Omnipresence of H264 is a fact : BluRay, Youtube, Sony’s XAVC, Panasonic’s AVC-Ultra or Canon’s XF-AVC. It’s indeed the most versatile codec of the compression’ history.
Let’s have a look to its numerous subtleties. Attention le cerveau va chauffer! Ce article est la suite de “MPEG-4 Mon amour”, que je vous invite à (re)-lire.
We can find it along digital video’s workflow :
From shooting : AVCHD, NXCAM (Sony), XAVC (Sony) AVCCAM (Panasonic), AVC-Intra (Panasonic), (AVC-Ultra (Panasonic) .
to professional broadcasting : BluRay (.m4v or .264 files) BluRay 3D (.mvc files)
to online streaming : Youtube/Vimeo/ either Flash or HTML5
to broadcasting for Pads and Mobiles : iDevices (iPad, iPod, iPhone)
To home multimedia center : Apple TV or TVIX or Popcorn Hour
Profils & Levels
There is a various types of H264. To get around, we can do 2 subdivision :
- the level is referring to a size and a maximal image frequency.
- The profiles are referring to the complexity of the algorithms used to compres/decompres. It would be saying that there are different level of effeciencies of H264 compression. 3 mains profiles are : Base, Main et High.
Either a similar quality of image for a compression rate +/- important or a better quality for the same compression rate. Then a low efficiency is simpler to decode = power savings….
- Baseline : for ipod and Iphone (to iPhones 3)
- Main (CABAC and B frame) : for Ipad 1&2, Apple TV 2 and Iphone 4
- High (Macrobloc de 4×4, monochrome 4:0:0) : Computer
- High 422 Intra : Panasonic’s AVC-Intra
Video cameras’ H264s
We can see that Sony and Panasonic renamed their AVCHD (High@L4.0) in NXCAM and AVCCAM to be sure not confusing them with AVCHD (Main@L4.0) which can be poor quality because to the maximal debit of 20 Mbps.
In most cases AVCHD High@4.0 has 24Mbps and is well used and good quality.
The last (November 2011) specification of AVCHD 2.0 brought l « AVCHD Progressive » (High@L4.2) for the la Full HD in 50/60 fps and l « AVCHD 3D » for stereocopy in Full HD à 25/30 fps
Advanced H264 Compression
You can have a look at the article about basics of compression
Even if the futur is already here with H265 or HEVC (High Efficience Video Coding) codec, H264 still has good days to come due to its hegemony and popularity on many devices