GH3 GH3 24mbit vs 50mbit, can you really tell a difference?

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thedigitalcurrent

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Try shooting sharp daylight video at small aperture with lots of motion and you see the difference.
 
Cant test these bit rates with stagnate motion. You can learn a thing or two with the testing done on the GH2 "patches". All the encoder's test the bitrates with motion, and a certain type of motion... usually foliage moving in the wind, and preferably something in half shadow.
Usually more motion breaks up in the lesser bitrates...
 
Video compression like this works by predicting motion in a scene or a group of pictures. If you shoot a scene with no motion then both 24mbps and 50mbps will look exactly the same. Where higher bitrates matter is when there is too much motion to predict how the frames should look. So a scene of surfers riding waves in the ocean might start to fall apart at 24mps but the same scene at 50mbps would stay intact with much less quality loss. Shooting a sun bather on the beach would likely look the same at both bitrates since there is no motion.

We tend to shoot as high of a bitrate as we can so the encoder can compensate for complexity changes in the scene. 75% of the time (depending on what you are shooting) 24mbps could be more than enough. It is that other 25% of the time we are glad we shot at 50mbps instead.

The higher the bitrate the less impact it will have on the quality. 50mbps H264 is already pretty darn high to cover most motion situations. You would have to shoot some pretty random extreme detail/motion to have 50mbps break apart. With that said 50mbps isn't going to be 100% perfect and you are still working with predicted frames. 90% of the time that prediction is pretty solid but you could run into a slight quality loss in extreme cases 10% or 5% of the time.

Note noise is a form of random motion to an encoder. This is because every pixel is changing value to random values and the encoder cannot use 8x8, 4x4 or 2x2 blocks of pixles to store frame data. The higher the ISO and the more noise you have the harder it is for the encoder to maintain quality at 24mbps. 50mbps helps a lot here but high noise shooting is better suited for I frame only formats like 200mbps on the GH4.
 
A lot of good advice here. Another thing I'll add is that when shooting a stationary scene at 24mb/s vs 50mb/s, the file size will probably not differ too greatly. Codecs are made to be efficient and if they "think" they are doing a good job of estimating the image with a lower bitrate, they'll use that bitrate. That's the whole point of shooting compressed video, to save file size, otherwise cameras would just all shoot raw. Anyway, the 50mb/s video will be a little bigger (have a higher data rate), but not a whole lot, on a stationary scene. Shoot a lot of detail and motion and the difference in file size will be much greater as the codec increases the amount of image data saved in order to maintain the detail level.
 
blazer003 said:
Anyway, the 50mb/s video will be a little bigger (have a higher data rate), but not a whole lot, on a stationary scene. Shoot a lot of detail and motion and the difference in file size will be much greater as the codec increases the amount of image data saved in order to maintain the detail level.
Click to expand...

GH3 50Mbs MOV is pretty constant codec so the real bitrate is about 50Mbs even in stationary clip.
 
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