24F cadence... any clues? at DVinfo.net

Dylan Pank · September 23rd, 2005, 07:07 AM

Given that the 24F is supposed to be better tha the Z1's CF24, how will it be encoded to the 60i stream.

Will there be a 2:3:3:2 cedence in addition to 2:3, or will it be output as a true 24 fps file?

I wonder because I got the feeling that the Z1's attempt to do create a 2:3 cadence caused compression artefacts. I got the feeling that jumping between interlaced and un-interlaced frames within a 15 frame GOP pushed the codec a little.

Dylan.

Chris Hurd · September 23rd, 2005, 07:20 AM

Hi Dylan,

I scrolled through the XL H1 menu options last week pretty thoroughly. Indeed there is an option to select 2:3 or 2:3:3:2 for 24F. Keep in mind those were pre-production MT samples though.

Dylan Pank · September 23rd, 2005, 07:35 AM

the 2:3:3:2 cadence is good news, though I'm still concerned. I did get the feeling that having one interlaced frame would sort of reverberate through the compression GOP - it seems to on the Z1.

Steven White · September 23rd, 2005, 08:52 AM

Quote:

I got the feeling that jumping between interlaced and un-interlaced frames within a 15 frame GOP pushed the codec a little.

According to David Newman - who has the best technical understanding of the HDV MPEG-2 GOP compression I know of - the FX1/Z1U is always "flagged" as an interlaced stream - regardless as to whether the data is progressive or something else.

I've never noticed any obvious compression artifacting in CF24 footage above what I would experience with CF30 or 60i.

-Steve

David Newman · September 23rd, 2005, 10:02 AM

Yes, I'm surprize the camera offers 2:3:3:2 as is doesn't need it for HDV. Although it may have marketing value as many do assume incorrectly that it will impact compression quality. However 2:3:3:2 will be handle to support the DV mode, which is helped by this field structure.

September 23rd, 2005, 07:07 AM	#1
Dylan Pank Major Player Join Date: Nov 2004 Location: Portsmouth, UK Posts: 611	24F cadence... any clues? Given that the 24F is supposed to be better tha the Z1's CF24, how will it be encoded to the 60i stream. Will there be a 2:3:3:2 cedence in addition to 2:3, or will it be output as a true 24 fps file? I wonder because I got the feeling that the Z1's attempt to do create a 2:3 cadence caused compression artefacts. I got the feeling that jumping between interlaced and un-interlaced frames within a 15 frame GOP pushed the codec a little. Dylan.

September 23rd, 2005, 07:20 AM	#2
Chris Hurd Obstreperous Rex Join Date: Jan 2001 Location: San Marcos, TX Posts: 27,368 Images: 513	Hi Dylan, I scrolled through the XL H1 menu options last week pretty thoroughly. Indeed there is an option to select 2:3 or 2:3:3:2 for 24F. Keep in mind those were pre-production MT samples though. __________________ CH Search DV Info Net \| 20 years of DVi \| ...Tuesday is Soylent Green Day!

September 23rd, 2005, 10:02 AM	#5
David Newman CTO, CineForm Inc. Join Date: Jul 2003 Location: Cardiff-by-the-Sea, California Posts: 8,095	Yes, I'm surprize the camera offers 2:3:3:2 as is doesn't need it for HDV. Although it may have marketing value as many do assume incorrectly that it will impact compression quality. However 2:3:3:2 will be handle to support the DV mode, which is helped by this field structure. __________________ David Newman -- web: www.gopro.com blog: cineform.blogspot.com -- twitter: twitter.com/David_Newman

September 23rd, 2005, 07:35 AM	#3
Dylan Pank Major Player Join Date: Nov 2004 Location: Portsmouth, UK Posts: 611	the 2:3:3:2 cadence is good news, though I'm still concerned. I did get the feeling that having one interlaced frame would sort of reverberate through the compression GOP - it seems to on the Z1.