encoding 30/60 fps with vegas 11, file sizes question

J

joker454

Well-known member
Hey guys, I have a question on something that is puzzling me a bit. I'm recording source footage at 1920x1080 60p 28mbps, and now I'm trying to determine what to encode the final files at. I'm trying with both h264 and wmv. Wmv gives me both 30fps and 60fps options, whereas h264 only gives 30fps. So I setup similar specs on all codecs (1920x1080, ~8mbps average, ~20mbps peak) and encoded three test files at similar resolution and bitrate all with Vegas 11 pro, with these results:

h264 30fps encode: 346mb file size
wmv 30fps encode: 354mb file size
wmv 60fps encode: 355mb file size

What's confusing me is the wmv 60fps encode. How is it possible that the file size of that one is almost identical to the 30fps encodes? Shouldn't it be far larger? I watch all the videos and clearly two are at 30fps and one at 60fps, it's easily visible. I just don't understand how the file size isn't much bigger on the 60fps encode!
 
Would have to see the complete settings.

Depending on a few things, a matching bitrate at a lower frame rate can give you the same file size as that of a higher frame rate, but with higher-quality frames.
 
What is the playback target you are encoding for ?

i.e. YouTube, Vimeo, Blu-ray, digital projection, etc...
 
Ah I see, well the wmv encoder has a few choices. One is just bitrate average, for that one I would have assumed that both 30fps and 60fps versions would be the same filesize since the encoder is just targeting an avarage bitrate, and hence file sizes would end up similar with the 60fps version having less data per frame to meet the average. I used the other setting on both 30fps and 60 fps encodes, the "Bit rate VBR (Peak)" option. Settings for that are:

Image size: keep original size (1920x1080)
Pixel aspec: 1.0 (square)
Seconds per keyframe: 5
Average bit rate, 8m
Peak bit rate, 20m
Peak buffer size, 20 sec

For that one I assumed that the "Peak bit rate" setting would let the 60fps consume more bitrate as needed compared to the 30fps encode. My logic was that it mean ok, i want 8mbps on average but you are free to use up to 20mbps at times if you really need it. Maybe my thinking is wrong there? There is also a "Quality vbr" encode option where you just set a qualtiy percentage, I'll try that as well on both 30fps and 60fps encodes and see if there is a file size difference there. Maybe I'm just misunderstanding the "Peak vbe bitrate" encode options on Vegas.
 
joker454 said:
It's for an internet members website.
Click to expand...

...So are you using custom Flash players to stream your video from the website, or are you streaming via QuickTime, or are you using dedicated streaming video servers, or do you expect your members to download the video and play the video on their local hard-drive once it's downloaded.

I've been using custom Flash players to stream FLV encoded videos from our own media servers for more than 5 years now, and in the last year we've started to use YouTube as well.
 
TheDingo said:
...So are you using custom Flash players to stream your video from the website, or are you streaming via QuickTime, or are you using dedicated streaming video servers, or do you expect your members to download the video and play the video on their local hard-drive once it's downloaded.

I've been using custom Flash players to stream FLV encoded videos from our own media servers for more than 5 years now, and in the last year we've started to use YouTube as well.
Click to expand...

No streaming, they are meant to be downloaded and kept by the users. I'm trying to step up the quality for these two new sites I'm making, hence why I'm going full hd with high bitrate, I think most peoples computers are now up to the task of playing back such videos. Mostly trying to decide between 30/60fps now. 60fps fits the themes of the sites but I was just curious why the file sizes weren't much larger. I'm doing some test encodes now with the "qualtiy vbr" setting at both 30 and 60 fps, I'll see if that brings out a file size difference.
 
For maximum quality and moderate file size I would use the Sony AVC Mpeg-4 format, and begin with either the YouTube or Vimeo encoding guidelines as your starting point. ( see links below )

YouTube Advanced Encoding Specifications

Vimeo Compression Guildelines ( click on Vegas 9 or 10 icon to watch encoding tutorial )

...You will have to create your own custom Vegas encoding templates for these formats, which is very easy to do. Just follow the recommendations listed in these guidelines. ( YouTube might be the better one to use )
 
Thanks, although I'll probably stick with wmv. Google analytics shows about ~91% of my customers using windows machines, so using wmv means no "i cant play the video" support emails to deal with.
I just did another test, this time encoded the same test clip with the "Quality VBR" setting, and I set quality at 86%. In that case the resultant files were:
30fps file: 341mb
60fps file: 516mb

That's more what I would expect! I guess the "peak vbr" encoder doesn't use the peak value at all which is odd, I guess I'll just stick with the "quality vbr" encoder setting.
 
joker454 said:
Ah I see, well the wmv encoder has a few choices. One is just bitrate average, for that one I would have assumed that both 30fps and 60fps versions would be the same filesize since the encoder is just targeting an avarage bitrate, and hence file sizes would end up similar with the 60fps version having less data per frame to meet the average. I used the other setting on both 30fps and 60 fps encodes, the "Bit rate VBR (Peak)" option. Settings for that are:

Image size: keep original size (1920x1080)
Pixel aspec: 1.0 (square)
Seconds per keyframe: 5
Average bit rate, 8m
Peak bit rate, 20m
Peak buffer size, 20 sec

For that one I assumed that the "Peak bit rate" setting would let the 60fps consume more bitrate as needed compared to the 30fps encode. My logic was that it mean ok, i want 8mbps on average but you are free to use up to 20mbps at times if you really need it. Maybe my thinking is wrong there? There is also a "Quality vbr" encode option where you just set a qualtiy percentage, I'll try that as well on both 30fps and 60fps encodes and see if there is a file size difference there. Maybe I'm just misunderstanding the "Peak vbe bitrate" encode options on Vegas.
Click to expand...

Can you show screenshots of the render settings of each version?
 
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