Effect of different bitrates

[allynwillard]

I created a project in VideoStudio 2021 Ultimate and rendered it to a MP4 file. I noticed that the file size was about one third the size of similar projects. It turns out that I had used the Custom profiles instead of the MPEG-4 profile and it had a bitrate of 3814 kbps. I rendered it again using the MPEG-4 profile resulting in a bitrate of 13664 kbps and 3 times the file size. Watching both on my computer showed discernible difference in quality. However, I plan to project it on a wall in a auditorium so I may see a difference at that size. My question is: What is the effect of bitrate on the quality of the resultant video?

Thanks for your help.
Allyn Willard

[Ken Berry]

Bitrate is pretty central to the quality of the final video. Within the same format (say, in this case, mp4) a lower bitrate will usually mean a lesser quality when compared to video using a (much) higher bitrate. That's as you have found. If you are worried about space, the downside, if you can call it that, is that the higher the bitrate, the larger the video will be. But that's also as you have found. So when producing a final video, a question you should always ask yourself is do you prefer quality over size. If so, then you use a higher bitrate. If space is an issue, you will need to reduce the bitrate, though hopefully not to a point where quality is bad as to make the video essentially unworkable.

One caveat in all this is the quality of the original video going into a project. If it is already of high quality (e.g. full HD 1920 x 1080 or even 4K 3840 x 2160) then usually you should use an equal bitrate to that used to produce the video in the first place, or something relatively close to it. But if the original video is not particularly high quality to begin with, there is little point of using a much higher bitrate. As the old saying goes, you can't make a silk purse from a sow's ear. You would merely be producing a (much) larger video in terms of size without improving the end quality. In fact, in some cases significantly increasing the bitrate could even conceivably make the final video look worse as it would make any visual defects look sharper or cleaner, and thus more distracting.

The codec used to produce a video can also be important to quality when we are talking about the same format (again, say, mp4). At the moment, for instance, you can use, say, the H.264 codec to produce high quality video at a reasonable size. That video would also be known as AVCHD. But a more recent codec, H.265, can produce video of equal or even better quality, but of smaller size. That can also be called HEVC.

[allynwillard]

Thank-you Ken. That is about what I expected. Size isn't an issue for me. I neglected to mention that my project consist of photos (3000 x 2000 or greater) and video clips (1920 x 1080 at over 16,000 kbps). I am creating a 1920 x1080 MP4 file for viewing. I have created many videos over the years, always 1920 x 1080 at about 13,000 kbps with previous versions of VideoStudio. My current project is the first one done with VideoStudio 2021 and it appears to have defaulted to the Custom profile and that is how I noticed the size difference. Re-rendering it using the MPEG-4 profile resulted in in a file size that I would have expected for the length of the video. Thank-you again for the explanation.

[Ken Berry]

Thanks for the explanation. I should have added that HEVC mp4 is one of the best formats currently available in terms of great quality for size. You can, for instance, set your GoPro Hero 9 or 10 to film using it. The downside is that it requires a fairly powerful computer to handle it smoothly. You haven't got any computer details in your profile so I can't comment on that. But if you come across footage in HEVC and you don't think your computer is up to the job, you can always set VS to enable SmartProxy.