nut.txt says: | back_ptr_div16 (v) | back_ptr = back_ptr_div16 * 16 + 15 | back_ptr must point to a position within 16 bytes of a syncpoint | startcode. [...] Does "within 16 bytes" mean before or after the syncpoint startcode? This description also doesn't mention that this value is relative. I think the semantics were intended to be similar to syncpoint_pos_div16 in the index, so probably that description can be copied and adapted: | syncpoint_pos_div16 (v) | offset from beginning of file to up to 15 bytes before the syncpoint | referred to in this index entry. Relative to position of last | syncpoint. Regards, Clemens
On Tue, Jan 23, 2007 at 09:10:43AM +0100, Clemens Ladisch wrote:
nut.txt says: | back_ptr_div16 (v) | back_ptr = back_ptr_div16 * 16 + 15 | back_ptr must point to a position within 16 bytes of a syncpoint | startcode. [...]
Does "within 16 bytes" mean before or after the syncpoint startcode? This description also doesn't mention that this value is relative.
I think the semantics were intended to be similar to syncpoint_pos_div16 in the index, so probably that description can be copied and adapted:
| syncpoint_pos_div16 (v) | offset from beginning of file to up to 15 bytes before the syncpoint | referred to in this index entry. Relative to position of last | syncpoint.
except back_ptr is relative to the current position, not absolute/from beginning of file. and within 16 bytes is supposed to mean that the startcode begins on the pointed-to byte or one of the 15 following bytes. i suppose this could use some clarification in the spec. :) rich
Rich Felker wrote:
On Tue, Jan 23, 2007 at 09:10:43AM +0100, Clemens Ladisch wrote:
nut.txt says: | back_ptr_div16 (v) | back_ptr = back_ptr_div16 * 16 + 15 | back_ptr must point to a position within 16 bytes of a syncpoint | startcode. [...]
Does "within 16 bytes" mean before or after the syncpoint startcode? This description also doesn't mention that this value is relative.
[...] and within 16 bytes is supposed to mean that the startcode begins on the pointed-to byte or one of the 15 following bytes. i suppose this could use some clarification in the spec. :)
Okay. Changes made: - replaced "within 16 bytes of" with "up to 15 bytes before" - mentioned that it's relative - replaced "original syncpoint" with "current syncpoint" (both terms were used for the same syncpoint)
Hi On Fri, Jan 26, 2007 at 10:25:59AM +0100, Clemens Ladisch wrote:
Rich Felker wrote:
On Tue, Jan 23, 2007 at 09:10:43AM +0100, Clemens Ladisch wrote:
nut.txt says: | back_ptr_div16 (v) | back_ptr = back_ptr_div16 * 16 + 15 | back_ptr must point to a position within 16 bytes of a syncpoint | startcode. [...]
Does "within 16 bytes" mean before or after the syncpoint startcode? This description also doesn't mention that this value is relative.
[...] and within 16 bytes is supposed to mean that the startcode begins on the pointed-to byte or one of the 15 following bytes. i suppose this could use some clarification in the spec. :)
Okay. Changes made: - replaced "within 16 bytes of" with "up to 15 bytes before" - mentioned that it's relative - replaced "original syncpoint" with "current syncpoint" (both terms were used for the same syncpoint)
patch applied [...] -- Michael GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB Republics decline into democracies and democracies degenerate into despotisms. -- Aristotle
participants (3)
-
Clemens Ladisch -
Michael Niedermayer -
Rich Felker