Difference between revisions of "MiniDV2AVI/Todo/Extract milliseconds timestampt from DV capture"

Revision as of 21:49, 17 September 2012

I want to extract timecode up to milliseconds from DV capture.

In most known DV format description: http://dvswitch.alioth.debian.org/wiki/DV_format/ written:

Audio/video recording time

byte 0

pack type = 0x53 (audio), 0x63 (DV video) or 0x93 (MPEG-2 video)

byte 1

bits 0-5: frames past second, BCD, or 0x3f = unknown

byte 2

bits 0-6: seconds past minute, BCD

byte 3

bits 0-6: minutes past hour, BCD

byte 4

bits 0-5: hours past start of recording, BCD

But actually, in my experience (and not only my «BYTE magic_FF_6», [1]), this byte 1 is always FF.

60 FF FF 00 FF 61 3F 80 FC FF 62 FF F0 E8 12 63 FF 87 C9 E3 FF

Using «LTC TimeCode frames past second» for guessing «actual milliseconds» is not an option, because LTC is different for each cassette.

Time code (TC)

This is based on LTC but without the sync word. The user bits may be encoded in a binary group pack.

Appears as pack 3 in each subcode block, and also as pack 5 in subcode blocks in the first half of each frame.

byte 0

pack type = 0x13

byte 1

• bits 0-5: frames past second, binary-coded decimal (BCD)
• bit 6: drop-frame timecode flag
• bit 7: colour frame synchronisation flag (irrelevant for DV?)

byte 2

• bits 0-6: seconds past minute, BCD

byte 3

• bits 0-6: minutes past hour, BCD
• bit 7: binary group flag 0

byte 4

• bits 0-5: hours past midnight, BCD
• bits 6-7: binary group flags 1-2

Is there any hack to guess real milliseconds (or frames after second) for timecode?