Posted: 1/15/2006 3:53 PM
Post subject: 60 fps videos...?
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skizm
Joined: 1/15/2006
Posts: 4
i'm not really sure if this has been posted here, but... is there a reason all the videos (at least the ones i have watched) are encoded in 60 fps? dropping half the frames wouldn't really lower the precision of the video... and it would effectively halve the filesize. or double the quality for the same filesize. any thoughts?
Posted: 1/15/2006 4:02 PM
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SXL
Joined: 2/7/2005
Posts: 571
I believe that only differences are encoded into videos (except key frames of course). so, in theory, 60 fps wouldn't be that bigger since the more frames there is, the less differences between frames there is, and smaller difference = smaller size. sorry if that's not clear. earlier movies made on this site were recorded in 30 fps : the video quality was much lower (less smooth), and more important, it was much more difficult for players to pull out tricks, since they had half the number of fps to try things.
I never sleep, 'cause sleep is the cousin of death - NAS
Posted: 1/15/2006 4:02 PM
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DeHackEd
Emulator Coder, Site Developer, Former player
Joined: 11/6/2004
Posts: 833
Besides the fact that the hardware does produce 60 fps and it's "most correct" to show every frame, you just might be amazed what the difference is.
Posted: 1/15/2006 4:43 PM
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skizm
Joined: 1/15/2006
Posts: 4
i meant the encoded multimedia videos ;)
Posted: 1/15/2006 4:43 PM
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DeHackEd
Emulator Coder, Site Developer, Former player
Joined: 11/6/2004
Posts: 833
.. Did you even download the zip?
Posted: 1/15/2006 4:48 PM
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nesrocks
He/Him
Player (246)
Joined: 5/1/2004
Posts: 4096
Location: Rio, Brazil
The tv displays 60 half frames per second (interlaced). What the emulator does is transform each of those half frames a full frame.
aka Nesrocks http://www.youtube.com/user/UoBtExFODA https://nesrocks.com https://twitter.com/bitinkstudios
Posted: 1/15/2006 5:17 PM
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skizm
Joined: 1/15/2006
Posts: 4
DeHackEd wrote:
.. Did you even download the zip?
well, no. i assumed since it says 30fps on it, the 60fps wouldn't be included so i'd have no way of comparing it. i was responding to SXL though ;p and yes, i know how video works, which is why i'm posting here in the first place ;) you're right about the "not really half filesize" thing, i haven't slept yet so my logic is kind of fuzzy at the moment. the filesize would be significantly less though.
Posted: 1/15/2006 5:45 PM
(Edited: 1/15/2006 5:46 PM)
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moozooh
Senior Moderator
Joined: 8/4/2005
Posts: 5777
Location: Away
skizm wrote:
the filesize would be significantly less though
Well I think you should consider watching movies on the emulator itself, since the emulator movie files have as low filesize as you can possibly get. DeHackEd has a good point: the precision. I watched some Super Metroid runs from SDA recently, and they were encoded at 29.97 fps. Every time Samus rode up the elevator, she disappeared. Some shots disappeared, too. It was ugly.
Warp wrote:
Edit: I think I understand now: It's my avatar, isn't it? It makes me look angry.
Posted: 1/15/2006 5:45 PM
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LocalH
Joined: 10/3/2004
Posts: 138
That would be disastrous for NES videos, as many NES games use 60Hz-flickering for various reasons, and dropping half the frames may cause sprites to disappear, depending on whether you drop even or odd frames. Consoles pre-Dreamcast tend to mostly use a 60fps noninterlace mode (although the SNES and Genesis both do support an interlace mode, they weren't used much).
Sonic Retro
Posted: 1/15/2006 5:49 PM
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TNSe
Emulator Coder
Joined: 10/9/2004
Posts: 453
Location: Norway
In addition to all of the above, this site encodes with h264 which has frame drop support. Basically what that means, is that if 2 or more similar frames come in succession, it only stores 1 of them, and tells the decoder to show the same image x amount of times.
Posted: 1/15/2006 5:50 PM
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Bisqwit
Editor, Active player (297)
Joined: 3/8/2004
Posts: 7469
Location: Arzareth
LocalH wrote:
That would be disastrous for NES videos, as many NES games use 60Hz-flickering for various reasons, and dropping half the frames may cause sprites to disappear, depending on whether you drop even or odd frames.
And I believe that's why Famtasia author chose to use 20 fps instead of 30 fps: to make it unlikely that a blinking object doesn't blink. But, if you compare this 20 fps movie (Super Mario Bros 2): http://tasvideos.org/movies.cgi?id=10 with this 60 fps movie (Super Mario Bros 2): http://tasvideos.org/movies.cgi?id=400 You should notice a very obvious difference in the animation quality. I don't have a 30 fps example here, but have a look at Dehacked's sample. Disclaimer: Not all people notice it.
Posted: 1/15/2006 6:09 PM
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Maza
Joined: 5/27/2005
Posts: 465
Location: Turku, Finland
After watching DeHackEd's 30fps version and comparing it to 60fps version, I definitely think we should stick to 60fps. Even thou' the size of the movie is somewhat bigger.
Which run should I encode next? :)
Posted: 1/15/2006 6:23 PM
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skizm
Joined: 1/15/2006
Posts: 4
perhaps you're right, then. my apologies ;) i don't watch the videos on an emulator though, because i don't really have easy access to the roms. i could find them, but it's more effort than i'm willing to put forth ;p and i wasn't asking in my own interest. the videos have reasonable filesizes for me, i download 200+ meg files every day : / i pretty much was thinking about the "torrent admin" being able to save bandwidth. but it doesn't really sound like a good idea after all ;)
Posted: 1/15/2006 6:57 PM
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Dada
Joined: 11/22/2004
Posts: 1468
Location: Rotterdam, The Netherlands
It makes absolutely no difference in filesize whatsoever to encode videos in 30 FPS rather than 60 FPS. I made a 20 FPS encode of a speedrun I made one time at a low quality setting. It was to be an ultra-low bandwidth version. However, the 20 FPS version was almost the exact same size as the 60 FPS version, both at the same quality! x264 is smart and has excellent motion compensation.
Posted: 1/19/2006 12:31 AM
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Warp
Banned User
Joined: 3/10/2004
Posts: 7698
Location: Finland
People have a (reasonable) misconception that doubling the image size will double the size of the file where the image is stored, and doubling the number of frames in a movie will double the size of the movie file. Testing different-sized images saved as JPEG seems to about corroborate this (even though you probably don't need to double the size of the file in order to get the same visible quality, but the size of the file increases notably nevertheless). Although that is intuitive, MPEG-4 doesn't really work that way (it's probably the same with MPEG-2; I'm not sure about MPEG-1 - there you probably will have to increase file size noticeably). According to my own tests (which I made many years ago), increasing the resolution of the video while keeping the same filesize (of the resulting MPEG-4 file) will actually *increase* the image quality instead of decreasing it. Not much, but some. In the same way increasing the framerate while keeping the same file size will most probably only have a positive effect on the image quality. You can probably think about it like "increasing resolution or framerate will give the encoder more data to work with and create a higher-quality result while keeping the same file size". Of course there are most probably some limits. You probably can't expect to keep the same image quality if you compare a 512x384 video and a 16000x12000 version of the same video with the same file size. However, with practical resolutions it indeed seems to be so that bigger resolution gives better image quality without needing more space.