DV Date/Time Stamp

[neily]

Hi,

After my previous post about locating dropped frames in captured DV type 2 files, after further investigation I found that one method that works universally is to scan the AVI for the date/time stamps, and if for a given time stamp there were less than 25 frames (PAL user) then within that timestamp there are dropped frames.

I have 2 questions leading on from this. Fisrtly, does anyone know whether the time stamp is recorded in DV files to the nearest second or whether it is more accurate? Every utility I know such as the DV to subtitle programs only report to the nearest second, but I don't know whether this is just for convenience. The paucity of info I found on the innards of the DV file format didn't go beyond D-M-Y and H:M:S.

The second question is whether anyone knows any good links to the detailed file format information? I found about 4 references from which I managed to suss out where the time codes are and how to use them, but I am curious about how the rest of the data is put together.

[bb]

Here's a link with developer information from Microsoft:
http://msdn.microsoft.com/library/en-us/directx9_c/directx/htm/dvdataintheavifileformat.asp

bb

[neily]

Thanks for the reply bb. I was aware of that link. What I was more hoping for was detail at the DIF Sequence / DIF Block level. I think there is a need for a bit of low level examination.

Despite only being into DV for a couple of months, there do seem to be issues regarding captures, especially in regard to handling and reporting dropped frames and, especially with DV type 2 captures, how different capturing utilities construct the files and handle multi-segment captures. It doesn't appear safe to assume that the capture utilities always get it right. As I mentioned previously, different capture utilities handle dropped frames differently. Also, I noticed that using WinDV, when doing multisegment type 2 captures with 2000 frame segments, the audio and video lengths within the segments were different, causing a slight progressive A-V sync drift (at certain other segment lengths there was no problem).