• New Patreon Tier and Early Access Content available. If you would like to support AVForums, we now have a new Patreon Tier which gives you access to selected news, reviews and articles before they are available to the public. Read more.

x.264 vs h.264 - So What's The Difference?

EViS

Active Member
I'm really struggling to see what the difference is between x.264 vs h.264 in terms of HD (720P or even 1080P) mkv movies and/or films? What is the preferred format in terms of video/audio quality?

Also does this sounds about right for rips which do NOT show any obivous quality loss (based upon my research so far):

6.00GB mkv @720P = 2hr @ 9.5mbit average video bitrate. 6mbit average video bitrate is sufficient.
13.5GB mkv @1080P = 2hr @ 14.5mbit average video bitrate. 8-12mbit average video bitrate is sufficient.
 

EViS

Active Member
Right, does this mean that x.264 is the answer to Blu-Ray/HD-DVD compression that divx is to DVD?

Or is the above quite incorrect and x.264 (being one of the three BD codecs) is also used when ripping a Blu-Ray onto a HDD, except the resolution of bitrate is lowered to fit within a .mkv container?
 

Gadgetcity

Active Member
H.264 is the video codec ie the video format.
x264 is a program to encode H.264 video format. It is available as a "library" so people can add their own user interfaces or even modify the program.
Other programs that can make H.264 include Nero and Quicktime.
You are right about .mkv, it is just a container that holds video and audio together in a file, just the same as .mov does for the Quicktime version.

Hope that makes it clearer.
 

EViS

Active Member
That does indeed, thank you! Does this also mean that my second statement in the above reply is also correct?

And, is there any reason why Newzbin (Usenet) have seperate searches for x.264 and h.264? Surely there should only be a search for h.264 as that is the video format you are looking for and NOT what program the video was encoded with?
 

Gadgetcity

Active Member
It is nearly there. You can make a "perfect" copy of the video and a "perfect" copy of one of the video streams (normally AC3 one) and wrap them in a large mkv
OR
re-encode the video to a smaller size using higher compression (but it will look a little worse) and re-encode the lovely surround sound into a stereo mp3 and wrap that lot up into a smaller, lower quality, mkv
OR
anywhere in between

The most popular seems to be slightly compressed video or even resized video, and the AC3 soundtrack.

Note: Bluray has even higher quality sound on it as well but this takes up a lot of space. That is why the AC3 version is normally used which is identical to DVD.

PS people use x.264 in file names to indicate that the video was compressed using the x.264 program. It is still H.264 format.
 

EViS

Active Member
So the h.264 category should include perfect copy's at 720P/1080P with PCM audio? I can't say I've found this to be the case as movies listed in the h.264 category are often MUCH smaller in size to those in the x.264 category.

Also, what do the studios use to encode movies into h.264? I take it they do not use x.264?
 

Gadgetcity

Active Member
So the h.264 category should include perfect copy's at 720P/1080P with PCM audio? I can't say I've found this to be the case as movies listed in the h.264 category are often MUCH smaller in size to those in the x.264 category.

Also, what do the studios use to encode movies into h.264? I take it they do not use x.264?
Ignore the catagory thing, it means nothing. Some people just use x264 and H.264 interchangeably. People post xvid files as HD but they are sometimes as low as 640x360 - NOT HD!

Studios use several codecs. Paramount have been known to use MPEG2 (ie DVD) on their Blurays. Some have used VC1 (Microsoft call it WMV) and others use a specific version of H.264 (MPEG4 AVC High Profile) and I'm sure they all use very expensive, multipass codecs. Remember, their original source is either film or high resolution digital formats. These will have different requirements to a home PC use.
 

EViS

Active Member
So far so good, now just to double check:

a) The actual codec used to watch HD mkv's (i.e. from usenet) is NOT x264, but a h.264 codec such as CoreAVC?
b) x264 is an encoder only and its design is based on the h.264 standard?
c) x264 is not a codec able to decode a movie/film? Or can it also decode video? I see it appears in the list of codecs in ffdshow...
 

