Wildly different rendering times (to Flash) for two similar videos?
 

I have two videos of university courses: Video A is about 3h15m, video B is about 3h. Both are NTSC DV videos and match perfectly as far as resolution, bitrate, etc. go (I shot them both myself using the same camera). My computer's about three years old so I expected long rendering times, but I was going to leave it running unattended so that wasn't much of an issue.

Using Adobe's Flash Video Encoder (CS3), video A took about 22 hours to encode at 400bps and gave perfectly acceptable results; using the exact same profile, video B was set to take over 40 HOURS before I killed it halfway through!

And here's the kicker: not only is video B shorter (and should logically take less time than video A), but the quality of the flash encode was horrendous! Lots of artefacts and blurred lines, to the point where the writing on the blackboard was illegible. And yet it would take twice the time to render.

What gives? I did 30-second tests of both videos to make sure it wasn't a fluke, and the results were consistent: at the same 400 bps setting, video B took much longer and yielded worse image quality than video A

I can only imagine the problem lies with content. Both videos are of an instructor at a blackboard, with similar camera movements and zooms. So what exactly makes it so one video will take twice as long to render as the other? The lighting changes slightly from one room to the next, but it's sufficient in both cases.

I feel like someone's playing a lousy prank on me. None of it makes any sense, and I hope someone will have an answer, if not a fix.


J.

Just a stab here.....

But did you have the export set for Entire sequence, or Work area bar??
Also, another stab....Perhaps a reboot, and try the shorter clip again...

I'm using the standalone Adobe Flash Encoder, not Premiere. And as I said, I did 30-second tests to confirm my findings, and tried different computers. The results remain the same. The software wouldn't consistently "malfunction" on only one of the two clips.

Look carefully at the project and sequence settings for the two projects. It seems likely that the two are not the same.

I'm using the standalone Adobe Flash Encoder, not Premiere. There are no timeline or project settings. In the flash encoder I use the exact same preset for both videos (400kbps).

Both videos were initially rendered in Vegas using the exact same preset. When I encountered the problem, I looked closely at the properties of both videos to make sure I had made no mistake: same bitrate, same codec, same resolution.

I let the flash encoding process run overnight for the second video. The estimated time left was 36 hours; when I checked 12 hours later, it was still at 36 hours left. The preview windows shows that it's progressing, but the longer it goes the slower it gets.

I then did a flash encode using Total Video Recorder, which progressed normally and was set to take about 3 hours (not >35!). The quality, however, was bad, which I guess is due to the software doing quick and dirty transcoding. I'm beginning to suspect a bug from Adobe CS3 (it would not be the first time - there's a reason I use Vegas whenever I can) compounded by a tiny glitch between the two videos which I haven't been able to detect.

I'm doing more tests and will report on the findings. I am not, however, impressed, as this is for a paying client. If my workflow was to blame I'd get similar problems with both videos. There's software that's not doing the job it's supposed to do, and past experiences make me suspect Adobe.


J.