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| Porn Users Forum » Bitrates! |
| 1-11 of 11 Posts | Page 1 |
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| 09-04-08 01:56pm - 5953 days | Original Post - #1 | |
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messmer (0)
Disabled User  Posts: 2,582 Registered: Sep 12, '07 Location: Canada |
Bitrates! How come an HD video in wmv can be at 8000 kbps while an avi video also in HD can show a bitrate of only 192 kbps. And why can some wmv files weighing in at 2000 kbps look like crap while other wmv files with the same bitrate look like HD? I am baffled and am looking for a layman's answer as to the function of a bitrate. I think someone in this group took on the impossible task of enlightening me a couple of months ago and it didn't take .. but maybe if someone else kept it real simple. Thanks! :-) | |
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| 09-04-08 03:58pm - 5953 days | #2 | |
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badandy400 (0)
Active User  Posts: 869 Registered: Mar 02, '08 Location: ohio |
It really depends on how it is shot and how it is filtered and compressed. That really is all there is to it. It is kinda like comparing a barrel of gun powder to a small nuke. They are the same size, but because someone put better stuff into the nuke it is significantly stronger. So you are correct about a 2 MBit video looking better or worse depending on where you get it. When something is compressed they are basically removing information from the picture, ideally it is information that is not needed for the picture to maintain quality. If the visible light spectrum is between 400 and 700 nanometers than data on "light" at 780 nanometers is worthless to us humans, therefore it should be removed. Since not every bit of data goes into making a visible picture it depends on how much of that inert data is removed. Someone good can remove enough to make a 2 MBit video look as good as someone else's 3 MBit video for example. Then there is the matter of filtering. Filtering videos correctly can yield a nicer picture by removing "noise" from the video. I am not an expert on any of this, so if someone has a better explanation please provide it! Basically what it comes down to is how much money someone is willing to spend on creating the picture and how much effort they are will to put forth. "For example, badandy400 has taken it upon himself to become the one man Library of Congress for porn with a collection that surely will be in Guinness Book of World Records some day." ~Toadsith~ PU Interview | |
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| 09-04-08 06:00pm - 5953 days | #3 | |
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messmer (0)
Disabled User Posts: 2,582 Registered: Sep 12, '07 Location: Canada |
Thanks a lot, badandy, that explains a lot about the differences between videos who are superficially of the same quality, 2000 kbps. I am still curious about the avi video. Why such a dramatic difference and how can the picture be crystal clear at 192 kbps? Any idea? | |
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| 09-04-08 07:42pm - 5953 days | #4 | |
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badandy400 (0)
Active User Posts: 869 Registered: Mar 02, '08 Location: ohio |
192 is likely the audio bitrate. Make sure that is not what it is. How big is the actual file and how long is the video? If it is the video bitrate that would mean that a 10 minute video would be 14.4 MB. 192 is a typical bit rate for MP3s and other audio files, a video with that bitrate would be practically unwatchable. "For example, badandy400 has taken it upon himself to become the one man Library of Congress for porn with a collection that surely will be in Guinness Book of World Records some day." ~Toadsith~ PU Interview | |
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| 09-05-08 06:54am - 5952 days | #5 | |
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messmer (0)
Disabled User Posts: 2,582 Registered: Sep 12, '07 Location: Canada |
The video I picked at random this morning is 472.011 KB in size and about 55 minutes in length with a bitrate around 380, badandy. | |
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| 09-05-08 12:53pm - 5952 days | #6 | |
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badandy400 (0)
Active User Posts: 869 Registered: Mar 02, '08 Location: ohio |
There is something seriously wrong with that number. Is it some sort of link to a string? If you said 472 MB it would believable. Where did you get this video from? "For example, badandy400 has taken it upon himself to become the one man Library of Congress for porn with a collection that surely will be in Guinness Book of World Records some day." ~Toadsith~ PU Interview | |
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| 09-05-08 01:15pm - 5952 days | #7 | |
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messmer (0)
Disabled User Posts: 2,582 Registered: Sep 12, '07 Location: Canada |
