[vorbis] Re: Ogg checksum thingie needed

[Björn Lindström]

Michael Smith <msmith at xiph.org> writes:

> On Thursday 08 January 2004 12:07, Björn Lindström wrote:
>> I need some sort of utility to calculate a checksum of an Ogg file.
>>
>> Two differently encoded Ogg:s should give different checksums, but the
>> same file with different tags should give the same result.
>>
>> (The serial number doesn't work here, obviously. I need something that
>> is changed if a bit of the file is lost.)
>
> Could you explain why you need this?

Yes. I need to keep a database separate from the Ogg:s themselves. I
need a way to find out if the entry in that database does really
correspond a particular Ogg file.

> The ogg framing layer has checksums already embedded in it - so if
> part of the file is corrupted or missing, it's easily detected (see,
> for example, ogginfo - it'll let you know some of this information,
> though not currently all).
>
> If you really need this for some reason - and I'm assuming you want a
> tool for vorbis, not for general-purpose-ogg - then it'd be very
> simple to write one.  Just calculate some sort of hash (perhaps an
> MD5) over the packet data for all packets in the stream except the
> headers.

That seems to be what I need, yes. All that surprises me is that there
is no such tool already. (Built into ogginfo, or something.)


-- 
Björn Lindström <bkhl at elektrubadur.se>
http://bkhl.elektrubadur.se/

--- >8 ----
List archives:  http://www.xiph.org/archives/
Ogg project homepage: http://www.xiph.org/ogg/
To unsubscribe from this list, send a message to 'vorbis-request at xiph.org'
containing only the word 'unsubscribe' in the body.  No subject is needed.
Unsubscribe messages sent to the list will be ignored/filtered.