fps 29.970 vs 29.974

[4evrplan]

I noticed MediaInfo says one of my clips is 29.970 fps. However, when I run the same video through AutoGK, the script it generates uses 29.974 fps. Is one of these a bug?

[johnmeyer]

29.97 is the standard NTSC frame rate.

23.976 is the standard film rate for film transferred to DVD.

29.974 is not a standard video rate. However, it is possible to set the playback rate of a video file to any number you want, so I wouldn't call such a result a bug. However, it is most definitely not standard.

[Zarxrax]

He was saying the same video has different framerates reported depending on what software checks it
I would lean towards mediainfo being more accurate.
It could be that the video is variable framerate of some sort?

[manono]

Since AutoGK doesn't use VFR, it would be the same as the source. AutoGK is only capable of (for NTSC) 29.97fps or (if IVTC'd) 23.976. Whatever is reading the framerate is doing it incorrectly.
...when I run the same video through AutoGK, the script it generates uses 29.974 fps.
How do you know that? What are you using to determine the framerate? Try opening the script in VDub(Mod) and going File->File Information to check the framerate.

[4evrplan]

How do you know that? What are you using to determine the framerate?

When you run a job in AGK, it creates a temp folder named agk_tmp. In that folder is an AVS script named ...movie.avs. I can open it up in a text editor to see what AGK wrote to the script, and the first line ismovie = DirectShowSource("...",29.974).KillAudio()

When I open the same clip in in MediaInfo, it reports that it's 29.97 FPS.

[manono]

The audio is in synch with the video afterwards, isn't it? Then I wouldn't worry about it. As far as I know, AutoGK can't stretch audio. I'm surprised AutoGK is using DirectShowSource. This isn't from a DVD then? Maybe from some sort of an AVI? When you say you open the same clip in MediaInfo, is that the source video, or the AVI after AutoGK gets finished? What do other apps say about the final framerate (GSpot, VDub(Mod), etc.)?

[4evrplan]

No, not a DVD. The source is a flash video I'm reencoding to a format my standalone understands. MI says the source is 29.970 FPS. I used AVS/VirtualDubMod to save it to an intermediate format that AGK understands, HuffYUV using the original YV12 colorspace and PCM audio. I used 29.974 FPS in my script when I did this encode, but even so, MI reports the result is at 29.970 FPS just like the original. However, VDM reports the intermediate to be at 29.974 FPS, just like I specified in my script. When I do the final encode with AGK, MI reports 29.970 FPS for the result, and VDM reports 29.974 (also matches the script AGK generated). Perceptually, everything does seem to be in sync. It might make a difference for a longer video though. After writing this all out, I'm thinking the bug must be in MediaInfo, since VDM and AVS seem to agree.

[4evrplan]

GSpot shows:
original 30.026 FPS
intermediate 29.974
final 29.974

EDIT: I just opened a different (but similar) clip via AVS/VDM at the framerate reported by GSpot, and it was clearly too fast. The video was ahead of the audio by the end of it.