GH13 - How do I test data rate improvements? Newbie

K

kipprsnak

New member
Hi,

I was just comparing before and after Tester13 Update and I think I may not know what to exactly look for in terms of changed data rate.

I open both a before file and after file in QT. It looks like I had higher data rates before I used the update. I only modified AVCHD settings, and used the "c" set.

I'm on mac and bringing it in through FCP Log and Transfer into ProRess422HQ.

I'm just wondering if something in my workflow is wrong, or if I shouldn't be bringing it in the way I am...

What kind of numbers should I be seeing in the QT HUD - or is that even the right place?
 
I think you need to look at the clips before they are transcoded. You can just look at their size and divide by clip length.

Chris
 
Thanks for getting back to me about that. Im' trying to figure out what's actually going on. It seems like I am having weird numbers like 114.7 mbits, or 58. Which makes me think that I did something wrong with the hack. No big M.

Thanks for all the help and I'm really looking forward to understanding and using Tester13's work. :)
 
It sounds like you are still looking at the numbers after log & transfer. You have to look at the file sizes on your SD card. In the PRIVATE>AVCHD>BDMV>STREAM folder.

However...the bitrate tells you nothing about video quality. Many folks on this forum are confused about this. You can easily make a high-bitrate video that is lower quality than the default compression. Then you lose both ways...larger files and lower quality.

The only way to assess video quality is to transcode the videos to a high-bandwidth intermediate format, and watch them on a fast-enough machine, and pay close attention.

Individual screen capture of videos also tell you nothing about the quality. An interframe codec like AVCHD only records ~2 i-frames per second. The codec relies on persistence of vision across frames. So you really have to watch the video to assess its quality.

J
 
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