4K videos

[Ozz]

Are you suggesting that H.264 and H.265 somehow store frames dependently?

Hi - You can think of MP4 as being a series of JPGs - but to store every frame (24 or 60 per second) as JPG frames in one file would be a Huge file - so it stores One JPEG (called the IFrame) and then for each frame after it only records the Difference- which might not be much at all. Every few seconds it will start again with a new IFrame, followed by differences.
So yeah - every frame after the full IFrame is dependent on the previous frame.

This means that if you Rewind a file or jump to any random point in the video - it will have to go to the last closest I-Frame to where you want to jump to - and internally go through and build up the frame you want from the differences. This makes rewinding smoothly very difficult for software - Some software is better than others at doing this (Apple computers do this really well).

You can see this sometimes when you see a video breaking up oddly and it corrects itself suddenly after it displays the next full IFrame.

As Thomas has said - The prores format is all IFrames Only - no differences - no dependant frames - so you can rewind and jump easily to any point in the file immediately. Just like any video, all the frames are stored in one file - one after the other - just a very long file (split sometimes if the os has limitations on file size).

Now its all more complex than that - but thats the idea - and Thomas' links go into detail.

 

[gr8pics]

So

Hi - You can think of MP4 as being a series of JPGs - but to store every frame (24 or 60 per second) as JPG frames in one file would be a Huge file - so it stores One JPEG (called the IFrame) and then for each frame after it only records the Difference- which might not be much at all. Every few seconds it will start again with a new IFrame, followed by differences.
So yeah - every frame after the full IFrame is dependent on the previous frame.

This means that if you Rewind a file or jump to any random point in the video - it will have to go to the last closest I-Frame to where you want to jump to - and internally go through and build up the frame you want from the differences. This makes rewinding smoothly very difficult for software - Some software is better than others at doing this (Apple computers do this really well).

You can see this sometimes when you see a video breaking up oddly and it corrects itself suddenly after it displays the next full IFrame.

As Thomas has said - The prores format is all IFrames Only - no differences - no dependant frames - so you can rewind and jump easily to any point in the file immediately. Just like any video, all the frames are stored in one file - one after the other - just a very long file (split sometimes if the os has limitations on file size).

Now its all more complex than that - but thats the idea - and Thomas' links go into detail.

So, you say that a mp4 file recorded in 24fps cant be scrolled trough frame by frame counting 24 frames per second like a Prores file with same fps?
Or are you saying the 24 frames per second in a mp4 file is not the same as the 24 frames in a Prores file?
I would love to hear the explanation in plain english, and not trough links, if you dont mind.

 

[smiller]

Ozz's description is about as close to 'plain English' as you are going to get. There is no way to completely describe what goes on during video coding in a few sentences or paragraphs, it is an extremely complex process.

 

[gr8pics]

Ozz's description is about as close to 'plain English' as you are going to get. There is no way to completely describe what goes on during video coding in a few sentences or paragraphs, it is an extremely complex process.

I think this might be a little confusing in this context, how a Prores saving procedure works alone is irrelevant here, since original format has a lower quality (heavier compression) than Prores itself, therefore you cannot gain better quality just cause you convert to Prores, only minimize further loss of quality, depending on the Prores profile used.
Each frame in a mp4 file will still be almost as good as each frame in the Prores file after conversion...
Every 24 frame in the mp4 file will be equal or have less quality after converting it to Prores, it is only the optimized format Prores that makes it easier to work with in post, and does not give you any better quality, its only less worse, thats whats matter in the end here.

If you want to maintain as much of the already "poor" quality in a mp4 file as you can, you need to use a 444 profile, and not 422, as it will throw away yet another "half" of the color space, but 444 uses a ridiculous amount of space, so you end up using 422.
After finishing in post and you save back to mp4, you will lose even more quality, you will suffer further quality loss, but it's because of the mp4 -> mp4 re-encoding.
Put more simply, the:
mp4 -> ProRes422 - mp4
will not look any worse than:
mp4 -> mp4
Thats why its best to save the final product as Prores(.mov) and use that for upload to YT or Vimeo.

Back to Thomas orignal statement "however all frames are stored independently"
The correct description should be "however all frames are ENCODED independently" and thats a big difference...

 

[Ozz]

There are some apps out there that can edit MP4 and JPEGS files Losslessly.

I've used TVREDO to clip out parts of long videos - it reassembles the file then with no loss at all in quality, .
It does it by clever use of the IFrames.
So no reencoding and the additional benefit of this is that it takes just seconds to export a finished file with all the unnecessary bits removed - even on a low power pc.

For JPEG editing - using ACDSEE - I can rotate images without reencoding the jpeg - otherwise you loose image quality evertime you edit and save an image.
I'm sure there are more modern software but thats what I still use.

There also used to be tools that can crop jpegs without reencoding and loosing quality.

 

[GadgetGuy]

Hi - You can think of MP4 as being a series of JPGs - but to store every frame (24 or 60 per second) as JPG frames in one file would be a Huge file - so it stores One JPEG (called the IFrame) and then for each frame after it only records the Difference- which might not be much at all. Every few seconds it will start again with a new IFrame, followed by differences.
So yeah - every frame after the full IFrame is dependent on the previous frame.

This means that if you Rewind a file or jump to any random point in the video - it will have to go to the last closest I-Frame to where you want to jump to - and internally go through and build up the frame you want from the differences. This makes rewinding smoothly very difficult for software - Some software is better than others at doing this (Apple computers do this really well).

You can see this sometimes when you see a video breaking up oddly and it corrects itself suddenly after it displays the next full IFrame.

As Thomas has said - The prores format is all IFrames Only - no differences - no dependant frames - so you can rewind and jump easily to any point in the file immediately. Just like any video, all the frames are stored in one file - one after the other - just a very long file (split sometimes if the os has limitations on file size).

Now its all more complex than that - but thats the idea - and Thomas' links go into detail.

Thanks for that clarification!

 

[Pete Martson]

Ok here's the deal. This footage straight out of your bird is raw and not COMPRESSED. It's raw 4K. So it would take forever to load this stuff in that form. And it would never play smooth because it is so processor demanding. Here's a link to all settings that work best for Youtube here. Recommended upload encoding settings - YouTube Help But rendering in a video editor is going to compress and smooth your file and make it a feasible size to upload to Youtube. It's hard enough for a smoking good computer processor and video card to play these files smoothly while they are still RAW 4K. So can you imagine what's it's like trying to stream this kind of footage from the net through Youtube??

First of all, footage from the P4P IS compressed in either h.264 or h.265. The P4P does not do RAW video. Second, YouTube DOES stream 4K video.

 

[KevMo Photog]

First of all, footage from the P4P IS compressed in either h.264 or h.265. The P4P does not do RAW video. Second, YouTube DOES stream 4K video.

My terminology is off base here Pete. Thx for clearing that up. Video is new to me in last year or so. I guess what Im trying to say that it's raw in that it has not rendered out for posting yet. And yes, Youtube def streams 4K but you better have a smoking hot connection to play it worth watching. I have Comcast for 55 bucks or so a month. And it rarely plays 4K perfectly.

 

[bluntnose]

Will prores and tvredo run on my apple equipment?

Interesting thread, I learned a bunch.


Sent from my iPad using PhantomPilots