Hi ive looked at the vorbis spec and it seems like its trivial to split the 3 header packets if they are simply blindly concatenated the first packet has fixed length the comment header looks like: 1) [vendor_length] = read an unsigned integer of 32 bits 2) [vendor_string] = read a UTF-8 vector as [vendor_length] octets 3) [user_comment_list_length] = read an unsigned integer of 32 bits 4) iterate [user_comment_list_length] times { 5) [length] = read an unsigned integer of 32 bits 6) this iteration's user comment = read a UTF-8 vector as [length] octets } 7) [framing_bit] = read a single bit as boolean 8) if ( [framing_bit] unset or end-of-packet ) then ERROR an they all have a "vorbis" in front of them ... -- Michael GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB In the past you could go to a library and read, borrow or copy any book Today you'd get arrested for mere telling someone where the library is
Michael Niedermayer wrote:
the comment header looks like:
1) [vendor_length] = read an unsigned integer of 32 bits 2) [vendor_string] = read a UTF-8 vector as [vendor_length] octets 3) [user_comment_list_length] = read an unsigned integer of 32 bits 4) iterate [user_comment_list_length] times { 5) [length] = read an unsigned integer of 32 bits 6) this iteration's user comment = read a UTF-8 vector as [length] octets } 7) [framing_bit] = read a single bit as boolean 8) if ( [framing_bit] unset or end-of-packet ) then ERROR
an they all have a "vorbis" in front of them ...
to spare you another read theora is almost the same (but the initial byte are different and you have theora instead of vorbis as string) lu -- Luca Barbato Gentoo/linux Gentoo/PPC http://dev.gentoo.org/~lu_zero
On Tue, Jul 18, 2006 at 11:10:10PM +0200, Michael Niedermayer wrote:
Hi
ive looked at the vorbis spec and it seems like its trivial to split the 3 header packets if they are simply blindly concatenated the first packet has fixed length
the comment header looks like:
1) [vendor_length] = read an unsigned integer of 32 bits 2) [vendor_string] = read a UTF-8 vector as [vendor_length] octets 3) [user_comment_list_length] = read an unsigned integer of 32 bits 4) iterate [user_comment_list_length] times { 5) [length] = read an unsigned integer of 32 bits 6) this iteration's user comment = read a UTF-8 vector as [length] octets } 7) [framing_bit] = read a single bit as boolean 8) if ( [framing_bit] unset or end-of-packet ) then ERROR
an they all have a "vorbis" in front of them ...
excellent, thank you for doing the research to find this. rich
Hi On Tue, Jul 18, 2006 at 11:10:10PM +0200, Michael Niedermayer wrote:
Hi
ive looked at the vorbis spec and it seems like its trivial to split the 3 header packets if they are simply blindly concatenated the first packet has fixed length
the comment header looks like:
1) [vendor_length] = read an unsigned integer of 32 bits 2) [vendor_string] = read a UTF-8 vector as [vendor_length] octets 3) [user_comment_list_length] = read an unsigned integer of 32 bits 4) iterate [user_comment_list_length] times { 5) [length] = read an unsigned integer of 32 bits 6) this iteration's user comment = read a UTF-8 vector as [length] octets } 7) [framing_bit] = read a single bit as boolean 8) if ( [framing_bit] unset or end-of-packet ) then ERROR
an they all have a "vorbis" in front of them ...
how to parse all the vorbis header variants: 1) search for the 1st occurance of 01,'v','o','r','b','i','s' the found match and the following 23 bytes are the 1st header packet 2) search for the 1st occurance of 03,'v','o','r','b','i','s' after here 3) read an unsigned integer of 32 bits and skip that many bytes 4) [user_comment_list_length] = read an unsigned integer of 32 bits 5) iterate [user_comment_list_length] times { 6) read an unsigned integer of 32 bits and skip that many bytes } 7) skip 1 byte 8) the match in 2) and what follows until here is the 2nd header packet 9) search for the 1st occurance of 05,'v','o','r','b','i','s' after here the matching part and what follows is the 3rd header packet if there are no objections then ill propose this on vorbis-dev spelling fixes and other suggestions welcome [...] -- Michael GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB In the past you could go to a library and read, borrow or copy any book Today you'd get arrested for mere telling someone where the library is
Michael Niedermayer wrote:
how to parse all the vorbis header variants:
1) search for the 1st occurance of 01,'v','o','r','b','i','s' the found match and the following 23 bytes are the 1st header packet 2) search for the 1st occurance of 03,'v','o','r','b','i','s' after here 3) read an unsigned integer of 32 bits and skip that many bytes 4) [user_comment_list_length] = read an unsigned integer of 32 bits 5) iterate [user_comment_list_length] times { 6) read an unsigned integer of 32 bits and skip that many bytes } 7) skip 1 byte 8) the match in 2) and what follows until here is the 2nd header packet 9) search for the 1st occurance of 05,'v','o','r','b','i','s' after here the matching part and what follows is the 3rd header packet
if there are no objections then ill propose this on vorbis-dev spelling fixes and other suggestions welcome
[...]
Looks ok. lu -- Luca Barbato Gentoo/linux Gentoo/PPC http://dev.gentoo.org/~lu_zero
On Wed, Jul 19, 2006 at 12:36:27PM +0200, Luca Barbato wrote:
Michael Niedermayer wrote:
how to parse all the vorbis header variants:
1) search for the 1st occurance of 01,'v','o','r','b','i','s' the found match and the following 23 bytes are the 1st header packet 2) search for the 1st occurance of 03,'v','o','r','b','i','s' after here 3) read an unsigned integer of 32 bits and skip that many bytes 4) [user_comment_list_length] = read an unsigned integer of 32 bits 5) iterate [user_comment_list_length] times { 6) read an unsigned integer of 32 bits and skip that many bytes } 7) skip 1 byte 8) the match in 2) and what follows until here is the 2nd header packet 9) search for the 1st occurance of 05,'v','o','r','b','i','s' after here the matching part and what follows is the 3rd header packet
if there are no objections then ill propose this on vorbis-dev spelling fixes and other suggestions welcome
[...]
Looks ok.
Needs to specify endianness for the 'unsigned integer of 32 bits' unless that's already clear from something else.. Otherwise looks good! Rich
On Wed, Jul 19, 2006 at 11:26:47AM -0400, Rich Felker wrote:
On Wed, Jul 19, 2006 at 12:36:27PM +0200, Luca Barbato wrote:
Michael Niedermayer wrote:
how to parse all the vorbis header variants:
1) search for the 1st occurance of 01,'v','o','r','b','i','s' the found match and the following 23 bytes are the 1st header packet 2) search for the 1st occurance of 03,'v','o','r','b','i','s' after here 3) read an unsigned integer of 32 bits and skip that many bytes 4) [user_comment_list_length] = read an unsigned integer of 32 bits 5) iterate [user_comment_list_length] times { 6) read an unsigned integer of 32 bits and skip that many bytes } 7) skip 1 byte 8) the match in 2) and what follows until here is the 2nd header packet 9) search for the 1st occurance of 05,'v','o','r','b','i','s' after here the matching part and what follows is the 3rd header packet
if there are no objections then ill propose this on vorbis-dev spelling fixes and other suggestions welcome
[...]
Looks ok.
Needs to specify endianness for the 'unsigned integer of 32 bits' unless that's already clear from something else.. Otherwise looks good!
entire vorbis spec is spefied like this, all numbers are read in... bah, i don't remember, some endianess.. - ods15
participants (4)
-
Luca Barbato -
Michael Niedermayer -
Oded Shimon -
Rich Felker