Audio Encoding and Framerate Conversion Question

[mcpogue]

I have a file that I have converted from 25fps (PAL) to 23.976fps (NTSC), both audio and video. I want to convert these to MPEG so that I can author an NTSC compliant DVD. I know how to convert the video using TMPEGenc, but my question is, in order to have the audio in proper sync with the video, do I need to convert it to 29.97 before I encode it to AC3 or can I leave it at 23.976 and IF I DO need to convert the audio before I encode it, is there a way to keep it from sounding like "Alvin and the Chipmunks"?

Thanks

P.S. tried transcoding audio from 25 fps to 29.97 fps before with BeSweet,
which resulted in audio playing to fast and changing the pitch to Alvin...HELP!!!???

[bugster]

but my question is, in order to have the audio in proper sync with the video, do I need to convert it to 29.97 before I encode it to AC3

No, there is no further need to change the audio. Just encode your video as 23.976fps with 3:2 pulldown enabled and everything will stay the same length and so remain in sync.

[mcpogue]

Is that "3:2 pulldown on playback" on the Video tab, or 3:2 pulldown checkbox in the filters dialog? What's the difference? Does it matter which I choose?

[freebird73717]

If you already have your mpeg video file encoded you can just download and run pulldown.exe
It is relatively fast and there is a gui to make it simpler.

[bugster]

Is that "3:2 pulldown on playback" on the Video tab, or 3:2 pulldown checkbox in the filters dialog? What's the difference? Does it matter which I choose?

Choose the 1st one.

The 1st add encodes at 23.976fps but adds flags to tell the player to repeat certain fields to achieve 29.976fps playback. The 2nd one perfomrs what is sometimes referred to as a 'hard' pulldown. This means it actually generates the extra frames itself and encode s them. This means you have more frames per second of actual data in your final mpeg file, thus less bitrate available for each frame and so a slight reduction in quality. Also the hard pulldown is more likley to end up with jerky playback as I believe it has to generat complete frames whereas the soft pulldown is field based.

[mcpogue]

Encoded the video, but the framerate isn't constant (slows down, speeds up) on playback...like someone pausing and ff a vcr. Is this a field order problem?

[mcpogue]

btw, I used "soft pulldown" during encode...

[bugster]

Encoded the video, but the framerate isn't constant (slows down, speeds up) on playback...like someone pausing and ff a vcr. Is this a field order problem?

Hmm, never come across that with TmpGenc before so 'fraid I don't know what to suggest.

BTW, what format is the source, try posting a gspot screenshot.

[mcpogue]

Source is an Xvid avi (FourCC Code: Xvid). avi is 720 x 480p 23.976fps,
Audio is 96kHz 48kHz 23.976fps.

Encoding audio separately, so using (ES Video Only in TMPGenc)

Latest Xvid Codec is installed.

TMPGenc detected the field order as "B bottom field first" wonder if I need to change this to "A Top Field First"

[mcpogue]

Guess I'm experiencing the phenomenon known as "jerky playback"

Arggghhh!

[bugster]

Xvid's are generally progressive (well, I have never seen or heard about an interlaced one. That doesn't mean they don't exist!) So in TmpGenc you should ignore its field detection and encode as progressive.

Audio is 96kHz 48kHz 23.976fps.

I think you mean 96Kbps
Thats not going to sound too good!

[mcpogue]

Yes, that is what I meant. Well that's the quality of the original source audio believe it or not I know it's not the best quality. Tmpgenc does pick up on the fact that the avi is non-interlaced...and encodes as such. The field order shouldn't matter but its all I can think of, since you did say that a soft pulldown is field based. All I know is that every 5 or 10 secs the video grinds to a complete stop, and then rushes ahead a few frames (not skipping any, just played very rapidly) as if to catch up like someone hit the ff button on a vcr. I know the avi is not interlaced because I did not enable interlacing in the Xvid codec when I encoded the avi (when I tried using interlacing the resulting avi was unplayable).

[mcpogue]

P.S. the playback is the same in Power DVD and WMP....I'm stumped

[bugster]

Try encoding at 23.976fps without any pulldown, video only. Then play the resulting .m2v file on your PC to see if that plays OK. You can do a quick test with just a 5 or 10 minute clip.

If that works use pulldown.exe to add the pulldown flags before you author to DVD.

[mcpogue]

I thought pulldown.exe was for hard pulldown only. Can it be used for soft?

[bugster]

I thought pulldown.exe was for hard pulldown only. Can it be used for soft?

pulldown.exe adds the RFF flags required for soft pulldown. It does not affect the actual video frames or generate any extrat frames that would be required for hard pulldown.

[mcpogue]

So if I want to use tmpgenc to convert my avi to m2v at the original framerate of 23.976 and then use pulldown.exe, what should my settings be so that tmpgenc doesn't try to convert to 29.97? In particular, what should my encode mode be?

[bugster]

Encode mode should be non-interlace.
Frame Rate should be 23.97 fps

[vhelp]

One of the reasons why you (might) be having problems w/ audio sync is
most likely because you *edited* your video (and not your audio) during
the encoding (or frameserving -to- encoding) mode.
.
I think that this is so very overlooked. Because most people are encoding
their sources to an M2V. I could be wrong on this theory, but I know it
to be true (at least for me) because I have done this a few times and
learned/found this out through trial and error - - and then it hit me.
"I was cutting out some video frames, but *not* the audio" Anyways.
Live and learn.

Last night (case anyone forgot what was on tv) I captured "The Grinch.."
(on my noisy antenna) .. it had a two places where an extra Interlace
was thrown in. I had to cut out a few extra frames ( to keep
the IVTC in sync w/ the 3:2 pattern ) when I completed the encode,
(after 40 minutes encode time) it played perfectly on my TV

A little OT here ...

I'm confused though.. cause I thought they didn't use film in those days.
This movie's pattern was PPP D I however, my IVTC method inside
TMPG was spot-on.. even with this odd pattern. And, the movie after
wards, "Scoobee..." was in this same PPP D I format, but w/ more
glitches in the pattern though Anyways.

-vhelp

[snafubaby]

Did you ever figure out the problem with the slow motion video? I made a video, and for some reason, the video is pausing every few seconds, then continuing. It's not a consistant slow motion video. Got any ideas?