Is there any Difference between 720p60 or 720p30 data wise?
- Thread starter DJDecay
- Start date
Why add this?
This board is intended to assist people by spreading the knowledge around.
Condescending comments provide what to that?
C'mon.
Al MacLeod
Well-known member
Well, his name is Cranky...
Res ipsa loquitur
Al MacLeod
Well-known member
Barry_Green
Moderator
Usernames don't exempt people from being required to follow rules of simple good manners.
Knock it off, Cranky.
Barry_Green
Moderator
Identical, yes.
Barry_Green
Moderator
There is a flag in the timecode, I think it's in the user bits, that flags active frames versus duplicate frames. OnLocation is smart enough to throw away duplicate frames and only store the active frames, but only in one of its recording modes (Type II avi instead of Type 1, or something... don't remember exactly which one).
Barry_Green
Moderator
The frames are actually duplicated. An intraframe codec means that every frame exists, in its entirety, individually, hence no frame duplication flags.
30pN doesn't travel down the firewire, so OnLocation won't see an HVX/HPX in 30pN mode.
OnLocation has the ability to simulate 30pN mode though, either it's Type 1 or Type 2 AVI that lets OnLocation discard duplicate frames and only store the active frames.
30pN doesn't travel down the firewire, so OnLocation won't see an HVX/HPX in 30pN mode.
OnLocation has the ability to simulate 30pN mode though, either it's Type 1 or Type 2 AVI that lets OnLocation discard duplicate frames and only store the active frames.
So, recording 720/30pN onto a card and then dumping it on a computer will yield a higher-quality video than streaming 720p30 via FireWire?
I am not sure that "an intraframe codec means ... no frame duplication flags." It means no "delta" frames, but why not repeating a whole frame? I googled a bit, did not find anything definitive.
Barry_Green
Moderator
It will result in an identical-quality video stream, but in half the space.
Intraframe means that every frame is compressed individually and stands alone. By using frame-repeat flags, it's no longer intraframe, because inherently the duplicate frame is dependent on the prior frame.
Now I look like an idiot, this always happens when I say "duh". I thought that one could explicitly choose bitrate AND frame rate for DVCPROHD, but instead one chooses frame rate, and bitrate is chosen automatically: 100 Mbit/s for 60fps, 50 Mbit/s for 30 fps native, 40 Mbit/s for 24 fps native. What about 25/50fps? Are these 50/100 Mbit/s or 40/80 Mbit/s? What about overcranking? Is overcranked video recorded with higher bitrate so that when played back with nominal speed (say, 24fps) it had nominal bitrate (say, 40 Mbit/s)?
Also, wikipedia says that DVCPROHD uses 4 parallel codecs, is this true? I mean, is the whole frame divided into four super-blocks and each block is encoded separately?
Also, wikipedia says that DVCPROHD uses 4 parallel codecs, is this true? I mean, is the whole frame divided into four super-blocks and each block is encoded separately?
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Barry_Green
Moderator
The actual bitrate used is dependent on the frame rate, because each and every frame is allocated the exact same amount of bandwidth.
DVCPRO50 uses two codecs ganged together, DVCPRO-HD uses 4. However, DVCPRO50 and DVCPRO-HD also get 4:2:2 color, so I'm not 100% sure how they use those 4 DV codecs in parallel, because DV in and of itself is 4:1:1.
DVCPRO50 uses two codecs ganged together, DVCPRO-HD uses 4. However, DVCPRO50 and DVCPRO-HD also get 4:2:2 color, so I'm not 100% sure how they use those 4 DV codecs in parallel, because DV in and of itself is 4:1:1.
I got this, but is it 100/50 Mbit/s or 80/40 Mbit/s for 50/25 fps, considering that 60 fps is 100 Mbit/s. Ok, I just took a look at the HPX500 info, and it seems that 50/60fps and 25/30fps use the same bitrate, 100 and 50 Mbit/s respectively. Well, duh (may I "duh" myself?), considering that DVCPROHD is a variant of DV, which uses the same bitrate for 50/60 Hz versions.
The last digression in this topic: is it possible to record 24/25/30pN onto tape? I don't mean miniDV tape but large tape.
Barry_Green
Moderator
Tape is always 100mbs. The whole reason the HVX/HPX line have a 720p mode in addition to a 720pn mode, and 1080/24p with 2:3 or 2:3:3:2 pulldown, is because of the way tape (and streaming) work. They have to have that fixed data rate.