23380852

-----Original Message-----
From: matroska-devel-bounces at lists.matroska.org
[mailto:matroska-devel-bounces at lists.matroska.org] On Behalf Of Moritz
Bunkus
Sent: Friday, September 14, 2012 2:15 PM
To: Discussion about the current and future development of Matroska
Subject: Re: [Matroska-devel] File with no SeekHead

Hey,

mkvinfo is a developer tool that doesn't interpret the values (too
much). In this case this means that it simply prints the raw values of
the elements beneath Cues. The interpretation ( = adding them to the
segment data start position in order to retrieve the absolute file
position) is up to the user.

> I understand that this is probably non-standard, but just trying to cover
> all possibilities.  I created a file with no SeekHead.  So from reading
the
> spec, what I should do is create one that is referenced off the first
Level
> 1 Element (in my case a Segment Info Element).

I don't really get what you mean by "...create one that is referenced
off the first level 1 element". Can you please paste mkvinfo's output
(with -v -v, possibly remove all cluster-related information, upload
it somewhere)?

Kind regards,
mosu
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