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Esther DiepenhorstBittrates
by on Aug 27, 2015 at 2:49:39 pm

Hello everyone,

I have a question concerning bittrates.

I am working on a job for which I am making a 1080p h264 movie on .mp4 format
This film will be made for two extensions: one is for internet and the other is to be played on screens in stores

I found out that the file plays choppy on computers with some players and correct when uploaded.
I think it is cause of the bittrate that this happens (??)
The screen also shows some blurs here and there when being played on computer

I think this is due to the bittrate so now I am trying to solve this problem.
The target bittrate is now set to VBR, 2 pass and then Target Bitrate MBPS 8, Max bitrate also 8

I don't have a lot experience with rendering, but if I go up wouldn't it get worse? Or is it the other way around.
The best way I know I can test it is by taking a small piece of video to try it out till proper result but I wanted some clearance first so that I am at least sure of what it is I am doing.

Thank you in advance

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Daniel WaldronRe: Bittrates
by on Aug 27, 2015 at 5:01:22 pm

The higher the bit rate, the more processing power it takes for a computer to play it back. When it is too high for a particular computer, you get the results you are seeing. If it is choppy, you should try a lower bit rate. Also, try making your max bit rate a little higher than your target bit rate. This could help making areas of motion or change in your video look better despite a lower overall bit rate. Definitely experiment on short clips to see what your playback computer can handle.

Online video hosts generally re-encode your file to various bit rates and play back which ever one will play smoothly based on the users internet connection.

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Esther DiepenhorstRe: Bittrates
by on Aug 27, 2015 at 5:16:08 pm

Thanks for the reply, I started testing by going through from the tv broadcast preset at 32 and max 40 and working my way down and ended up around 13 with max 25. Now my last question regards the max bit rate, which as you say effects only parts in motion. How much of a difference in numbers between the two is an average use for it, I mean to say is how much is too high of a difference?

Would for example a difference of 20 be alright, can I notice it if it gets too high? With 20 I mean, for now I have calculated it to 13 with max 25, so with the 20 it would be 13 and 33 for instance.

I am guassing if you go too high you won't see much a difference than with lower numbers, but it might still affect filesize(?)

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Daniel WaldronRe: Bittrates
by on Aug 27, 2015 at 9:25:02 pm

Honestly, I don't know the "correct" difference. I generally don't go more than 2-5Mbps higher on the maximum, but don't know if there is an optimum difference or anything.

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Dave LaRondeRe: Bittrates
by on Aug 27, 2015 at 11:28:46 pm

It would also help to know the two delivery specifications you've been given. The more important of the two would be for that in-store playback.

Dave LaRonde
Promotion Producer
KGAN (CBS) & KFXA (Fox) Cedar Rapids, IA

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