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I love Sony Vegas, but………
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Ok, that sounds fine. I’m just trying to reconcile that with what Sony has posted in their help files –which implies that video of similar quality (and similar bitrates), when in 24p form, takes up less space than the same video in 29.97 form.
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Thanks Liam.
When you choose constant bitrate, it greys out the min, max and average settings. So unless the rendered factors in those numbers *before* they’re greyed out, I wouldn’t suspect they’d make a difference. Would be worth noting if they did.
I definitely respect your experience and the experience from all the other users on here. And if the end result is simply that a 24p file of similar bitrate and quality is no different in size than a 29.97 file, I’m fine with that. My goal has simply been to reconcile my experience with Sony’s own help files, which seem to clearly state the opposite. Perhaps if Sony’s help was more helpful, this all could have been cleared up in the first place. 😉
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I would not take what Sony placed in their help files to imply what you say it does. You added in some “words” (Same Quality / Bit Rates) to match up with what you thought should be the case.
I do agree… that more information in the help file about the trade-offs involved would have cleared it up. But… in the end.. Sony did not make up this 24p thing and how that factors into MPEG encoding.
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Fair enough…
But Sony writes: 24p video uses less space on a DVD… That’s pretty straightforward, right?? It doesn’t say “24p video uses less space on a DVD — if you use a lower bitrate”. If it said that, then this whole mess could’ve been cleared up in the first place!!
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Yes… you are correct… we have heard you (many times). All I have been attempting to do is to bring to your attention what the state of things really is… despite the lack of some specific words from a help document. Perhaps you should go along to the Sony site and submit a product suggestion to them.
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I’m sorry you had to hear me *many times*… The reason I had to repeat myself *many times* was that despite the many posts, I didn’t receive an answer that reconciled my personal rendering experience with what Sony wrote. If it was simply an error in Sony’s help files, that was fine. Or if it was something I was doing wrong in my renders, that’s fine too. I was getting more than one answer from more than one source, which only complicated things and muddied the issue. I’m not a dense guy — but in this situation, 2 and 2 hasn’t seemed to add up to 4.
By the way — did anything come out of your test renders?
Best wishes…
Marc
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video of similar quality (and similar bitrates), when in 24p form, takes up less space than the same video in 29.97 form
The sentence over is actually not making sense, and I think this is where the confusion starts for you. Let’s look at it bit by bit (the no-sense part).
Video of similar quality and similar bitrate…
If you have two pieces of video 24 and 30 fps, and they are of “similar quality”, they will be of different bitrates. If they are of similar bit-rates, they will be of different quality (the 24 will be of better quality). Is that hard to understand?In other words, it is not possible (with the same encoder) to create two films, 24 and 30 frames that have similar bitrate and similar quality. Either they will have similar bitrate (and the 24 fps will be of higher quality) or they will have different bitrate (24 fps will be lower) and they will be of similar quality.
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Do you mind explaining a bit more?
Why would 24p video at the same bitrate as 30i video be of higher quality than the 30i video? Is it because of the 30i video has 25% more info than the 24p video, and therefore would require a bitrate 25% higher to achieve equal quality?
What my experience showed me was that a 24p piece of video encoded with a CBR of 6,000,000 was in fact *larger* in size than a 30i piece of the same video, same length, encoded with the same CBR. Later tests showed me that the rendered file, in fact, had a larger average bitrate than the encoder was set to — which makes me wonder how Vegas determines bitrates if they end up, in actuality, being different than the CBR…
This whole thing started after I completed a 24p project and rendered it as a DVD Architect mpeg, using default settings. For grins, I decided to render the project as a 30i DVD Architect mpeg (again, default settings) to see what size it would end up being. I expected it to be significantly larger in than the 24p mpeg because Sony’s help files say that “24p video uses less space on a DVD, allowing you to add more video or use higher-quality video than you could with 30i video”. I read this to mean that, all things being equal (default settings/bitrates vs. default settings/bitrates — the only standard for quality I could think of), a 24p video would be smaller than 30i.
But what I’m understanding from you now is that a 6,000,000 CBR 24p video is in fact of *higher* quality than 30i, because it contains 20% less data than a 30i file and therefore is using the same bitrate for *less* data, resulting in higher quality. Am I following you correctly?!
Thanks for your time……. This has been an education in bitrates, to say the least.. 😉
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Why would 24p video at the same bitrate as 30i video be of higher quality than the 30i video?
The bitrate is a measure of how much information is being used to create a time period of video, for example 1 second. Assume 1 second of video at a bitrate of 5MB pr second. If you have 1 frame/second the encoder has the ability to use the entire 5MB to paint that one frame. If you have 30 frames in the same second, each frame can obviously have less data (1/30th of the 5MB available), and will therefore be of lower quality. This is overly simplistic, but close enough.
The more frames/second your vide has, the higher the bitrate has to be to create the same quality of each individual frame.
That your 24 fps video was larger was due to the fact that it had a higher bitrate. Calculating the bitrate when the encoder is creating a video file will never be 100% accurate. It is difficult for the encoder to know exactly how well your video can be compressed.
But what I’m understanding from you now is that a 6,000,000 CBR 24p video is in fact of *higher* quality than 30i, because it contains 20% less data than a 30i file and therefore is using the same bitrate for *less* data, resulting in higher quality. Am I following you correctly?!
You are following me correctly.
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This all makes perfect sense. But it raises a new question… and I’m just kinda thinking out loud here…..
When I encode a 24p DVD Architect mpeg stream (with default settings), a post-render analysis shows the bitrate to be in the 7.4 range…. When I encode the same video as a 30i DVDA stream, the same analysis shows the video to be in the 5.9 range, roughly. This causes the 24p file to end up *slightly* larger than the 30i file. Of course, I’d assume the quality is vastly higher with the 24p file, based on the principles we’ve discussed. So I wonder if Vegas, as a default, knowingly encodes 24p at such a high bitrate to take advantage of the opportunity for a higher quality final product?
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