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SFmedias
SFmedias
Participant
April 29, 2019
Question

Encoder h.264 changing aspect ratio not changing file size

  • April 29, 2019
  • 1 reply
  • 2392 views

format is H.264 with an mp4 output

Is there something I am missing? I have always heard that you can lower the file size of a video by changing its aspect ratio. When I lower it I can see it obviously makes it lower quality but the "estimated file size" and final file size remains the same. I have also tried changing the width AND height of the frame and the size of the file isnt changing. The only thing I can tell that is changing the file size is the bit rate. Why isn't the aspect ratio effecting it?

Thanks

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1 reply

Justin Taylor-Hyper Brew
Community Expert
Justin Taylor-Hyper BrewCommunity Expert
Community Expert
April 29, 2019

Can you post all your settings used? If your bitrate is the same, AME crams the same amount of data in the output file resulting in the same file size.

SFmedias
SFmediasAuthor
Participant
April 30, 2019

Yes im starting to realize that resolution and apsect ration are linked to bitrate (i guess I don't understand the full reasoning on this). I have it down to 2mbps lol- i am really trying to shrink the video. Couldn't find anything online about explaining why/when resolution and aspect ratio affect the final file size.

Justin Taylor-Hyper Brew
Community Expert
Justin Taylor-Hyper BrewCommunity Expert
Community Expert
April 30, 2019

Just to clarify which kind of aspect ratio you're talking about:

- Video Aspect Ratio: Ratio of dimensions of the video (e.g. 16:9, 4:3, etc)

- Pixel Aspect Ratio:   Aspect ratio of the pixels in the frame (e.g. 1.0, 2.0, etc.)

Most platforms require square pixels, so I wouldn't change that unless they're specifically supported.

Back to size, Bitrate or Mbps is just that Megabits Per Second. How much data is included in each second of video. If you decrease the resolution / pixel aspect ratio, but keep your Mbps the same, it's gonna pack the same amount of data into each second, resulting in the same file size.

What you want to do is decrease the Mbps with your resolution to find a good balance of image quality and file size. This can be a tedious process, so I'd recommend starting with the built-in presets for different delivery platforms (YouTube, Vimeo, etc.) and work from there.

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