Gadgetcity

Active Member
So far so good, now just to double check as I am getting seriously contradicting explanations of h.264 & x264 from various sources.

a) The actual codec used to watch HD mkv's (i.e. from usenet) is NOT x264, but a h.264 codec such as CoreAVC?
b) x264 is an encoder only and its design is based on the h.264 standard?
c) x264 is not a codec able to decode a movie/film?

I think you've got it. CODEC means COder DECoder. The x264 program is solely for COding to the H.264 standard so yes you don't use it to watch H.264 format video.

Strictly CoreAVC is just a DECoder, but, CODEC has become a term in windows that identifies a driver the Codes and/or Decodes.

Hope that helps!
 

Zarch

Well-known Member
So far so good, now just to double check:

a) The actual codec used to watch HD mkv's (i.e. from usenet) is NOT x264, but a h.264 codec such as CoreAVC?
b) x264 is an encoder only and its design is based on the h.264 standard?
c) x264 is not a codec able to decode a movie/film? Or can it also decode video? I see it appears in the list of codecs in ffdshow...

a) Correct, a codec is the way of decoding a video stream, in this case CoreAVC or ffdshow can decode h264 video.
b) Correct, x264 is a h264 encoder only.
c) Correct, x264 its not a codec. Why does it appear in the ffdshow list? Laziness or covering all bases due to everyone's clouded interpretation of what its doing? ;)
 

EViS

Active Member
That all helps a tremendous amount, thank you very much! Looking back now, I can't see where I got so confused, easy to say once it's figured out though haha.

As we touched on the topic, what is meant by how many passes a video (and audio?) has had? I take it, the more passes the better? Would three passes take three times as long to encode?
 

Gadgetcity

Active Member
As we touched on the topic, what is meant by how many passes a video (and audio?) has had? I take it, the more passes the better? Would three passes take three times as long to encode?

To get the best compression/performance you make two passes. The first just basically makes a note of the stuff in the file so that it can intelligently compress it on the next pass.
 

Gadgetcity

Active Member
Can you make more than two passes? Is there any real benefit?

You only make two. The first pass generates a log/index file to help with the encoding phase. Once you've read the whole file once there is simply no need to read it again apart from actually encoding it. You would normally only do this for variable bit rate files so that you make the best use of the space you have available eg use less space to encode simple images and that frees up space to better encode complicated images.

In summary,

you can encode (single pass)
or
analyse then encode (multipass)
 

EViS

Active Member
Great stuff :). The only reason I asked is because I'm sure I recall seeing nfo's on newzbin stating figures for 3 or even 4 passes in the past... May be imagining it though...
 

Zarch

Well-known Member
Great stuff :). The only reason I asked is because I'm sure I recall seeing nfo's on newzbin stating figures for 3 or even 4 passes in the past... May be imagining it though...

I think you might be recalling standard def stuff that was encoded using CCE, that always was referred to having been created using x number of passes. ;)
 

Gadgetcity

Active Member
Great stuff :). The only reason I asked is because I'm sure I recall seeing nfo's on newzbin stating figures for 3 or even 4 passes in the past... May be imagining it though...

You can have a 3rd pass to analyse the quality of the output AND you can have further passes to improve the trellis and huffman encoding(don't ask) but they are used to optimise the 2nd pass a small amount on some more esoteric codecs, not H.264 as far as I'm aware. It is a bit like the settings in Winzip for compressing files. Quick, standard and High compression. Quick is one pass (in video realtime encoding "streaming" only gets one pass!). Standard is two pass, analyse them write. High is more than 2 pass, you might make the file 0.5% smaller - but it will be the same quality.

Video gets really complicated - it is not just pictures, there is also the tracking of movement and brightness changes between frames being encoded.
I don't think any of the usual codecs do anything other than 1 or 2 pass.
 

Gadgetcity

Active Member
Commercial DVDs are 2 pass
DVD recorders use single pass
:smashin:
 

The latest video from AVForums

Fidelity in Motion's David Mackenzie talks about his work on disc encoding & the future of Blu-ray
Subscribe to our YouTube channel

Full fat HDMI teeshirts

Support AVForums with Patreon

Top Bottom