I forgot to mention that this low number only shows up on avi and rm files, badandy. | |
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| 09-05-08 02:15pm - 5952 days | #8 | |
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Toadsith (0)
Active User  Posts: 936 Registered: Dec 07, '07 Location: USA |
My guess is that file links to a streaming video. If your player is reporting the bitrate correctly at 380 kilobits per second and the length is 55 minutes exactly then the math for estimating it's size goes like this: 1 kilobit = 1024 bits 380 kilobits = 389120 bits 55 minutes = 3300 seconds 55 minutes at 380 kbps = 1,284,096,000 bits 1 byte = 8 bits 1,284,096,000 bits = 160,512,000 bytes 1 kilobyte = 1024 bytes 1 megabyte = 1024 kilobytes 160,512,000 bytes =~ 153.1 megabytes Of course, that is just the video data - the audio data would probably be another 20 megabytes. So the actual file should be in the 175MB range. None-the-less, for an hour video that is a small file. Even using high compression DivX, that is still going to be a pretty fuzzy looking picture. If the file were really only 472KB for 55 minutes, it would end up looking like porn rendered by an Atari 2600. Even 2 hour movies encoded for tiny cellphone screens tend to be over 100MB. At any rate, back on your original question: Not only do the compression softwares like to remove all non-visible light for humans like badandy was mentioning, but they also like to merge same color areas together and remove subtle detail in dark shadows or bright whites. Water is often a big pain-in-the-ass for encoding software as it can cover much of the screen and have incredibly complex, changing patterns that simply cannot be compressed without losing detail. Another very simple trick is anytime the image is still, rather than saving 240 unique frames for a 10 second title card (or 300 for standard video) - the program will save one frame and then instruct the computer to display it for 10 seconds. One of the big innovations that set DivX apart from other encoding software back in the day was the use of key frames. Every time the video changed significantly enough it would capture a full resolution frame. The key frame is the starting point, for the next frame all DivX would record was the difference between that frame and the key frame. This way full frames would only comprise a small portion of the file and the rest of the video's frames would be rendered from those key frames using the instructions in the file. In a sense, it uses the same compression ideal that makes vector drawings so small. It takes less space to tell the computer how to render an image using maths than it does to tell the computer what color each pixel should be. "I'm not a number, I'm a free man!" Second Grand Order Poobah in the Loyal Order of the Water Buffalo | |
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| 09-05-08 03:08pm - 5952 days | #9 | |
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atrapat (0)
Active User  Posts: 182 Registered: Apr 19, '08 Location: Non-USA |
I believe you are using the dot in 472.011 as thousands separator, so 472.011 KB =~ 460 MB. I'm no expert in this matter but, in my experience, windows explorer "lies" about bitrates when it comes to divx files. For instance, I have a particular file that windows says is a 4kbps file; it's in fact a divx with more than OK quality. My guess is that divx/xvid codecs might be using some variable bitrates and that's what fools windows. I tried my 4kbps file on GSpot (handy program for getting lots of info on a particular video file). It took some time but eventually said it was 800 kbps on average. According to the 55 min duration and the 460 MB file size, I'm guessing your sample file is an avi file encoded with variable bit rate which windows mistakenly reports as 192 kbps. The average bit rate for this file should obviously be higher than 192 kbps. | |
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| 09-06-08 02:37pm - 5951 days | #10 | |
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messmer (0)
Disabled User Posts: 2,582 Registered: Sep 12, '07 Location: Canada |
Thanks, toadsith and atrapat I think atrapat nails it with his observation of Windows (in my case Vista) making mistakes. That is the most likely explanation because I've tried the sample video off-line and it doesn't attempt to link to any streaming site and works perfectly with modem in sleep mode. I also find that while I would get the duration of a wmv video listed when I still used Windows xp I no longer get it with Vista. So let's blame Vista and Microsoft. Thanks, guys! | |
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| 09-07-08 04:45pm - 5950 days | #11 | |
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Toadsith (0)
Active User Posts: 936 Registered: Dec 07, '07 Location: USA |
Vista is evil! "I'm not a number, I'm a free man!" Second Grand Order Poobah in the Loyal Order of the Water Buffalo | |
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