File size doubles even though bit-rate is the same

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I added ONE annotation to an MP4 file (original file size = 16Mb, with data rate = 72kbps, total bit rate =125kbps at 25fps) and tried my best to use same settings in camtasia, but my filesize still doubles.  This is what Camtasia says after file is generated.   However, when I view the properties on windows, I get data rate = 155kbps, total bit rate = 218kbps.  Please see below:


From Windows- properties  SAME FILE



This is the original file. Does converting to stereo increase file size that much?  

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jamestweaver

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Posted 2 months ago

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jamestweaver

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I can see that doubling the bit rate should double the file size,  but how can I match up exactly with what my original is?  
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Joe Morgan

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The data rate of the original video is 72 kbps.
The data rate of the Camtasia file is 155 kbps.
The data rate refers to the size of the video file and not the audio.
Camtasia renders with a variable bit rate. You could turn down the quality settings to try to reduce file size.
Or, you can render using bit rate. And adjust the bit rate settings downward.

In most cases, lowering the bit rate/quality is less than ideal. Your re-rendering an MP4. Which is going to harm its quality right off the bat.

Regards, Joe
(Edited)
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jamestweaver

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So what you are saying is that the quality of any mp4 video will diminish every time I modify it with Camtasia then re-generate the mp4 ?   It re-compresses an already previously compressed video? 

If the screen capture is done using  camtasia is this still  a problem?   I mean if I save a Camtasia project, I can edit it as many times as I want,  each time re-generating the video,  without reduction in quality?  


What is the "Best Practice"  for making a 1 hr screen capture,  with intention of modifying it later?   I ask this because I use ZOOM for recording lectures,  and it automatically generates decent quality, small files.  But sometimes I want to modify them.     Do you recommend using Camtasia for the screen capture (for the reasons mentioned)  to obtain decent quality with small files and any modifications I might need?

I hope my questions are clear. 



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gary_bauer

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Your definition of "quality" will be unique to you. That said,I've been playing with bit rate to reduce rendering and upload times. using Bitrate lets you play with the compromise. I've settled on 12K for ZOOM video and 6K if it's PowerPoint static slides.

Good Luck.


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jamestweaver

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It seems that it is best to modify a high quality (but very large)  .mp4,   open it in Camtasia,  modify it, then save as  lower quality, smaller size video ?? (that's a question)
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Joe Morgan

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Here's the deal with zoom.
Zoom is a streaming service that uses very low bit rates to make streaming easy. They do this so people with slow Internet service won't have a problem. I'm sure there's a whole host of other benefits in doing so.
So that leaves you with a lower quality recording to work with.
To the best of my knowledge, there's no way to obtain a higher quality copy from zoom. Bear in mind I don't use the service, so I don't know this to be a fact.

When you edit a video. The original video remains unchanged. In most circles this is known as non-destructive editing.
When you render a new video. That's where degradation can occur. As you're saving it to another file and re-compressing it.
If you want to re-edit the original video again. Reproducing it will yield the same results as before.
When you take an MP4 that has already been re-rendered. Then try to re-rendered that video again. It will be compressed again, leading to further degradation.

Camtasia recordings are AVI's of a very high quality with high bit rates. This is so that when you produce it. And compress it to MP4. You can still achieve high quality results.

However, when you use Camtasia to record a video that is playing. It's been my experience that you can drop a lot of frames. This can/will lead to jittery playback which is less than ideal. You could attempt to record a zoom presentation with Camtasia. You may or may not get acceptable results. You would have to try that for yourself to confirm.

So that kind of put you between a rock and hard place.
You may have to pick your poison here and live with it. I really can't tell you what's best for you.

If you could obtain a very high quality MP4, you could also reproduce it at a lower bit rate with acceptable results.

Hope this clears things up, feel free to inquire further.

Regards, Joe
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jamestweaver

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Thanks for the information, appreciate it