2 pass recording?

[mpb2000]

What does doing 2 pass recording instead of 1 do to the video quality vs. video file size?

 

[HalloweenOnXmas]

2 pass will improve video AND lower size

 

[mpb2000]

Interesting. So it's a recording time thing. Good to know. Thanks.

 

[mpb2000]

Apparently that is not true. I did some testing and 2 pass definitely adds to file size. For the same original file, I got a 75 MB file for a 1 pass and a 88 MB file for a 2 pass. I can't comment on video quality because I did the test on a short, low quality video. If you converted a whole movie and it only added 20 or 30 MB and showed a noticeable quality improvement, that would be worth it. I'll have to try it out eventually.

 

[Scarpad]

2 Pass is only beneficial if you are using a Variable Bit rate or VBR encoding. The first pass makes notations of the best settings to get a quality encode vs filesize. Then the second pass uses those settings to encode. If you are using a CBR or constant bit rate, there is no need to do two pass becasue it will always use the bitrate you are setting thruout the encode. The beneifits to VBR is that you may get a lower filesize and equal quality. I'm not sure how the 5G handles VBR or if it even can, I always use CBR because I want to maintain the same bitrate thruout and am not to concerned with saving size.

 

[madmaxmedia]

Regarding mpb2000's post- it doesn't necessarily increase file size, but it could. For sure it can improve picture quality/ compression ratio. The first pass gives your a computer an idea of the overall complexity of the movie, so it can then allocate bits more efficiently when it encodes during the 2nd pass.

The iPod can handle VBR pretty well. Check out this thread at Macrumors, at about 1.2 Mbps he was able to get excellent quality with 640 x 360 MPEG4 video. the maximum bitrate for MPEG4 on the iPod is 2.5 Mbps, so there still should be plenty of headroom. The video plays back perfectly on my iPod.

http://forums.macrumors.com/showthread.php?t=156367