AGK and 29.97

[Nrmf]

how on earth do i set AGK to get 29.97 fps using xvid or divx man am i missing something. everything i get is 23.98. help please.

thank you

[jggimi]

It appears you need a level-set on Film transfers to NTSC video -- a process called Telecining.

Film -- 35mm or 16mm -- runs at 24 frames per second. When this is transferred to 29.97fps video, it is slowed ever so slightly, and every 4 frames, an extra frame is added, using fields from adjacent frames, like so:

http://www.doom9.org/images/Telecine.gif

These extra fields contain no new information, though they consume about 20% of the video content. They exist only to match the requirements of interlaced NTSC televisions for display.

Auto Gordian Knot analyzes your NTSC content, and determines whether the source was originally film, or was shot with a video camera, or was a hybrid of the two, and makes a determination whether or not to conduct an Inverse Telecine process, which would remove those extra, useless fields, and reassemble the proper frames. If so, the framerate will be 23.976 fps, which is very close to the original 24fps of the film.

If your source was an NTSC video camera, which is not film, AutoGK will leave the framerate at 29.97, and deinterlace the frames for progessive display. If you want to control this process yourself, you must make the switch from AutoGK to GK.

For more on Telecining and Inverse Telecining, see www.doom9.org/ivtc-tut.htm. The software it discusses is out-of-date, but the description of fields, frames, and the manual analysis you would need to do when running GK rather than AGK will be helpful.

[unskinnyboy]

@Nrmf, So what jggimi is saying is that AutoGK is doing it right. It is evident that your source material is Film and AutoGK is right in restoring it to 23.976 fps. So now why on earth would you want to do it wrong and waste bitrate encoding duplicate frames?

[laserfan]

@jggimi

:goodpost:
:thanks:

All of Clear, Concise, yet Complete! You get my "Best" award today!!!

[unskinnyboy]

Agree to that. So clear are jggimi's explanations usually, one has to be very very dumb to not get it still. :D

[jggimi]

Thanks for the kind sentiment towards me, but this could certainly be interpreted as unkind: ...now why on earth would you want to do it wrong...Nrmf didn't understand why his NTSC videos weren't 29.97, that's all.

Remember, we were all digital video newbies once, every last one of us.

[unskinnyboy]

Sorry, didn't mean it to be unkind. Was just adopting the same usage as the poster "how/why on earth"...:)

[jggimi]

Thanks for clarifying. ;)

[CWR03]

Something no one has asked Nrmf: what do the 23.976fps encodes look like? Are camera pans really jerky? If not, AutoGK is using the correct framerate.

[laserfan]

...Are camera pans really jerky? If not, AutoGK is using the correct framerate.The only times I have AGK not "get it right" are for certain of my HD Transport Stream captures, which are mostly FILM but for reasons I don't fathom are not "pure film". When therefore detected as Hybrid, and the Decimate argument of the Telecide filter "kicks-in", then I get the panning jerkiness that you describe. So I have to over-ride by using CTRL-F9 and checking "do IVTC when detected as hybrid".

Nrmf, come back and tell us why you think you have a problem.

[unskinnyboy]

Something no one has asked Nrmf: what do the 23.976fps encodes look like? Are camera pans really jerky? If not, AutoGK is using the correct framerate.
_Highly_ unlikely this would happen. Like laserfan said, sometimes the IVTC doesn't get kicked in and the video might be left at 29.971 instead of getting restored to 23.976 (usually with hybrid material), but never the other way around.

[Nrmf]

guys i thank you for all of yall's time, im just new and trying to make sure i can get the best possible picture quailty when taking a dvd rip to a smaller szie file, i like AGK just was thinking that if it said 29.97 then why couldnt i get it to 29.97, other apps i have used will give it 29.97 and as a newbie just thinking that was a better picture, but if its getting rid of excess stuff then i am all for loading AGK up with a ton of jobs and leaving the pc for a week. havent tried to see what they look like on my lcd tv will try that next i guess being new i am a little to anal...i am looking forward to making divx or xvid files and playing them on my home network and portable players. let me do a few and get back with what pic looks like on lcd screem i hope its ok to set fixed width to 960. thanks again all

[unskinnyboy]

Fixed width = 960? You sure your player supports such high resolutions?

[Nrmf]

well wasnt thinking ...play them on pc as well so i assumed a dvd player would handle that too. getting tired of being stupid and slow

[jggimi]

If your sources are 720x480, resizing upwards will not add any detail, though it will consume capacity and bitrate.

Best practice is to resize upward on playback rather than during encoding.

[Nrmf]

thank you

[laserfan]

If your sources are 720x480, resizing upwards will not add any detail, though it will consume capacity and bitrate.

Best practice is to resize upward on playback rather than during encoding.Hi jggimi I was just bragging in a Rebuilder thread about converting a letterboxed DVD to 16:9 anamorphic, to a DL disc so I could retain bitrate while utilizing the full frame size of 720x480 (using Lanczos4Resize).

Is it your opinion that doing these lb-->16:9 conversions is not effective? Intuitively (to me) it makes more sense to up-convert a lb program frame-by-frame at a "leisurely" pace, than to expect hardware in a TV to upsize effectively on-the-fly.

I've read that some folks upsize by 2x or 4x and then Downscale at there TVs with good results. Not sure what to believe... :confused:

[jggimi]

This thread is about creating .avi files -- and so your question on resizing for DVDs is a little off topic.

Secondly, since I don't use Rebuilder, I'm not sure if what you want to do is usual or unusual. Thirdly, I don't exactly know what you're trying to accomplish, probably because I don't use Rebuilder.

If I understand you correctly -- odds are, of course, that I don't understand -- you're doing crops and resizing in order to eliminate letterboxing?

Assuming that my longshot guess is correct, and also with the common understanding that: DVDs have only two DARs -- 4:3 and 16:9. They come in all sorts of ARs, regardless which DAR the authors chose. They have letterboxing or pillarboxing in order to establish proper AR on playback, in combination with the DAR and the AR of the display. If you crop away the letterboxing, and want to retain the content AR ... you will also have to crop away some of the content. If you're doing that, you're basically making a 16:9 pan&scan -- except without the panning.

As to resizing upwards, since there is no detail added, best practice is to avoid it at the compression step. I am not aware of any value added by upsizing before compression. It doesn't mean there isn't any value possible -- someone may come along and show improvements in motion vector analysis or quantization factors -- but I am not aware of any.