Friday, 8 February 2013

4K codecs - the good, the big and the ugly. Part 1

There can be little doubt that there is going to be a huge increase in the demand for 4K footage over the next few years and much of that early demand will have to satisfied by stock material. Currently broadcasters can turn to an enormous library of SD and HD material compiled over decades of shooting, but that won't cut the mustard when intercut with newly acquired 4K footage.

Which is good news for those of us who are planning on making our own library of high quality 4K stock shots. One question I would love to answer is which flavour of 4K will be the choice of stock libraries and I really hope that the big boys can come to some sort of agreement here, because uploading four different versions of a 4K clip is not a quick process.

Now H.265 has been announced and I think this will become the bookies favourite even though its younger cousin H.264 is not currently stock libraries first choice for progressive footage. But efficient as H.265 is, it's unlikely to be a good format to edit with for reasons I won't go into here. This means any stock footage will have to be transcoded to another format or codec before editing.

So I ran some tests on existing codecs using a 4K clip from a time lapse within Adobe After Effects to see if any of them would be good enough to host on the web and edit with natively. Here is a still from the sequence. 

The One Tower, St Georges Wharf, Vauxhall, London
The crane on the tall building behind Vauxhall Bridge was unfortunately hit by a helicopter in January 2013 in case it looks familiar - you can see a 1080p version of the time lapse here. I chose this clip because of the complexity of the image with lots of vertical and horizontal lines and a lot of detail in the sky and water.

Here are the codec candidates:

Avid DNxHD - works on Mac and PC and the codec is free.
BlackMagic codec - great quality but probably too big and not widely used.
Cineform - again works on Mac and PC but you need the Premium version of Cineform Studio to create files and this is $299.
Photo JPEG - An old codec, with good compatibility. Currently the choice of many stock companies but not the most efficient of compression choices.
TIFF - Using LZW compression should give a perfect image but with file sizes to match. Also tried a QT using TIFF.
Animation - Not used so much any more but moving between editing and graphics tools is used to be the king. Huge differences in file size depending on the compression ratio.
MPEG A & B - Had their day I think and largely used only for interlaced  
ProRes - A really great codec but will not play well (if at all) on PCs, which really is a ridiculous situation. If it did this would be numero uno. I'm working on a PC so couldn't produce any test results. Pah!

I created a 4K (4096x2304) 1 second clip in each format at two or three compression settings (75%, 90% & 100% where possible) to look at file size and quality. Here are the results:

File sizes of  1 second 4K clip in various codecs 
The TIFF sequence adds up to 288 MB for the 25 frames. 

Unsurprisingly the uncompressed or lossless compression codecs are significantly larger than the lossy compressed versions. The embedded TIFF QTs were significantly larger than the sequence of stills using the LZW lossless compression and the TIFF sequence would still be a good way to exchange between editing and graphic systems.

The lossy compression codecs start with Cineform (100% quality) at 126 MB for a 1 second clip. Bearing in mind that the maximum  length of a clip on iStock is 30 seconds and you could end up with a files of 3.78 GB! At 75% quality it would be a mere 1.8 GB

The tests showed that DNxHD 444 10 bit was almost the same size at 100%, 90% and 75%. Somewhat surprisingly it made little difference on MJPEG codecs whether 75% or 90% compression was chosen. But Cineform at 100% jumped up to 126 MB - almost double the 90% file size, which shows remarkably efficient compression if the quality stands up.

Photo JPEG and MPEG4 also showed a big difference between 75% and 90% and a 30 second clip at the higher compression (75% quality) would be just over 1 GB in size.

In Part 2 of this blog I look at the picture quality of the smaller files to see whether they have a future as a 4K stock format.

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